1
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Mellouk A, Jaouen P, Ruel LJ, Lê M, Martini C, Moraes TF, El Bakkouri M, Lagüe P, Boisselier E, Calmettes C. POTRA domains of the TamA insertase interact with the outer membrane and modulate membrane properties. Proc Natl Acad Sci U S A 2024; 121:e2402543121. [PMID: 38959031 DOI: 10.1073/pnas.2402543121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2024] [Accepted: 05/22/2024] [Indexed: 07/04/2024] Open
Abstract
The outer membrane (OM) of gram-negative bacteria serves as a vital organelle that is densely populated with OM proteins (OMPs) and plays pivotal roles in cellular functions and virulence. The assembly and insertion of these OMPs into the OM represent a fundamental process requiring specialized molecular chaperones. One example is the translocation and assembly module (TAM), which functions as a transenvelope chaperone promoting the folding of specific autotransporters, adhesins, and secretion systems. The catalytic unit of TAM, TamA, comprises a catalytic β-barrel domain anchored within the OM and three periplasmic polypeptide-transport-associated (POTRA) domains that recruit the TamB subunit. The latter acts as a periplasmic ladder that facilitates the transport of unfolded OMPs across the periplasm. In addition to their role in recruiting the auxiliary protein TamB, our data demonstrate that the POTRA domains mediate interactions with the inner surface of the OM, ultimately modulating the membrane properties. Through the integration of X-ray crystallography, molecular dynamic simulations, and biomolecular interaction methodologies, we located the membrane-binding site on the first and second POTRA domains. Our data highlight a binding preference for phosphatidylglycerol, a minor lipid constituent present in the OM, which has been previously reported to facilitate OMP assembly. In the context of the densely OMP-populated membrane, this association may serve as a mechanism to secure lipid accessibility for nascent OMPs through steric interactions with existing OMPs, in addition to creating favorable conditions for OMP biogenesis.
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Affiliation(s)
- Abdelkader Mellouk
- Institut National de la Rechyuerche Scientifique (INRS), Centre Armand-Frappier Santé Biotechnologie, Laval, QC H7V 1B7, Canada
- Regroupement Québécois de recherche sur la fonction, la structure et l'ingénierie des protéines (PROTEO), Université du Québec à Montréal, Montréal, QC H2X 3Y7, Canada
| | - Paul Jaouen
- Regroupement Québécois de recherche sur la fonction, la structure et l'ingénierie des protéines (PROTEO), Université du Québec à Montréal, Montréal, QC H2X 3Y7, Canada
- Faculty of Medicine, Department of Ophthalmology and Otolaryngology-Head and Neck Surgery, centre hospitalier universitaire de Québec, Université Laval, Québec City, QC G1S 4L8, Canada
| | - Louis-Jacques Ruel
- Regroupement Québécois de recherche sur la fonction, la structure et l'ingénierie des protéines (PROTEO), Université du Québec à Montréal, Montréal, QC H2X 3Y7, Canada
- Département de Biochimie, de Microbiologie et de Bio-informatique, Université Laval, Québec City, QC G1V 0A6, Canada
- Institut de Biologie Intégrative et des Systèmes, Université Laval, Québec City, QC G1V 0A6, Canada
| | - Michel Lê
- Institut National de la Rechyuerche Scientifique (INRS), Centre Armand-Frappier Santé Biotechnologie, Laval, QC H7V 1B7, Canada
- Regroupement Québécois de recherche sur la fonction, la structure et l'ingénierie des protéines (PROTEO), Université du Québec à Montréal, Montréal, QC H2X 3Y7, Canada
| | - Cyrielle Martini
- Institut National de la Rechyuerche Scientifique (INRS), Centre Armand-Frappier Santé Biotechnologie, Laval, QC H7V 1B7, Canada
- Regroupement Québécois de recherche sur la fonction, la structure et l'ingénierie des protéines (PROTEO), Université du Québec à Montréal, Montréal, QC H2X 3Y7, Canada
| | - Trevor F Moraes
- Department of Biochemistry, University of Toronto, Toronto, ON M5G 1M1, Canada
| | - Majida El Bakkouri
- National Research Council Canada, Human Health Therapeutics, Montréal, QC H4P 2R2, Canada
| | - Patrick Lagüe
- Regroupement Québécois de recherche sur la fonction, la structure et l'ingénierie des protéines (PROTEO), Université du Québec à Montréal, Montréal, QC H2X 3Y7, Canada
- Département de Biochimie, de Microbiologie et de Bio-informatique, Université Laval, Québec City, QC G1V 0A6, Canada
- Institut de Biologie Intégrative et des Systèmes, Université Laval, Québec City, QC G1V 0A6, Canada
| | - Elodie Boisselier
- Regroupement Québécois de recherche sur la fonction, la structure et l'ingénierie des protéines (PROTEO), Université du Québec à Montréal, Montréal, QC H2X 3Y7, Canada
- Faculty of Medicine, Department of Ophthalmology and Otolaryngology-Head and Neck Surgery, centre hospitalier universitaire de Québec, Université Laval, Québec City, QC G1S 4L8, Canada
| | - Charles Calmettes
- Institut National de la Rechyuerche Scientifique (INRS), Centre Armand-Frappier Santé Biotechnologie, Laval, QC H7V 1B7, Canada
- Regroupement Québécois de recherche sur la fonction, la structure et l'ingénierie des protéines (PROTEO), Université du Québec à Montréal, Montréal, QC H2X 3Y7, Canada
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2
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Hartojo A, Doyle MT. β-barrel membrane proteins fold via hybrid-barrel intermediate states. Curr Opin Struct Biol 2024; 87:102830. [PMID: 38728831 DOI: 10.1016/j.sbi.2024.102830] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2024] [Revised: 03/15/2024] [Accepted: 04/22/2024] [Indexed: 05/12/2024]
Abstract
Gram-negative bacteria and eukaryotic organelles of bacterial origin contain outer membrane proteins that possess a transmembrane "β-barrel" domain. The conserved β-barrel assembly machine (BAM) and the sorting and assembly machine (SAM) are required for the folding and membrane insertion of β-barrels in Gram-negative bacteria and mitochondria, respectively. Although the mechanisms by which β-barrels are folded are incompletely understood, advances in cryo-electron microscopy (cryo-EM) have recently yielded unprecedented insights into their folding process. Here we highlight recent studies that show that both bacterial and mitochondrial β-barrels fold via the formation of remarkable "hybrid-barrel" intermediate states during their interaction with the folding machinery. We discuss how these results align with a general model of β-barrel folding.
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Affiliation(s)
- Alfred Hartojo
- Sydney Infectious Diseases Institute, The University of Sydney, Darlington, New South Wales, Australia; School of Medical Sciences, Faculty of Medicine and Health, The University of Sydney, Darlington, New South Wales, Australia. https://twitter.com/AlfredHartojo29
| | - Matthew Thomas Doyle
- Sydney Infectious Diseases Institute, The University of Sydney, Darlington, New South Wales, Australia; School of Medical Sciences, Faculty of Medicine and Health, The University of Sydney, Darlington, New South Wales, Australia.
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3
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George A, Patil AG, Mahalakshmi R. ATP-independent assembly machinery of bacterial outer membranes: BAM complex structure and function set the stage for next-generation therapeutics. Protein Sci 2024; 33:e4896. [PMID: 38284489 PMCID: PMC10804688 DOI: 10.1002/pro.4896] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Revised: 12/28/2023] [Accepted: 12/31/2023] [Indexed: 01/30/2024]
Abstract
Diderm bacteria employ β-barrel outer membrane proteins (OMPs) as their first line of communication with their environment. These OMPs are assembled efficiently in the asymmetric outer membrane by the β-Barrel Assembly Machinery (BAM). The multi-subunit BAM complex comprises the transmembrane OMP BamA as its functional subunit, with associated lipoproteins (e.g., BamB/C/D/E/F, RmpM) varying across phyla and performing different regulatory roles. The ability of BAM complex to recognize and fold OM β-barrels of diverse sizes, and reproducibly execute their membrane insertion, is independent of electrochemical energy. Recent atomic structures, which captured BAM-substrate complexes, show the assembly function of BamA can be tailored, with different substrate types exhibiting different folding mechanisms. Here, we highlight common and unique features of its interactome. We discuss how this conserved protein complex has evolved the ability to effectively achieve the directed assembly of diverse OMPs of wide-ranging sizes (8-36 β-stranded monomers). Additionally, we discuss how darobactin-the first natural membrane protein inhibitor of Gram-negative bacteria identified in over five decades-selectively targets and specifically inhibits BamA. We conclude by deliberating how a detailed deduction of BAM complex-associated regulation of OMP biogenesis and OM remodeling will open avenues for the identification and development of effective next-generation therapeutics against Gram-negative pathogens.
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Affiliation(s)
- Anjana George
- Molecular Biophysics Laboratory, Department of Biological SciencesIndian Institute of Science Education and ResearchBhopalIndia
| | - Akanksha Gajanan Patil
- Molecular Biophysics Laboratory, Department of Biological SciencesIndian Institute of Science Education and ResearchBhopalIndia
| | - Radhakrishnan Mahalakshmi
- Molecular Biophysics Laboratory, Department of Biological SciencesIndian Institute of Science Education and ResearchBhopalIndia
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4
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Gopinath A, Rath T, Morgner N, Joseph B. Lateral gating mechanism and plasticity of the β-barrel assembly machinery complex in micelles and Escherichia coli. PNAS NEXUS 2024; 3:pgae019. [PMID: 38312222 PMCID: PMC10833450 DOI: 10.1093/pnasnexus/pgae019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/09/2023] [Accepted: 01/08/2024] [Indexed: 02/06/2024]
Abstract
The β-barrel assembly machinery (BAM) mediates the folding and insertion of the majority of outer membrane proteins (OMPs) in gram-negative bacteria. BAM is a penta-heterooligomeric complex consisting of the central β-barrel BamA and four interacting lipoproteins BamB, C, D, and E. The conformational switching of BamA between inward-open (IO) and lateral-open (LO) conformations is required for substrate recognition and folding. However, the mechanism for the lateral gating or how the structural details observed in vitro correspond with the cellular environment remains elusive. In this study, we addressed these questions by characterizing the conformational heterogeneity of BamAB, BamACDE, and BamABCDE complexes in detergent micelles and/or Escherichia coli using pulsed dipolar electron spin resonance spectroscopy (PDS). We show that the binding of BamB does not induce any visible changes in BamA, and the BamAB complex exists in the IO conformation. The BamCDE complex induces an IO to LO transition through a coordinated movement along the BamA barrel. However, the extracellular loop 6 (L6) is unaffected by the presence of lipoproteins and exhibits large segmental dynamics extending to the exit pore. PDS experiments with the BamABCDE complex in intact E. coli confirmed the dynamic behavior of both the lateral gate and the L6 in the native environment. Our results demonstrate that the BamCDE complex plays a key role in the function by regulating lateral gating in BamA.
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Affiliation(s)
- Aathira Gopinath
- Department of Physics, Freie Universität Berlin, Berlin, 14195, Germany
- Institute of Biophysics, Goethe Universität Frankfurt, Frankfurt, 60438, Germany
| | - Tobias Rath
- Institute of Physical and Theoretical Chemistry, Goethe Universität Frankfurt, Frankfurt, 60438, Germany
| | - Nina Morgner
- Institute of Physical and Theoretical Chemistry, Goethe Universität Frankfurt, Frankfurt, 60438, Germany
| | - Benesh Joseph
- Department of Physics, Freie Universität Berlin, Berlin, 14195, Germany
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5
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Storek KM, Sun D, Rutherford ST. Inhibitors targeting BamA in gram-negative bacteria. BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH 2024; 1871:119609. [PMID: 37852326 DOI: 10.1016/j.bbamcr.2023.119609] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2022] [Revised: 06/08/2023] [Accepted: 09/19/2023] [Indexed: 10/20/2023]
Abstract
Antibiotic resistance has led to an increase in the number of patient hospitalizations and deaths. The situation for gram-negative bacteria is especially dire as the last new class of antibiotics active against these bacteria was introduced to the clinic over 60 years ago, thus there is an immediate unmet need for new antibiotic classes able to overcome resistance. The outer membrane, a unique and essential structure in gram-negative bacteria, contains multiple potential antibacterial targets including BamA, an outer membrane protein that folds and inserts transmembrane β-barrel proteins. BamA is essential and conserved, and its outer membrane location eliminates a barrier that molecules must overcome to access this target. Recently, antibacterial small molecules, natural products, peptides, and antibodies that inhibit BamA activity have been reported, validating the druggability of this target and generating potential leads for antibiotic development. This review will describe these BamA inhibitors, highlight their key attributes, and identify challenges with this potential target.
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Affiliation(s)
- Kelly M Storek
- Department of Infectious Diseases, Genentech Inc., South San Francisco, CA, USA
| | - Dawei Sun
- Department of Structural Biology, Genentech Inc., South San Francisco, CA, USA
| | - Steven T Rutherford
- Department of Infectious Diseases, Genentech Inc., South San Francisco, CA, USA.
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6
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Kuo K, Liu J, Pavlova A, Gumbart JC. Drug Binding to BamA Targets Its Lateral Gate. J Phys Chem B 2023; 127:7509-7517. [PMID: 37587651 PMCID: PMC10476194 DOI: 10.1021/acs.jpcb.3c04501] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2023] [Revised: 07/30/2023] [Indexed: 08/18/2023]
Abstract
BamA, the core component of the β-barrel assembly machinery (BAM) complex, is an outer-membrane protein (OMP) in Gram-negative bacteria. Its function is to insert and fold substrate OMPs into the outer membrane (OM). Evidence suggests that BamA follows the asymmetric hybrid-barrel model where the first and last strands of BamA separate, a process known as lateral gate opening, to allow nascent substrate OMP β-strands to sequentially insert and fold through β-augmentation. Recently, multiple lead compounds that interfere with BamA's function have been identified. We modeled and then docked one of these compounds into either the extracellular loops of BamA or the open lateral gate. With the compound docked in the loops, we found that the lateral gate remains closed during 5 μs molecular dynamics simulations. The same compound when docked in the open lateral gate stays bound to the β16 strand of BamA during the simulation, which would prevent substrate OMP folding. In addition, we simulated mutants of BamA that are resistant to one or more of the identified lead compounds. In these simulations, we observed a differing degree and/or frequency of opening of BamA's lateral gate compared to BamA-apo, suggesting that the mutations grant resistance by altering the dynamics at the gate. We conclude that the compounds act by inhibiting BamA lateral gate opening and/or binding of substrate, thus preventing subsequent OMP folding and insertion.
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Affiliation(s)
- Katie
M. Kuo
- School
of Chemistry and Biochemistry, Georgia Institute
of Technology, Atlanta, Georgia 30332, United States
| | - Jinchan Liu
- Department
of Molecular Biophysics and Biochemistry (MB&B), Yale University, New Haven, Connecticut 06510, United States
| | - Anna Pavlova
- School
of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - James C. Gumbart
- School
of Chemistry and Biochemistry, Georgia Institute
of Technology, Atlanta, Georgia 30332, United States
- School
of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
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7
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Haysom SF, Machin J, Whitehouse JM, Horne JE, Fenn K, Ma Y, El Mkami H, Böhringer N, Schäberle TF, Ranson NA, Radford SE, Pliotas C. Darobactin B Stabilises a Lateral-Closed Conformation of the BAM Complex in E. coli Cells. ANGEWANDTE CHEMIE (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2023; 135:e202218783. [PMID: 38515502 PMCID: PMC10952338 DOI: 10.1002/ange.202218783] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Indexed: 03/23/2024]
Abstract
The β-barrel assembly machinery (BAM complex) is essential for outer membrane protein (OMP) folding in Gram-negative bacteria, and represents a promising antimicrobial target. Several conformational states of BAM have been reported, but all have been obtained under conditions which lack the unique features and complexity of the outer membrane (OM). Here, we use Pulsed Electron-Electron Double Resonance (PELDOR, or DEER) spectroscopy distance measurements to interrogate the conformational ensemble of the BAM complex in E. coli cells. We show that BAM adopts a broad ensemble of conformations in the OM, while in the presence of the antibiotic darobactin B (DAR-B), BAM's conformational equilibrium shifts to a restricted ensemble consistent with the lateral closed state. Our in-cell PELDOR findings are supported by new cryoEM structures of BAM in the presence and absence of DAR-B. This work demonstrates the utility of PELDOR to map conformational changes in BAM within its native cellular environment.
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Affiliation(s)
- Samuel F. Haysom
- Astbury Centre for Structural Molecular BiologySchool of Molecular and Cellular BiologyUniversity of LeedsLeedsLS2 9JTUK
| | - Jonathan Machin
- Astbury Centre for Structural Molecular BiologySchool of Molecular and Cellular BiologyUniversity of LeedsLeedsLS2 9JTUK
| | - James M. Whitehouse
- Astbury Centre for Structural Molecular BiologySchool of Molecular and Cellular BiologyUniversity of LeedsLeedsLS2 9JTUK
| | - Jim E. Horne
- Astbury Centre for Structural Molecular BiologySchool of Molecular and Cellular BiologyUniversity of LeedsLeedsLS2 9JTUK
| | - Katherine Fenn
- Astbury Centre for Structural Molecular BiologySchool of Molecular and Cellular BiologyUniversity of LeedsLeedsLS2 9JTUK
| | - Yue Ma
- Astbury Centre for Structural Molecular BiologySchool of Biomedical SciencesUniversity of LeedsLeedsLS2 9JTUK
- School of Biological Sciences, Faculty of Biology, Medicine and HealthManchester Academic and Health Science CentreThe University of ManchesterManchesterM13 9PTUK
- Manchester Institute of BiotechnologyThe University of ManchesterManchesterM1 7DNUK
| | - Hassane El Mkami
- School of Physics and AstronomyUniversity of St. AndrewsSt. AndrewsKY16 9SSUK
| | - Nils Böhringer
- Institute for Insect BiotechnologyNatural Product ResearchJustus-Liebig-University GiessenOhlebergsweg 1235392GiessenGermany
- German Center for Infection Research (DZIF)Partner Site Giessen-Marburg-LangenOhlebergsweg 1235392GiessenGermany
| | - Till F. Schäberle
- Institute for Insect BiotechnologyNatural Product ResearchJustus-Liebig-University GiessenOhlebergsweg 1235392GiessenGermany
- German Center for Infection Research (DZIF)Partner Site Giessen-Marburg-LangenOhlebergsweg 1235392GiessenGermany
- Natural Product DepartmentFraunhofer-Institute for Molecular Biology and Applied Ecology (IME)Ohlebergsweg 1235392GiessenGermany
| | - Neil A. Ranson
- Astbury Centre for Structural Molecular BiologySchool of Molecular and Cellular BiologyUniversity of LeedsLeedsLS2 9JTUK
| | - Sheena E. Radford
- Astbury Centre for Structural Molecular BiologySchool of Molecular and Cellular BiologyUniversity of LeedsLeedsLS2 9JTUK
| | - Christos Pliotas
- Astbury Centre for Structural Molecular BiologySchool of Biomedical SciencesUniversity of LeedsLeedsLS2 9JTUK
- School of Biological Sciences, Faculty of Biology, Medicine and HealthManchester Academic and Health Science CentreThe University of ManchesterManchesterM13 9PTUK
- Manchester Institute of BiotechnologyThe University of ManchesterManchesterM1 7DNUK
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8
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Haysom SF, Machin J, Whitehouse JM, Horne JE, Fenn K, Ma Y, El Mkami H, Böhringer N, Schäberle TF, Ranson NA, Radford SE, Pliotas C. Darobactin B Stabilises a Lateral-Closed Conformation of the BAM Complex in E. coli Cells. Angew Chem Int Ed Engl 2023; 62:e202218783. [PMID: 37162386 PMCID: PMC10952311 DOI: 10.1002/anie.202218783] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Revised: 04/26/2023] [Accepted: 05/09/2023] [Indexed: 05/11/2023]
Abstract
The β-barrel assembly machinery (BAM complex) is essential for outer membrane protein (OMP) folding in Gram-negative bacteria, and represents a promising antimicrobial target. Several conformational states of BAM have been reported, but all have been obtained under conditions which lack the unique features and complexity of the outer membrane (OM). Here, we use Pulsed Electron-Electron Double Resonance (PELDOR, or DEER) spectroscopy distance measurements to interrogate the conformational ensemble of the BAM complex in E. coli cells. We show that BAM adopts a broad ensemble of conformations in the OM, while in the presence of the antibiotic darobactin B (DAR-B), BAM's conformational equilibrium shifts to a restricted ensemble consistent with the lateral closed state. Our in-cell PELDOR findings are supported by new cryoEM structures of BAM in the presence and absence of DAR-B. This work demonstrates the utility of PELDOR to map conformational changes in BAM within its native cellular environment.
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Affiliation(s)
- Samuel F. Haysom
- Astbury Centre for Structural Molecular BiologySchool of Molecular and Cellular BiologyUniversity of LeedsLeedsLS2 9JTUK
| | - Jonathan Machin
- Astbury Centre for Structural Molecular BiologySchool of Molecular and Cellular BiologyUniversity of LeedsLeedsLS2 9JTUK
| | - James M. Whitehouse
- Astbury Centre for Structural Molecular BiologySchool of Molecular and Cellular BiologyUniversity of LeedsLeedsLS2 9JTUK
| | - Jim E. Horne
- Astbury Centre for Structural Molecular BiologySchool of Molecular and Cellular BiologyUniversity of LeedsLeedsLS2 9JTUK
| | - Katherine Fenn
- Astbury Centre for Structural Molecular BiologySchool of Molecular and Cellular BiologyUniversity of LeedsLeedsLS2 9JTUK
| | - Yue Ma
- Astbury Centre for Structural Molecular BiologySchool of Biomedical SciencesUniversity of LeedsLeedsLS2 9JTUK
- School of Biological Sciences, Faculty of Biology, Medicine and HealthManchester Academic and Health Science CentreThe University of ManchesterManchesterM13 9PTUK
- Manchester Institute of BiotechnologyThe University of ManchesterManchesterM1 7DNUK
| | - Hassane El Mkami
- School of Physics and AstronomyUniversity of St. AndrewsSt. AndrewsKY16 9SSUK
| | - Nils Böhringer
- Institute for Insect BiotechnologyNatural Product ResearchJustus-Liebig-University GiessenOhlebergsweg 1235392GiessenGermany
- German Center for Infection Research (DZIF)Partner Site Giessen-Marburg-LangenOhlebergsweg 1235392GiessenGermany
| | - Till F. Schäberle
- Institute for Insect BiotechnologyNatural Product ResearchJustus-Liebig-University GiessenOhlebergsweg 1235392GiessenGermany
- German Center for Infection Research (DZIF)Partner Site Giessen-Marburg-LangenOhlebergsweg 1235392GiessenGermany
- Natural Product DepartmentFraunhofer-Institute for Molecular Biology and Applied Ecology (IME)Ohlebergsweg 1235392GiessenGermany
| | - Neil A. Ranson
- Astbury Centre for Structural Molecular BiologySchool of Molecular and Cellular BiologyUniversity of LeedsLeedsLS2 9JTUK
| | - Sheena E. Radford
- Astbury Centre for Structural Molecular BiologySchool of Molecular and Cellular BiologyUniversity of LeedsLeedsLS2 9JTUK
| | - Christos Pliotas
- Astbury Centre for Structural Molecular BiologySchool of Biomedical SciencesUniversity of LeedsLeedsLS2 9JTUK
- School of Biological Sciences, Faculty of Biology, Medicine and HealthManchester Academic and Health Science CentreThe University of ManchesterManchesterM13 9PTUK
- Manchester Institute of BiotechnologyThe University of ManchesterManchesterM1 7DNUK
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9
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Selvam R, Lim IHY, Lewis JC, Lim CH, Yap MKK, Tan HS. Selecting antibacterial aptamers against the BamA protein in Pseudomonas aeruginosa by incorporating genetic algorithm to optimise computational screening method. Sci Rep 2023; 13:7582. [PMID: 37164985 PMCID: PMC10170454 DOI: 10.1038/s41598-023-34643-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2023] [Accepted: 05/04/2023] [Indexed: 05/12/2023] Open
Abstract
Antibiotic resistance is one of the biggest threats to global health resulting in an increasing number of people suffering from severe illnesses or dying due to infections that were once easily curable with antibiotics. Pseudomonas aeruginosa is a major pathogen that has rapidly developed antibiotic resistance and WHO has categorised this pathogen under the critical list. DNA aptamers can act as a potential candidate for novel antimicrobial agents. In this study, we demonstrated that an existing aptamer is able to affect the growth of P. aeruginosa. A computational screen for aptamers that could bind to a well-conserved and essential outer membrane protein, BamA in Gram-negative bacteria was conducted. Molecular docking of about 100 functional DNA aptamers with BamA protein was performed via both local and global docking approaches. Additionally, genetic algorithm analysis was carried out to rank the aptamers based on their binding affinity. The top hits of aptamers with good binding to BamA protein were synthesised to investigate their in vitro antibacterial activity. Among all aptamers, Apt31, which is known to bind to an antitumor, Daunomycin, exhibited the highest HADDOCK score and resulted in a significant (p < 0.05) reduction in P. aeruginosa growth. Apt31 also induced membrane disruption that resulted in DNA leakage. Hence, computational screening may result in the identification of aptamers that bind to the desired active site with high affinity.
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Affiliation(s)
- Rupany Selvam
- School of Science, Monash University Malaysia, Bandar Sunway, Selangor, Malaysia
| | - Ian Han Yan Lim
- School of Science, Monash University Malaysia, Bandar Sunway, Selangor, Malaysia
| | | | - Chern Hong Lim
- School of Information Technology, Monash University Malaysia, Bandar Sunway, Selangor, Malaysia
| | | | - Hock Siew Tan
- School of Science, Monash University Malaysia, Bandar Sunway, Selangor, Malaysia.
- Tropical Medicine and Biology Multidisciplinary Platform, Monash University Malaysia, Bandar Sunway, Malaysia.
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10
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Xu Q, Guo M, Yu F. β-Barrel Assembly Machinery (BAM) Complex as Novel Antibacterial Drug Target. Molecules 2023; 28:molecules28093758. [PMID: 37175168 PMCID: PMC10180388 DOI: 10.3390/molecules28093758] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Revised: 03/05/2023] [Accepted: 03/08/2023] [Indexed: 05/15/2023] Open
Abstract
The outer membrane of Gram-negative bacteria is closely related to the pathogenicity and drug resistance of bacteria. Outer membrane proteins (OMPs) are a class of proteins with important biological functions on the outer membrane. The β-barrel assembly machinery (BAM) complex plays a key role in OMP biogenesis, which ensures that the OMP is inserted into the outer membrane in a correct folding manner and performs nutrient uptake, antibiotic resistance, cell adhesion, cell signaling, and maintenance of membrane stability and other functions. The BAM complex is highly conserved among Gram-negative bacteria. The abnormality of the BAM complex will lead to the obstruction of OMP folding, affect the function of the outer membrane, and eventually lead to bacterial death. In view of the important role of the BAM complex in OMP biogenesis, the BAM complex has become an attractive target for the development of new antibacterial drugs against Gram-negative bacteria. Here, we summarize the structure and function of the BAM complex and review the latest research progress of antibacterial drugs targeting BAM in order to provide a new perspective for the development of antibiotics.
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Affiliation(s)
- Qian Xu
- Laboratory of Molecular Pathology, Department of Pathology, Provincial Key Laboratory of Infectious Diseases and Molecular Immunopathology, Shantou University Medical College, Shantou 515041, China
| | - Min Guo
- Allergy Clinic, Zibo Central Hospital, Zibo 255000, China
| | - Feiyuan Yu
- Department of Cell Biology and Genetics, Shantou University Medical College, Shantou 515041, China
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11
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Overly Cottom C, Stephenson R, Wilson L, Noinaj N. Targeting BAM for Novel Therapeutics against Pathogenic Gram-Negative Bacteria. Antibiotics (Basel) 2023; 12:679. [PMID: 37107041 PMCID: PMC10135246 DOI: 10.3390/antibiotics12040679] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Revised: 02/28/2023] [Accepted: 03/06/2023] [Indexed: 04/29/2023] Open
Abstract
The growing emergence of multidrug resistance in bacterial pathogens is an immediate threat to human health worldwide. Unfortunately, there has not been a matching increase in the discovery of new antibiotics to combat this alarming trend. Novel contemporary approaches aimed at antibiotic discovery against Gram-negative bacterial pathogens have expanded focus to also include essential surface-exposed receptors and protein complexes, which have classically been targeted for vaccine development. One surface-exposed protein complex that has gained recent attention is the β-barrel assembly machinery (BAM), which is conserved and essential across all Gram-negative bacteria. BAM is responsible for the biogenesis of β-barrel outer membrane proteins (β-OMPs) into the outer membrane. These β-OMPs serve essential roles for the cell including nutrient uptake, signaling, and adhesion, but can also serve as virulence factors mediating pathogenesis. The mechanism for how BAM mediates β-OMP biogenesis is known to be dynamic and complex, offering multiple modes for inhibition by small molecules and targeting by larger biologics. In this review, we introduce BAM and establish why it is a promising and exciting new therapeutic target and present recent studies reporting novel compounds and vaccines targeting BAM across various bacteria. These reports have fueled ongoing and future research on BAM and have boosted interest in BAM for its therapeutic promise in combatting multidrug resistance in Gram-negative bacterial pathogens.
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Affiliation(s)
- Claire Overly Cottom
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA
| | - Robert Stephenson
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA
| | - Lindsey Wilson
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA
| | - Nicholas Noinaj
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA
- Markey Center for Structural Biology, Purdue University, West Lafayette, IN 47907, USA
- Purdue Institute of Inflammation, Immunology and Infectious Disease, Purdue University, West Lafayette, IN 47907, USA
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12
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Guest RL, Silhavy TJ. Cracking outer membrane biogenesis. BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH 2023; 1870:119405. [PMID: 36455781 PMCID: PMC9878550 DOI: 10.1016/j.bbamcr.2022.119405] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Revised: 10/25/2022] [Accepted: 11/07/2022] [Indexed: 11/30/2022]
Abstract
The outer membrane is a distinguishing feature of the Gram-negative envelope. It lies on the external face of the peptidoglycan sacculus and forms a robust permeability barrier that protects extracytoplasmic structures from environmental insults. Overcoming the barrier imposed by the outer membrane presents a significant hurdle towards developing novel antibiotics that are effective against Gram-negative bacteria. As the outer membrane is an essential component of the cell, proteins involved in its biogenesis are themselves promising antibiotic targets. Here, we summarize key findings that have built our understanding of the outer membrane. Foundational studies describing the discovery and composition of the outer membrane as well as the pathways involved in its construction are discussed.
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Affiliation(s)
- Randi L Guest
- Department of Molecular Biology, Princeton University, Lewis Thomas Laboratory, Washington Road, Princeton, NJ, 08544, United States of America
| | - Thomas J Silhavy
- Department of Molecular Biology, Princeton University, Lewis Thomas Laboratory, Washington Road, Princeton, NJ, 08544, United States of America.
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13
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Di Somma A, Cané C, Moretta A, Illiano A, Pinto G, Cavasso D, Amoresano A, Paduano L, Duilio A. The antimicrobial peptide Magainin-2 interacts with BamA impairing folding of E. coli membrane proteins. Front Chem 2022; 10:1013788. [PMID: 36324521 PMCID: PMC9620421 DOI: 10.3389/fchem.2022.1013788] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2022] [Accepted: 10/05/2022] [Indexed: 07/30/2023] Open
Abstract
Antimicrobial peptides (AMPs) are a unique and diverse group of molecules endowed with a broad spectrum of antibiotics properties that are being considered as new alternative therapeutic agents. Most of these peptides are membrane-active molecules, killing bacteria by membrane disruption. However, recently an increasing number of AMPs was shown to enter bacterial cells and target intracellular processes fundamental for bacterial life. In this paper we investigated the mechanism of action of Maganin-2 (Mag-2), a well-known antimicrobial peptide isolated from the African clawed frog Xenopus laevis, by functional proteomic approaches. Several proteins belonging to E. coli macromolecular membrane complexes were identified as Mag-2 putative interactors. Among these, we focused our attention on BamA a membrane protein belonging to the BAM complex responsible for the folding and insertion of nascent β-barrel Outer Membrane Proteins (OMPs) in the outer membrane. In silico predictions by molecular modelling, in vitro fluorescence binding and Light Scattering experiments carried out using a recombinant form of BamA confirmed the formation of a stable Mag-2/BamA complex and indicated a high affinity of the peptide for BamA. Functional implications of this interactions were investigated by two alternative and complementary approaches. The amount of outer membrane proteins OmpA and OmpF produced in E. coli following Mag-2 incubation were evaluated by both western blot analysis and quantitative tandem mass spectrometry in Multiple Reaction Monitoring scan mode. In both experiments a gradual decrease in outer membrane proteins production with time was observed as a consequence of Mag-2 treatment. These results suggested BamA as a possible good target for the rational design of new antibiotics since this protein is responsible for a crucial biological event of bacterial life and is absent in humans.
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Affiliation(s)
- Angela Di Somma
- Department of Chemical Sciences, University of Naples “Federico II”, Naples, Italy
- National Institute of Biostructures and Biosystems (INBB), Rome, Italy
| | - Carolina Cané
- Department of Chemical Sciences, University of Naples “Federico II”, Naples, Italy
| | - Antonio Moretta
- Institut NeuroMyoGène, Unité Physiopathologie et Génétique du Neurone et du Muscle, CNRS UMR5261, INSERM U1315, Université Claude Bernard Lyon 1, Lyon, France
| | - Anna Illiano
- Department of Chemical Sciences, University of Naples “Federico II”, Naples, Italy
- National Institute of Biostructures and Biosystems (INBB), Rome, Italy
| | - Gabriella Pinto
- Department of Chemical Sciences, University of Naples “Federico II”, Naples, Italy
- National Institute of Biostructures and Biosystems (INBB), Rome, Italy
| | - Domenico Cavasso
- Department of Chemical Sciences, University of Naples “Federico II”, Naples, Italy
| | - Angela Amoresano
- Department of Chemical Sciences, University of Naples “Federico II”, Naples, Italy
- National Institute of Biostructures and Biosystems (INBB), Rome, Italy
| | - Luigi Paduano
- Department of Chemical Sciences, University of Naples “Federico II”, Naples, Italy
| | - Angela Duilio
- Department of Chemical Sciences, University of Naples “Federico II”, Naples, Italy
- National Institute of Biostructures and Biosystems (INBB), Rome, Italy
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14
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Ongpipattanakul C, Desormeaux EK, DiCaprio A, van der Donk WA, Mitchell DA, Nair SK. Mechanism of Action of Ribosomally Synthesized and Post-Translationally Modified Peptides. Chem Rev 2022; 122:14722-14814. [PMID: 36049139 PMCID: PMC9897510 DOI: 10.1021/acs.chemrev.2c00210] [Citation(s) in RCA: 55] [Impact Index Per Article: 27.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Ribosomally synthesized and post-translationally modified peptides (RiPPs) are a natural product class that has undergone significant expansion due to the rapid growth in genome sequencing data and recognition that they are made by biosynthetic pathways that share many characteristic features. Their mode of actions cover a wide range of biological processes and include binding to membranes, receptors, enzymes, lipids, RNA, and metals as well as use as cofactors and signaling molecules. This review covers the currently known modes of action (MOA) of RiPPs. In turn, the mechanisms by which these molecules interact with their natural targets provide a rich set of molecular paradigms that can be used for the design or evolution of new or improved activities given the relative ease of engineering RiPPs. In this review, coverage is limited to RiPPs originating from bacteria.
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Affiliation(s)
- Chayanid Ongpipattanakul
- Department of Biochemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA
| | - Emily K. Desormeaux
- Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA
| | - Adam DiCaprio
- Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA
| | - Wilfred A. van der Donk
- Department of Biochemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA.,Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA.,Department of Howard Hughes Medical Institute, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA.,Departments of Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, 1206 West Gregory Drive, Urbana, Illinois 61801, USA.,Corresponding authors Wilfred A. van der Donk, , 217-244-5360, Douglas A. Mitchell, , 217-333-1345, Satish K. Nair, , 217-333-0641
| | - Douglas A. Mitchell
- Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA.,Department of Microbiology, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA.,Departments of Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, 1206 West Gregory Drive, Urbana, Illinois 61801, USA.,Corresponding authors Wilfred A. van der Donk, , 217-244-5360, Douglas A. Mitchell, , 217-333-1345, Satish K. Nair, , 217-333-0641
| | - Satish K. Nair
- Department of Biochemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA.,Departments of Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, 1206 West Gregory Drive, Urbana, Illinois 61801, USA.,Corresponding authors Wilfred A. van der Donk, , 217-244-5360, Douglas A. Mitchell, , 217-333-1345, Satish K. Nair, , 217-333-0641
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15
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Abstract
Several antibacterial compounds have recently been discovered that potentially inhibit the activity of BamA, an essential subunit of a heterooligomer (the barrel assembly machinery or BAM) that assembles outer membrane proteins (OMPs) in Gram-negative bacteria, but their mode of action is unclear. To address this issue, we examined the effect of three inhibitors on the biogenesis of a model E. coli OMP (EspP) in vivo. We found that darobactin potently inhibited the interaction of a conserved C-terminal sequence motif (the “β signal”) with BamA, but had no effect on assembly if added at a postbinding stage. In contrast, Polyphor peptide 7 and MRL-494 inhibited both binding and at least one later step of assembly. Taken together with previous studies that analyzed the binding of darobactin and Polyphor peptide 7 to BamA in vitro, our results strongly suggest that the two compounds inhibit BAM function by distinct competitive and allosteric mechanisms. In addition to providing insights into the properties of the antibacterial compounds, our results also provide direct experimental evidence that supports a model in which the binding of the β signal to BamA initiates the membrane insertion of OMPs.
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16
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Kuo KM, Ryoo D, Lundquist K, Gumbart JC. Modeling intermediates of BamA folding an outer membrane protein. Biophys J 2022; 121:3242-3252. [PMID: 35927955 PMCID: PMC9463690 DOI: 10.1016/j.bpj.2022.07.027] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Revised: 07/03/2022] [Accepted: 07/21/2022] [Indexed: 11/16/2022] Open
Abstract
BamA, the core component of the β-barrel assembly machinery complex, is an integral outer-membrane protein (OMP) in Gram-negative bacteria that catalyzes the folding and insertion of OMPs. A key feature of BamA relevant to its function is a lateral gate between its first and last β-strands. Opening of this lateral gate is one of the first steps in the asymmetric-hybrid-barrel model of BamA function. In this study, multiple hybrid-barrel folding intermediates of BamA and a substrate OMP, EspP, were constructed and simulated to better understand the model's physical consequences. The hybrid-barrel intermediates consisted of the BamA β-barrel and its POTRA5 domain and either one, two, three, four, five, or six β-hairpins of EspP. The simulation results support an asymmetric-hybrid-barrel model in which the BamA N-terminal β-strand forms stronger interactions with the substrate OMP than the C-terminal β-strand. A consistent "B"-shaped conformation of the final folding intermediate was observed, and the shape of the substrate β-barrel within the hybrid matched the shape of the fully folded substrate. Upon further investigation, inward-facing glycines were found at sharp bends within the hybrid and fully folded β-barrels. Together, the data suggest an influence of sequence on shape of the substrate barrel throughout the OMP folding process and of the fully folded OMP.
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Affiliation(s)
- Katie M Kuo
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia
| | - David Ryoo
- Interdisciplinary Bioengineering Graduate Program, Georgia Institute of Technology, Atlanta, Georgia
| | - Karl Lundquist
- Department of Biological Sciences, Markey Center for Structural Biology, Purdue University, West Lafayette, Indiana
| | - James C Gumbart
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia; School of Physics, Georgia Institute of Technology, Atlanta, Georgia.
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17
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Delgado KN, Montezuma-Rusca JM, Orbe IC, Caimano MJ, La Vake CJ, Luthra A, Hennelly CM, Nindo FN, Meyer JW, Jones LD, Parr JB, Salazar JC, Moody MA, Radolf JD, Hawley KL. Extracellular Loops of the Treponema pallidum FadL Orthologs TP0856 and TP0858 Elicit IgG Antibodies and IgG +-Specific B-Cells in the Rabbit Model of Experimental Syphilis. mBio 2022; 13:e0163922. [PMID: 35862766 PMCID: PMC9426418 DOI: 10.1128/mbio.01639-22] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2022] [Accepted: 06/14/2022] [Indexed: 12/03/2022] Open
Abstract
The resurgence of syphilis in the new millennium has called attention to the importance of a vaccine for global containment strategies. Studies with immune rabbit serum (IRS) indicate that a syphilis vaccine should elicit antibodies (Abs) that promote opsonophagocytosis of treponemes by activated macrophages. The availability of three-dimensional models for Treponema pallidum's (Tp) repertoire of outer membrane proteins (OMPs) provides an architectural framework for identification of candidate vaccinogens with extracellular loops (ECLs) as the targets for protective Abs. Herein, we used Pyrococcus furiosus thioredoxin (PfTrx) as a scaffold to display Tp OMP ECLs to interrogate sera and peripheral blood mononuclear cells (PBMCs) from immune rabbits for ECL-specific Abs and B cells. We validated this approach using a PfTrx scaffold presenting ECL4 from BamA, a known opsonic target. Using scaffolds displaying ECLs of the FadL orthologs TP0856 and TP0858, we determined that ECL2 and ECL4 of both proteins are strongly antigenic. Comparison of ELISA and immunoblot results suggested that the PfTrx scaffolds present conformational and linear epitopes. We then used the FadL ECL2 and ECL4 PfTrx constructs as "hooks" to confirm the presence of ECL-specific B cells in PBMCs from immune rabbits. Our results pinpoint immunogenic ECLs of two newly discovered OMPs, while advancing the utility of the rabbit model for circumventing bottlenecks in vaccine development associated with large-scale production of folded OMPs. They also lay the groundwork for production of rabbit monoclonal Abs (MAbs) to characterize potentially protective ECL epitopes at the atomic level. IMPORTANCE Recent identification and structural modeling of Treponema pallidum's (Tp) repertoire of outer membrane proteins (OMPs) represent a critical breakthrough in the decades long quest for a syphilis vaccine. However, little is known about the antigenic nature of these β-barrel-forming OMPs and, more specifically, their surface exposed regions, the extracellular loops (ECLs). In this study, using Pyrococcus furiosus thioredoxin (PfTrx) as a scaffold to display Tp OMP ECLs, we interrogated immune rabbit sera and peripheral blood mononuclear cells for the presence of antibodies (Abs) and circulating rare antigen-specific B cells. Our results pinpoint immunogenic ECLs of two newly discovered OMPs, while advancing the utility of the rabbit model for surveying the entire Tp OMPeome for promising OMP vaccinogens. This work represents a major advancement toward characterizing potentially protective OMP ECLs and future vaccine studies. Additionally, this strategy could be applied to OMPs of nonspirochetal bacterial pathogens.
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Affiliation(s)
| | - Jairo M Montezuma-Rusca
- Department of Medicine, UConn Health, Farmington, Connecticut, USA
- Division of Infectious Diseases, UConn Health, Farmington, Connecticut, USA
- Department of Pediatrics, UConn Health, Farmington, Connecticut, USA
| | - Isabel C Orbe
- Department of Pediatrics, UConn Health, Farmington, Connecticut, USA
| | - Melissa J Caimano
- Department of Medicine, UConn Health, Farmington, Connecticut, USA
- Department of Pediatrics, UConn Health, Farmington, Connecticut, USA
- Department of Molecular Biology and Biophysics, UConn Health, Farmington, Connecticut, USA
| | - Carson J La Vake
- Department of Pediatrics, UConn Health, Farmington, Connecticut, USA
| | - Amit Luthra
- Department of Medicine, UConn Health, Farmington, Connecticut, USA
- Department of Molecular Biology and Biophysics, UConn Health, Farmington, Connecticut, USA
| | - Christopher M Hennelly
- Division of Infectious Diseases, Department of Medicine, and Institute for Global Health and Infectious Diseases, University of North Carolina, Chapel Hill, North Carolina, USA
| | - Fredrick N Nindo
- Division of Infectious Diseases, Department of Medicine, and Institute for Global Health and Infectious Diseases, University of North Carolina, Chapel Hill, North Carolina, USA
| | - Jacob W Meyer
- Duke Human Vaccine Institute, Durham, North Carolina, USA
| | | | - Jonathan B Parr
- Division of Infectious Diseases, Department of Medicine, and Institute for Global Health and Infectious Diseases, University of North Carolina, Chapel Hill, North Carolina, USA
| | - Juan C Salazar
- Department of Pediatrics, UConn Health, Farmington, Connecticut, USA
- Division of Infectious Diseases and Immunology, Connecticut Children's, Hartford, Connecticut, USA
- Department of Immunology, UConn Health, Farmington, Connecticut, USA
| | - M Anthony Moody
- Duke Human Vaccine Institute, Durham, North Carolina, USA
- Department of Pediatrics, Duke University Medical Center, Durham, North Carolina, USA
- Department of Immunology, Duke University Medical Center, Durham, North Carolina, USA
| | - Justin D Radolf
- Department of Medicine, UConn Health, Farmington, Connecticut, USA
- Department of Pediatrics, UConn Health, Farmington, Connecticut, USA
- Department of Molecular Biology and Biophysics, UConn Health, Farmington, Connecticut, USA
- Department of Immunology, UConn Health, Farmington, Connecticut, USA
- Department of Genetics and Genome Sciences, UConn Health, Farmington, Connecticut, USA
| | - Kelly L Hawley
- Department of Medicine, UConn Health, Farmington, Connecticut, USA
- Department of Pediatrics, UConn Health, Farmington, Connecticut, USA
- Division of Infectious Diseases and Immunology, Connecticut Children's, Hartford, Connecticut, USA
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18
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Sicoli G, Konijnenberg A, Guérin J, Hessmann S, Del Nero E, Hernandez-Alba O, Lecher S, Rouaut G, Müggenburg L, Vezin H, Cianférani S, Sobott F, Schneider R, Jacob-Dubuisson F. Large-Scale Conformational Changes of FhaC Provide Insights Into the Two-Partner Secretion Mechanism. Front Mol Biosci 2022; 9:950871. [PMID: 35936790 PMCID: PMC9355242 DOI: 10.3389/fmolb.2022.950871] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2022] [Accepted: 06/24/2022] [Indexed: 11/30/2022] Open
Abstract
The Two-Partner secretion pathway mediates protein transport across the outer membrane of Gram-negative bacteria. TpsB transporters belong to the Omp85 superfamily, whose members catalyze protein insertion into, or translocation across membranes without external energy sources. They are composed of a transmembrane β barrel preceded by two periplasmic POTRA domains that bind the incoming protein substrate. Here we used an integrative approach combining in vivo assays, mass spectrometry, nuclear magnetic resonance and electron paramagnetic resonance techniques suitable to detect minor states in heterogeneous populations, to explore transient conformers of the TpsB transporter FhaC. This revealed substantial, spontaneous conformational changes on a slow time scale, with parts of the POTRA2 domain approaching the lipid bilayer and the protein’s surface loops. Specifically, our data indicate that an amphipathic POTRA2 β hairpin can insert into the β barrel. We propose that these motions enlarge the channel and initiate substrate secretion. Our data propose a solution to the conundrum how TpsB transporters mediate protein secretion without the need for cofactors, by utilizing intrinsic protein dynamics.
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Affiliation(s)
- Giuseppe Sicoli
- Laboratoire Avancé de Spectroscopie pour les Interactions, la Réactivité et l’Environnement (LASIRE), UMR CNRS 8516, Université de Lille, Lille, France
| | | | - Jérémy Guérin
- CNRS, INSERM, Institut Pasteur de Lille, Université de Lille, U1019-UMR9017-CIIL-Center for Infection and Immunity of Lille, Lille, France
| | - Steve Hessmann
- Laboratoire de Spectrométrie de Masse BioOrganique, Université de Strasbourg, CNRS, Strasbourg, France
- Infrastructure Nationale de Protéomique ProFI – FR 2048, Strasbourg, France
| | - Elise Del Nero
- Laboratoire de Spectrométrie de Masse BioOrganique, Université de Strasbourg, CNRS, Strasbourg, France
- Infrastructure Nationale de Protéomique ProFI – FR 2048, Strasbourg, France
| | - Oscar Hernandez-Alba
- Laboratoire de Spectrométrie de Masse BioOrganique, Université de Strasbourg, CNRS, Strasbourg, France
- Infrastructure Nationale de Protéomique ProFI – FR 2048, Strasbourg, France
| | - Sophie Lecher
- CNRS, INSERM, Institut Pasteur de Lille, Université de Lille, U1019-UMR9017-CIIL-Center for Infection and Immunity of Lille, Lille, France
| | - Guillaume Rouaut
- CNRS EMR9002 Integrative Structural Biology, Lille, France
- INSERM, CHU Lille, U1167 - RID-AGE - Risk Factors and Molecular Determinants of Aging-Related Diseases, Institut Pasteur de Lille, Université de Lille, Lille, France
| | - Linn Müggenburg
- CNRS EMR9002 Integrative Structural Biology, Lille, France
- INSERM, CHU Lille, U1167 - RID-AGE - Risk Factors and Molecular Determinants of Aging-Related Diseases, Institut Pasteur de Lille, Université de Lille, Lille, France
| | - Hervé Vezin
- Laboratoire Avancé de Spectroscopie pour les Interactions, la Réactivité et l’Environnement (LASIRE), UMR CNRS 8516, Université de Lille, Lille, France
| | - Sarah Cianférani
- Laboratoire de Spectrométrie de Masse BioOrganique, Université de Strasbourg, CNRS, Strasbourg, France
- Infrastructure Nationale de Protéomique ProFI – FR 2048, Strasbourg, France
| | - Frank Sobott
- BAMS Research Group, University of Antwerp, Antwerp, Belgium
- Astbury Centre for Structural Molecular Biology and the School of Molecular and Cellular Biology, University of Leeds, Leeds, United Kingdom
| | - Robert Schneider
- CNRS EMR9002 Integrative Structural Biology, Lille, France
- INSERM, CHU Lille, U1167 - RID-AGE - Risk Factors and Molecular Determinants of Aging-Related Diseases, Institut Pasteur de Lille, Université de Lille, Lille, France
- *Correspondence: Robert Schneider, ; Françoise Jacob-Dubuisson,
| | - Françoise Jacob-Dubuisson
- CNRS, INSERM, Institut Pasteur de Lille, Université de Lille, U1019-UMR9017-CIIL-Center for Infection and Immunity of Lille, Lille, France
- *Correspondence: Robert Schneider, ; Françoise Jacob-Dubuisson,
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19
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Dynamic interplay between the periplasmic chaperone SurA and the BAM complex in outer membrane protein folding. Commun Biol 2022; 5:560. [PMID: 35676411 PMCID: PMC9177699 DOI: 10.1038/s42003-022-03502-w] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2022] [Accepted: 05/18/2022] [Indexed: 12/12/2022] Open
Abstract
Correct folding of outer membrane proteins (OMPs) into the outer membrane of Gram-negative bacteria depends on delivery of unfolded OMPs to the β-barrel assembly machinery (BAM). How unfolded substrates are presented to BAM remains elusive, but the major OMP chaperone SurA is proposed to play a key role. Here, we have used hydrogen deuterium exchange mass spectrometry (HDX-MS), crosslinking, in vitro folding and binding assays and computational modelling to show that the core domain of SurA and one of its two PPIase domains are key to the SurA-BAM interaction and are required for maximal catalysis of OMP folding. We reveal that binding causes changes in BAM and SurA conformation and/or dynamics distal to the sites of binding, including at the BamA β1-β16 seam. We propose a model for OMP biogenesis in which SurA plays a crucial role in OMP delivery and primes BAM to accept substrates for folding. Interaction of the outer membrane protein (OMP) chaperone SurA and the OMP folding catalyst BAM results in changes in the conformational ensembles of both species, suggesting a mechanism for delivery of OMPs to BAM in Gram-negative bacteria.
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20
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Doyle MT, Bernstein HD. Function of the Omp85 Superfamily of Outer Membrane Protein Assembly Factors and Polypeptide Transporters. Annu Rev Microbiol 2022; 76:259-279. [PMID: 35650668 DOI: 10.1146/annurev-micro-033021-023719] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The Omp85 protein superfamily is found in the outer membrane (OM) of all gram-negative bacteria and eukaryotic organelles of bacterial origin. Members of the family catalyze both the membrane insertion of β-barrel proteins and the translocation of proteins across the OM. Although the mechanism(s) by which these proteins function is unclear, striking new insights have emerged from recent biochemical and structural studies. In this review we discuss the entire Omp85 superfamily but focus on the function of the best-studied member, BamA, which is an essential and highly conserved component of the bacterial barrel assembly machinery (BAM). Because BamA has multiple functions that overlap with those of other Omp85 proteins, it is likely the prototypical member of the Omp85 superfamily. Furthermore, BamA has become a protein of great interest because of the recent discovery of small-molecule inhibitors that potentially represent an important new class of antibiotics. Expected final online publication date for the Annual Review of Microbiology, Volume 76 is September 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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Affiliation(s)
- Matthew Thomas Doyle
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, USA; ,
| | - Harris D Bernstein
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, USA; ,
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21
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Doyle MT, Jimah JR, Dowdy T, Ohlemacher SI, Larion M, Hinshaw JE, Bernstein HD. Cryo-EM structures reveal multiple stages of bacterial outer membrane protein folding. Cell 2022; 185:1143-1156.e13. [PMID: 35294859 DOI: 10.1016/j.cell.2022.02.016] [Citation(s) in RCA: 40] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2021] [Revised: 12/01/2021] [Accepted: 02/13/2022] [Indexed: 02/08/2023]
Abstract
Transmembrane β barrel proteins are folded into the outer membrane (OM) of Gram-negative bacteria by the β barrel assembly machinery (BAM) via a poorly understood process that occurs without known external energy sources. Here, we used single-particle cryo-EM to visualize the folding dynamics of a model β barrel protein (EspP) by BAM. We found that BAM binds the highly conserved "β signal" motif of EspP to correctly orient β strands in the OM during folding. We also found that the folding of EspP proceeds via "hybrid-barrel" intermediates in which membrane integrated β sheets are attached to the essential BAM subunit, BamA. The structures show an unprecedented deflection of the membrane surrounding the EspP intermediates and suggest that β sheets progressively fold toward BamA to form a β barrel. Along with in vivo experiments that tracked β barrel folding while the OM tension was modified, our results support a model in which BAM harnesses OM elasticity to accelerate β barrel folding.
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Affiliation(s)
- Matthew Thomas Doyle
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - John R Jimah
- Laboratory of Cell and Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Tyrone Dowdy
- Neuro-Oncology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Shannon I Ohlemacher
- Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Mioara Larion
- Neuro-Oncology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Jenny E Hinshaw
- Laboratory of Cell and Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
| | - Harris D Bernstein
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
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22
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Plasticity within the barrel domain of BamA mediates a hybrid-barrel mechanism by BAM. Nat Commun 2021; 12:7131. [PMID: 34880256 PMCID: PMC8655018 DOI: 10.1038/s41467-021-27449-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Accepted: 11/22/2021] [Indexed: 12/26/2022] Open
Abstract
In Gram-negative bacteria, the biogenesis of β-barrel outer membrane proteins is mediated by the β-barrel assembly machinery (BAM). The mechanism employed by BAM is complex and so far- incompletely understood. Here, we report the structures of BAM in nanodiscs, prepared using polar lipids and native membranes, where we observe an outward-open state. Mutations in the barrel domain of BamA reveal that plasticity in BAM is essential, particularly along the lateral seam of the barrel domain, which is further supported by molecular dynamics simulations that show conformational dynamics in BAM are modulated by the accessory proteins. We also report the structure of BAM in complex with EspP, which reveals an early folding intermediate where EspP threads from the underside of BAM and incorporates into the barrel domain of BamA, supporting a hybrid-barrel budding mechanism in which the substrate is folded into the membrane sequentially rather than as a single unit.
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23
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High-throughput suppressor screen demonstrates that RcsF monitors outer membrane integrity and not Bam complex function. Proc Natl Acad Sci U S A 2021; 118:2100369118. [PMID: 34349021 DOI: 10.1073/pnas.2100369118] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The regulator of capsule synthesis (Rcs) is a complex signaling cascade that monitors gram-negative cell envelope integrity. The outer membrane (OM) lipoprotein RcsF is the sensory component, but how RcsF functions remains elusive. RcsF interacts with the β-barrel assembly machinery (Bam) complex, which assembles RcsF in complex with OM proteins (OMPs), resulting in RcsF's partial cell surface exposure. Elucidating whether RcsF/Bam or RcsF/OMP interactions are important for its sensing function is challenging because the Bam complex is essential, and partial loss-of-function mutations broadly compromise the OM biogenesis. Our recent discovery that, in the absence of nonessential component BamE, RcsF inhibits function of the central component BamA provided a genetic tool to select mutations that specifically prevent RcsF/BamA interactions. We employed a high-throughput suppressor screen to isolate a collection of such rcsF and bamA mutants and characterized their impact on RcsF/OMP assembly and Rcs signaling. Using these mutants and BamA inhibitors MRL-494L and darobactin, we provide multiple lines of evidence against the model in which RcsF senses Bam complex function. We show that Rcs activation in bam mutants results from secondary OM and lipopolysaccharide defects and that RcsF/OMP assembly is required for this activation, supporting an active role of RcsF/OMP complexes in sensing OM stress.
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24
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Cai X, Liu L, Qiu C, Wen C, He Y, Cui Y, Li S, Zhang X, Zhang L, Tian C, Bi L, Zhou ZH, Gong W. Identification and architecture of a putative secretion tube across mycobacterial outer envelope. SCIENCE ADVANCES 2021; 7:7/34/eabg5656. [PMID: 34417177 PMCID: PMC8378821 DOI: 10.1126/sciadv.abg5656] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/16/2021] [Accepted: 06/29/2021] [Indexed: 06/13/2023]
Abstract
Tuberculosis-causing mycobacteria have thick cell-wall and capsule layers that are formed from complex structures. Protein secretion across these barriers depends on a specialized protein secretion system, but none has been reported. We show that Mycobacterium tuberculosis Rv3705c and its homologous MSMEG_6251 in Mycobacterium smegmatis are tube-forming proteins in the mycobacterial envelope (TiME). Crystallographic and cryo-EM structures of these two proteins show that both proteins form rotationally symmetric rings. Two layers of TiME rings pack together in a tail-to-tail manner into a ring-shaped complex, which, in turn, stacks together to form tubes. M. smegmatis TiME was detected mainly in the cell wall and capsule. Knocking out the TiME gene markedly decreased the amount of secreted protein in the M. smegmatis culture medium, and expression of this gene in knocked-out strain partially restored the level of secreted protein. Our structure and functional data thus suggest that TiME forms a protein transport tube across the mycobacterial outer envelope.
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Affiliation(s)
- Xiaoying Cai
- School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China
| | - Lei Liu
- Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui, China
| | - Chunhong Qiu
- School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China
| | - Chongzheng Wen
- Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui, China
| | - Yao He
- California NanoSystems Institute, University of California, Los Angeles (UCLA), Los Angeles, CA 90095, USA
- Department of Microbiology, Immunology and Molecular Genetics, UCLA, Los Angeles, CA 90095, USA
| | - Yanxiang Cui
- California NanoSystems Institute, University of California, Los Angeles (UCLA), Los Angeles, CA 90095, USA
| | - Siyu Li
- School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China
| | - Xuan Zhang
- Institute of Health Science, Institutes of Physical Science and Information Technology, Anhui University, Hefei, Anhui, China
| | - Longhua Zhang
- School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China
| | - Changlin Tian
- School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China
| | - Lijun Bi
- Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Z Hong Zhou
- California NanoSystems Institute, University of California, Los Angeles (UCLA), Los Angeles, CA 90095, USA.
- Department of Microbiology, Immunology and Molecular Genetics, UCLA, Los Angeles, CA 90095, USA
| | - Weimin Gong
- School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China.
- Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui, China
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25
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The role of membrane destabilisation and protein dynamics in BAM catalysed OMP folding. Nat Commun 2021; 12:4174. [PMID: 34234105 PMCID: PMC8263589 DOI: 10.1038/s41467-021-24432-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Accepted: 06/08/2021] [Indexed: 02/06/2023] Open
Abstract
The folding of β-barrel outer membrane proteins (OMPs) in Gram-negative bacteria is catalysed by the β-barrel assembly machinery (BAM). How lateral opening in the β-barrel of the major subunit BamA assists in OMP folding, and the contribution of membrane disruption to BAM catalysis remain unresolved. Here, we use an anti-BamA monoclonal antibody fragment (Fab1) and two disulphide-crosslinked BAM variants (lid-locked (LL), and POTRA-5-locked (P5L)) to dissect these roles. Despite being lethal in vivo, we show that all complexes catalyse folding in vitro, albeit less efficiently than wild-type BAM. CryoEM reveals that while Fab1 and BAM-P5L trap an open-barrel state, BAM-LL contains a mixture of closed and contorted, partially-open structures. Finally, all three complexes globally destabilise the lipid bilayer, while BamA does not, revealing that the BAM lipoproteins are required for this function. Together the results provide insights into the role of BAM structure and lipid dynamics in OMP folding.
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26
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CESA-LUNA CATHERINE, ALATORRE-CRUZ JULIAMARÍA, CARREÑO-LÓPEZ RICARDO, QUINTERO-HERNÁNDEZ VERÓNICA, BAEZ ANTONINO. Emerging Applications of Bacteriocins as Antimicrobials, Anticancer Drugs, and Modulators of The Gastrointestinal Microbiota. Pol J Microbiol 2021; 70:143-159. [PMID: 34349808 PMCID: PMC8326989 DOI: 10.33073/pjm-2021-020] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Revised: 04/06/2021] [Accepted: 04/25/2021] [Indexed: 02/06/2023] Open
Abstract
The use of bacteriocins holds great promise in different areas such as health, food, nutrition, veterinary, nanotechnology, among others. Many research groups worldwide continue to advance the knowledge to unravel a novel range of therapeutic agents and food preservatives. This review addresses the advances of bacteriocins and their producer organisms as biocontrol agents for applications in the medical industry and agriculture. Furthermore, the bacteriocin mechanism of action and structural characteristics will be reviewed. Finally, the potential role of bacteriocins to modulate the signaling in host-associated microbial communities will be discussed.
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Affiliation(s)
- CATHERINE CESA-LUNA
- Centro de Investigaciones en Ciencias Microbiológicas (CICM), Instituto de Ciencias (IC), Benemérita Universidad Autónoma de Puebla (BUAP), Puebla, México
| | | | - RICARDO CARREÑO-LÓPEZ
- Centro de Investigaciones en Ciencias Microbiológicas (CICM), Instituto de Ciencias (IC), Benemérita Universidad Autónoma de Puebla (BUAP), Puebla, México
| | | | - ANTONINO BAEZ
- Centro de Investigaciones en Ciencias Microbiológicas (CICM), Instituto de Ciencias (IC), Benemérita Universidad Autónoma de Puebla (BUAP), Puebla, México
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27
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Page JE, Walker S. Natural products that target the cell envelope. Curr Opin Microbiol 2021; 61:16-24. [PMID: 33662818 PMCID: PMC8169544 DOI: 10.1016/j.mib.2021.02.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2020] [Revised: 01/22/2021] [Accepted: 02/03/2021] [Indexed: 02/07/2023]
Abstract
The inexorable spread of resistance to clinically used drugs demands that we maintain a full pipeline of antibiotic candidates. As organisms have struggled to survive and compete over evolutionary history, they have developed the capacity to make a remarkably diverse array of natural products that target the cell envelope. A few have been developed for use in the clinic but most have not, and there are still an enormous number of opportunities to investigate. Substrate-binding antibiotics for Gram-positive organisms, phage-derived lysins, and outer membrane protein-targeting agents for Gram-negative organisms represent promising avenues where nature's gifts may be repurposed for use in the clinic.
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Affiliation(s)
- Julia E Page
- Department of Microbiology, Harvard Medical School, HIM1013, 4 Blackfan Circle, Boston, MA, 02115, United States
| | - Suzanne Walker
- Department of Microbiology, Harvard Medical School, HIM1013, 4 Blackfan Circle, Boston, MA, 02115, United States.
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28
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Steenhuis M, van Ulsen P, Martin NI, Luirink J. A ban on BAM: an update on inhibitors of the β-barrel assembly machinery. FEMS Microbiol Lett 2021; 368:6287571. [PMID: 34048543 DOI: 10.1093/femsle/fnab059] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Accepted: 05/26/2021] [Indexed: 12/15/2022] Open
Abstract
Gram-negative pathogens are a rapidly increasing threat to human health worldwide due to high rates of antibiotic resistance and the lack of development of novel antibiotics. The protective cell envelope of gram-negative bacteria is a major permeability barrier that contributes to the problem by restricting the uptake of antibiotics. On the other hand, its unique architecture also makes it a suitable target for antibiotic interference. In particular, essential multiprotein machines that are required for biogenesis of the outer membrane have attracted attention in antibacterial design strategies. Recently, significant progress has been made in the development of inhibitors of the β-barrel assembly machine (BAM) complex. Here, we summarize the current state of drug development efforts targeting the BAM complex in pursuit of new antibiotics.
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Affiliation(s)
- Maurice Steenhuis
- Department of Molecular Microbiology, Amsterdam Institute of Molecular and Life Sciences (AIMMS), Vrije Universiteit, De Boelelaan 1085, 1081 HV, Amsterdam, The Netherlands
| | - Peter van Ulsen
- Department of Molecular Microbiology, Amsterdam Institute of Molecular and Life Sciences (AIMMS), Vrije Universiteit, De Boelelaan 1085, 1081 HV, Amsterdam, The Netherlands
| | - Nathaniel I Martin
- Biological Chemistry Group, Institute of Biology Leiden, Leiden University, Nonnensteeg 3, 2311 VJ, Leiden, The Netherlands
| | - Joen Luirink
- Department of Molecular Microbiology, Amsterdam Institute of Molecular and Life Sciences (AIMMS), Vrije Universiteit, De Boelelaan 1085, 1081 HV, Amsterdam, The Netherlands
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29
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Schlick T, Portillo-Ledesma S, Myers CG, Beljak L, Chen J, Dakhel S, Darling D, Ghosh S, Hall J, Jan M, Liang E, Saju S, Vohr M, Wu C, Xu Y, Xue E. Biomolecular Modeling and Simulation: A Prospering Multidisciplinary Field. Annu Rev Biophys 2021; 50:267-301. [PMID: 33606945 PMCID: PMC8105287 DOI: 10.1146/annurev-biophys-091720-102019] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
We reassess progress in the field of biomolecular modeling and simulation, following up on our perspective published in 2011. By reviewing metrics for the field's productivity and providing examples of success, we underscore the productive phase of the field, whose short-term expectations were overestimated and long-term effects underestimated. Such successes include prediction of structures and mechanisms; generation of new insights into biomolecular activity; and thriving collaborations between modeling and experimentation, including experiments driven by modeling. We also discuss the impact of field exercises and web games on the field's progress. Overall, we note tremendous success by the biomolecular modeling community in utilization of computer power; improvement in force fields; and development and application of new algorithms, notably machine learning and artificial intelligence. The combined advances are enhancing the accuracy andscope of modeling and simulation, establishing an exemplary discipline where experiment and theory or simulations are full partners.
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Affiliation(s)
- Tamar Schlick
- Department of Chemistry, New York University, New York, New York 10003, USA;
- Courant Institute of Mathematical Sciences, New York University, New York, New York 10012, USA
- New York University-East China Normal University Center for Computational Chemistry, New York University Shanghai, Shanghai 200122, China
| | | | - Christopher G Myers
- Department of Chemistry, New York University, New York, New York 10003, USA;
| | - Lauren Beljak
- College of Arts and Science, New York University, New York, New York 10003, USA
| | - Justin Chen
- College of Arts and Science, New York University, New York, New York 10003, USA
| | - Sami Dakhel
- College of Arts and Science, New York University, New York, New York 10003, USA
| | - Daniel Darling
- College of Arts and Science, New York University, New York, New York 10003, USA
| | - Sayak Ghosh
- College of Arts and Science, New York University, New York, New York 10003, USA
| | - Joseph Hall
- College of Arts and Science, New York University, New York, New York 10003, USA
| | - Mikaeel Jan
- College of Arts and Science, New York University, New York, New York 10003, USA
| | - Emily Liang
- College of Arts and Science, New York University, New York, New York 10003, USA
| | - Sera Saju
- College of Arts and Science, New York University, New York, New York 10003, USA
| | - Mackenzie Vohr
- College of Arts and Science, New York University, New York, New York 10003, USA
| | - Chris Wu
- College of Arts and Science, New York University, New York, New York 10003, USA
| | - Yifan Xu
- College of Arts and Science, New York University, New York, New York 10003, USA
| | - Eva Xue
- College of Arts and Science, New York University, New York, New York 10003, USA
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30
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Wang X, Peterson JH, Bernstein HD. Bacterial Outer Membrane Proteins Are Targeted to the Bam Complex by Two Parallel Mechanisms. mBio 2021; 12:e00597-21. [PMID: 33947759 PMCID: PMC8262991 DOI: 10.1128/mbio.00597-21] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2021] [Accepted: 03/12/2021] [Indexed: 01/23/2023] Open
Abstract
Membrane proteins that are integrated into the outer membrane of Gram-negative bacteria typically contain a unique "β barrel" structure that serves as a membrane spanning segment. A conserved "β signal" motif is located at the C terminus of the β barrel of many outer membrane proteins (OMPs), but the function of this sequence is unclear. We found that mutations in the β signal slightly delayed the assembly of three model Escherichia coli OMPs by reducing their affinity for the barrel assembly machinery (Bam) complex, a heterooligomer that catalyzes β barrel insertion, and led to the degradation of a fraction of the protein in the periplasm. Interestingly, the absence of the periplasmic chaperone SurA amplified the effect of the mutations and caused the complete degradation of the mutant proteins. In contrast, the absence of another periplasmic chaperone (Skp) suppressed the effect of the mutations and considerably enhanced the efficiency of assembly. Our results reveal the existence of two parallel OMP targeting mechanisms that rely on a cis-acting peptide (the β signal) and a trans-acting factor (SurA), respectively. Our results also challenge the long-standing view that periplasmic chaperones are redundant and provide evidence that they have specialized functions.IMPORTANCE Proteins that are embedded in the outer membrane of Gram-negative bacteria (OMPs) play an important role in protecting the cell from harmful chemicals. OMPs share a common architecture and often contain a conserved sequence motif (β motif) of unknown function. Although OMPs are escorted to the outer membrane by proteins called chaperones, the exact function of the chaperones is also unclear. Here, we show that the β motif and the chaperone SurA both target OMPs to the β barrel insertion machinery in the outer membrane. In contrast, the chaperone Skp delivers unintegrated OMPs to protein degradation complexes. Our results challenge the long-standing view that chaperones are functionally redundant and strongly suggest that they have specialized roles in OMP targeting and quality control.
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Affiliation(s)
- Xu Wang
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Janine H Peterson
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Harris D Bernstein
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, USA
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31
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Doyle MT, Bernstein HD. BamA forms a translocation channel for polypeptide export across the bacterial outer membrane. Mol Cell 2021; 81:2000-2012.e3. [PMID: 33705710 DOI: 10.1016/j.molcel.2021.02.023] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Revised: 01/05/2021] [Accepted: 02/18/2021] [Indexed: 12/18/2022]
Abstract
The β-barrel assembly machine (BAM) integrates β-barrel proteins into the outer membrane (OM) of Gram-negative bacteria. An essential BAM subunit (BamA) catalyzes integration by promoting the formation of a hybrid-barrel intermediate state between its own β-barrel domain and that of its client proteins. Here we show that in addition to catalyzing the integration of β-barrel proteins, BamA functions as a polypeptide export channel. In vivo structural mapping via intermolecular disulfide crosslinking showed that the extracellular "passenger" domain of a member of the "autotransporter" superfamily of virulence factors traverses the OM through the BamA β-barrel lumen. Furthermore, we demonstrate that a highly conserved residue within autotransporter β-barrels is required to position the passenger inside BamA to initiate translocation and that during translocation, the passenger stabilizes the hybrid-barrel state. Our results not only establish a new function for BamA but also unify the divergent functions of BamA and other "Omp85" superfamily transporters.
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Affiliation(s)
- Matthew Thomas Doyle
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Harris David Bernstein
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
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32
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Diederichs KA, Buchanan SK, Botos I. Building Better Barrels - β-barrel Biogenesis and Insertion in Bacteria and Mitochondria. J Mol Biol 2021; 433:166894. [PMID: 33639212 PMCID: PMC8292188 DOI: 10.1016/j.jmb.2021.166894] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2020] [Revised: 02/18/2021] [Accepted: 02/18/2021] [Indexed: 01/20/2023]
Abstract
β-barrel proteins are folded and inserted into outer membranes by multi-subunit protein complexes that are conserved across different types of outer membranes. In Gram-negative bacteria this complex is the barrel-assembly machinery (BAM), in mitochondria it is the sorting and assembly machinery (SAM) complex, and in chloroplasts it is the outer envelope protein Oep80. Mitochondrial β-barrel precursor proteins are translocated from the cytoplasm to the intermembrane space by the translocase of the outer membrane (TOM) complex, and stabilized by molecular chaperones before interaction with the assembly machinery. Outer membrane bacterial BamA interacts with four periplasmic accessory proteins, whereas mitochondrial Sam50 interacts with two cytoplasmic accessory proteins. Despite these major architectural differences between BAM and SAM complexes, their core proteins, BamA and Sam50, seem to function the same way. Based on the new SAM complex structures, we propose that the mitochondrial β-barrel folding mechanism follows the budding model with barrel-switching aiding in the release of new barrels. We also built a new molecular model for Tom22 interacting with Sam37 to identify regions that could mediate TOM-SAM supercomplex formation.
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Affiliation(s)
- Kathryn A Diederichs
- Laboratory of Molecular Biology, National Institute of Diabetes & Digestive & Kidney Diseases, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD 20892, USA
| | - Susan K Buchanan
- Laboratory of Molecular Biology, National Institute of Diabetes & Digestive & Kidney Diseases, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD 20892, USA
| | - Istvan Botos
- Laboratory of Molecular Biology, National Institute of Diabetes & Digestive & Kidney Diseases, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD 20892, USA.
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33
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Tomasek D, Kahne D. The assembly of β-barrel outer membrane proteins. Curr Opin Microbiol 2021; 60:16-23. [PMID: 33561734 DOI: 10.1016/j.mib.2021.01.009] [Citation(s) in RCA: 39] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Revised: 01/17/2021] [Accepted: 01/22/2021] [Indexed: 01/21/2023]
Abstract
The outer membranes of Gram-negative bacteria, mitochondria, and chloroplasts contain β-barrel integral membrane proteins. In bacteria, the five-protein β-barrel assembly machine (Bam) accelerates the folding and membrane integration of these proteins. The central component of the machine, BamA, contains a β-barrel domain that can adopt a lateral-open state with its N-terminal and C-terminal β-strands unpaired. Recently, strategies have been developed to capture β-barrel folding intermediates on the Bam complex. Biochemical and structural studies provide support for a model in which substrates assemble at the lateral opening of BamA. In this model, the N-terminal β-strand of BamA captures the C-terminal β-strand of substrates by hydrogen bonding to allow their directional folding and subsequent release into the membrane.
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Affiliation(s)
- David Tomasek
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA; Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA
| | - Daniel Kahne
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA; Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA; Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA.
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34
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Tiwari PB, Mahalakshmi R. Interplay of protein primary sequence, lipid membrane, and chaperone in β-barrel assembly. Protein Sci 2021; 30:624-637. [PMID: 33410567 DOI: 10.1002/pro.4022] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Revised: 12/25/2020] [Accepted: 12/30/2020] [Indexed: 02/06/2023]
Abstract
The outer membrane of a Gram-negative bacterium is a crucial barrier between the external environment and its internal physiology. This barrier is bridged selectively by β-barrel outer membrane proteins (OMPs). The in vivo folding and biogenesis of OMPs necessitates the assistance of the outer membrane chaperone BamA. Nevertheless, OMPs retain the ability of independent self-assembly in vitro. Hence, it is unclear whether substrate-chaperone dynamics is influenced by the intrinsic ability of OMPs to fold, the magnitude of BamA-OMP interdependence, and the contribution of BamA to the kinetics of OMP assembly. We addressed this by monitoring the assembly kinetics of multiple 8-stranded β-barrel OMP substrates with(out) BamA. We also examined whether BamA is species-specific, or nonspecifically accelerates folding kinetics of substrates from independent species. Our findings reveal BamA as a substrate-independent promiscuous molecular chaperone, which assists the unfolded OMP to overcome the kinetic barrier imposed by the bilayer membrane. We additionally show that while BamA kinetically accelerates OMP folding, the OMP primary sequence remains a vital deciding element in its assembly rate. Our study provides unexpected insights on OMP assembly and the functional relevance of BamA in vivo.
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Affiliation(s)
- Pankaj B Tiwari
- Molecular Biophysics Laboratory, Department of Biological Sciences, Indian Institute of Science Education and Research, Bhopal, India
| | - Radhakrishnan Mahalakshmi
- Molecular Biophysics Laboratory, Department of Biological Sciences, Indian Institute of Science Education and Research, Bhopal, India
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35
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Lundquist K, Billings E, Bi M, Wellnitz J, Noinaj N. The assembly of β-barrel membrane proteins by BAM and SAM. Mol Microbiol 2020; 115:425-435. [PMID: 33314350 DOI: 10.1111/mmi.14666] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2020] [Revised: 12/11/2020] [Indexed: 12/31/2022]
Abstract
Gram-negative bacteria, mitochondria, and chloroplasts all possess an outer membrane populated with a host of β-barrel outer-membrane proteins (βOMPs). These βOMPs play crucial roles in maintaining viability of their hosts, and therefore, it is essential to understand the biogenesis of this class of membrane proteins. In recent years, significant structural and functional advancements have been made toward elucidating this process, which is mediated by the β-barrel assembly machinery (BAM) in Gram-negative bacteria, and by the sorting and assembly machinery (SAM) in mitochondria. Structures of both BAM and SAM have now been reported, allowing a comparison and dissection of the two machineries, with other studies reporting on functional aspects of each. Together, these new insights provide compelling support for the proposed budding mechanism, where each nascent βOMP forms a hybrid-barrel intermediate with BAM/SAM in route to its biogenesis into the membrane. Here, we will review these recent studies and highlight their contributions toward understanding βOMP biogenesis in Gram-negative bacteria and in mitochondria. We will also weigh the evidence supporting each of the two leading mechanistic models for how BAM/SAM function, and offer an outlook on future studies within the field.
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Affiliation(s)
- Karl Lundquist
- Department of Biological Sciences, Markey Center for Structural Biology, Purdue University, West Lafayette, IN, USA
| | - Evan Billings
- Department of Biological Sciences, Markey Center for Structural Biology, Purdue University, West Lafayette, IN, USA
| | - Maxine Bi
- Department of Biological Sciences, Markey Center for Structural Biology, Purdue University, West Lafayette, IN, USA
| | - James Wellnitz
- Department of Biological Sciences, Markey Center for Structural Biology, Purdue University, West Lafayette, IN, USA
| | - Nicholas Noinaj
- Department of Biological Sciences, Markey Center for Structural Biology, Purdue University, West Lafayette, IN, USA.,Purdue Institute of Inflammation, Immunology and Infectious Disease, Purdue University, West Lafayette, IN, USA
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36
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Iadanza MG, Schiffrin B, White P, Watson MA, Horne JE, Higgins AJ, Calabrese AN, Brockwell DJ, Tuma R, Kalli AC, Radford SE, Ranson NA. Distortion of the bilayer and dynamics of the BAM complex in lipid nanodiscs. Commun Biol 2020; 3:766. [PMID: 33318620 PMCID: PMC7736308 DOI: 10.1038/s42003-020-01419-w] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Accepted: 10/12/2020] [Indexed: 11/28/2022] Open
Abstract
The β-barrel assembly machinery (BAM) catalyses the folding and insertion of β-barrel outer membrane proteins (OMPs) into the outer membranes of Gram-negative bacteria by mechanisms that remain unclear. Here, we present an ensemble of cryoEM structures of the E. coli BamABCDE (BAM) complex in lipid nanodiscs, determined using multi-body refinement techniques. These structures, supported by single-molecule FRET measurements, describe a range of motions in the BAM complex, mostly localised within the periplasmic region of the major subunit BamA. The β-barrel domain of BamA is in a 'lateral open' conformation in all of the determined structures, suggesting that this is the most energetically favourable species in this bilayer. Strikingly, the BAM-containing lipid nanodisc is deformed, especially around BAM's lateral gate. This distortion is also captured in molecular dynamics simulations, and provides direct structural evidence for the lipid 'disruptase' activity of BAM, suggested to be an important part of its functional mechanism.
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Affiliation(s)
- Matthew G Iadanza
- Astbury Centre for Structural Molecular Biology, School of Molecular & Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Bob Schiffrin
- Astbury Centre for Structural Molecular Biology, School of Molecular & Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Paul White
- Astbury Centre for Structural Molecular Biology, School of Molecular & Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Matthew A Watson
- Astbury Centre for Structural Molecular Biology, School of Molecular & Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Jim E Horne
- Astbury Centre for Structural Molecular Biology, School of Molecular & Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Anna J Higgins
- Astbury Centre for Structural Molecular Biology, School of Molecular & Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Antonio N Calabrese
- Astbury Centre for Structural Molecular Biology, School of Molecular & Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - David J Brockwell
- Astbury Centre for Structural Molecular Biology, School of Molecular & Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Roman Tuma
- Astbury Centre for Structural Molecular Biology, School of Molecular & Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
- Faculty of Science, University of South Bohemia, Ceske Budejovice, Czech Republic
| | - Antreas C Kalli
- Astbury Centre for Structural Molecular Biology, School of Molecular & Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Sheena E Radford
- Astbury Centre for Structural Molecular Biology, School of Molecular & Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK.
| | - Neil A Ranson
- Astbury Centre for Structural Molecular Biology, School of Molecular & Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK.
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Liu J, Gumbart JC. Membrane thinning and lateral gating are consistent features of BamA across multiple species. PLoS Comput Biol 2020; 16:e1008355. [PMID: 33112853 PMCID: PMC7652284 DOI: 10.1371/journal.pcbi.1008355] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Revised: 11/09/2020] [Accepted: 09/21/2020] [Indexed: 01/09/2023] Open
Abstract
In Gram-negative bacteria, the folding and insertion of β-barrel outer membrane proteins (OMPs) to the outer membrane are mediated by the β-barrel assembly machinery (BAM) complex. Two leading models of this process have been put forth: the hybrid barrel model, which claims that a lateral gate in BamA’s β-barrel can serve as a template for incoming OMPs, and the passive model, which claims that a thinned membrane near the lateral gate of BamA accelerates spontaneous OMP insertion. To examine the key elements of these two models, we have carried out 45.5 μs of equilibrium molecular dynamics simulations of BamA with and without POTRA domains from Escherichia coli, Salmonella enterica, Haemophilus ducreyi and Neisseria gonorrhoeae, together with BamA’s homolog, TamA from E. coli, in their native, species-specific outer membranes. In these equilibrium simulations, we consistently observe membrane thinning near the lateral gate for all proteins. We also see occasional spontaneous lateral gate opening and sliding of the β-strands at the gate interface for N. gonorrhoeae, indicating that the gate is dynamic. An additional 14 μs of free-energy calculations shows that the energy necessary to open the lateral gate in BamA/TamA varies by species, but is always lower than the Omp85 homolog, FhaC. Our combined results suggest OMP insertion utilizes aspects of both the hybrid barrel and passive models. Gram-negative bacteria such as Escherichia coli have a second, outer membrane surrounding them. This outer membrane provides an additional layer of protection, but also presents an additional challenge in its construction, exacerbated by the lack of chemical energy in this region of the bacterial cell. For example, proteins in the outer membrane are inserted via BamA, itself an integral membrane protein. The precise mechanisms by which BamA assists in the insertion process are still unclear. Here, we use extensive simulations in atomistic detail of BamA from multiple species in its native outer membrane environment to shed light on this process. We find that the lateral gate of BamA, a proposed pathway into the membrane, is dynamic, although to a degree varying by species. On the other hand, thinning of the outer membrane near BamA’s lateral gate is observed consistently across all simulations. We conclude that multiple features of BamA contribute to protein insertion into the outer membrane.
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Affiliation(s)
- Jinchan Liu
- School of Physics, Georgia Institute of Technology, Atlanta, Georgia, United States of America
- Tang Aoqing Honors Program in Science, College of Chemistry, Jilin University, Changchun, Jilin Province, China
| | - James C. Gumbart
- School of Physics, Georgia Institute of Technology, Atlanta, Georgia, United States of America
- * E-mail:
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38
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Functions of the BamBCDE Lipoproteins Revealed by Bypass Mutations in BamA. J Bacteriol 2020; 202:JB.00401-20. [PMID: 32817097 DOI: 10.1128/jb.00401-20] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Accepted: 08/13/2020] [Indexed: 12/27/2022] Open
Abstract
The heteropentomeric β-barrel assembly machine (BAM complex) is responsible for folding and inserting a diverse array of β-barrel outer membrane proteins (OMPs) into the outer membrane (OM) of Gram-negative bacteria. The BAM complex contains two essential proteins, the β-barrel OMP BamA and a lipoprotein BamD, whereas the auxiliary lipoproteins BamBCE are individually nonessential. Here, we identify and characterize three bamA mutations, the E-to-K change at position 470 (bamAE470K ), the A-to-P change at position 496 (bamAA496P ), and the A-to-S change at position 499 (bamAA499S ), that suppress the otherwise lethal ΔbamD, ΔbamB ΔbamC ΔbamE, and ΔbamC ΔbamD ΔbamE mutations. The viability of cells lacking different combinations of BAM complex lipoproteins provides the opportunity to examine the role of the individual proteins in OMP assembly. Results show that, in wild-type cells, BamBCE share a redundant function; at least one of these lipoproteins must be present to allow BamD to coordinate productively with BamA. Besides BamA regulation, BamD shares an additional essential function that is redundant with a second function of BamB. Remarkably, bamAE470K suppresses both, allowing the construction of a BAM complex composed solely of BamAE470K that is able to assemble OMPs in the absence of BamBCDE. This work demonstrates that the BAM complex lipoproteins do not participate in the catalytic folding of OMP substrates but rather function to increase the efficiency of the assembly process by coordinating and regulating the assembly of diverse OMP substrates.IMPORTANCE The folding and insertion of β-barrel outer membrane proteins (OMPs) are conserved processes in mitochondria, chloroplasts, and Gram-negative bacteria. In Gram-negative bacteria, OMPs are assembled into the outer membrane (OM) by the heteropentomeric β-barrel assembly machine (BAM complex). In this study, we probe the function of the individual BAM proteins and how they coordinate assembly of a diverse family of OMPs. Furthermore, we identify a gain-of-function bamA mutant capable of assembling OMPs independently of all four other BAM proteins. This work advances our understanding of OMP assembly and sheds light on how this process is distinct in Gram-negative bacteria.
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39
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Collet JF, Cho SH, Iorga BI, Goemans CV. How the assembly and protection of the bacterial cell envelope depend on cysteine residues. J Biol Chem 2020; 295:11984-11994. [PMID: 32487747 PMCID: PMC7443483 DOI: 10.1074/jbc.rev120.011201] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Revised: 06/02/2020] [Indexed: 12/15/2022] Open
Abstract
The cell envelope of Gram-negative bacteria is a multilayered structure essential for bacterial viability; the peptidoglycan cell wall provides shape and osmotic protection to the cell, and the outer membrane serves as a permeability barrier against noxious compounds in the external environment. Assembling the envelope properly and maintaining its integrity are matters of life and death for bacteria. Our understanding of the mechanisms of envelope assembly and maintenance has increased tremendously over the past two decades. Here, we review the major achievements made during this time, giving central stage to the amino acid cysteine, one of the least abundant amino acid residues in proteins, whose unique chemical and physical properties often critically support biological processes. First, we review how cysteines contribute to envelope homeostasis by forming stabilizing disulfides in crucial bacterial assembly factors (LptD, BamA, and FtsN) and stress sensors (RcsF and NlpE). Second, we highlight the emerging role of enzymes that use cysteine residues to catalyze reactions that are necessary for proper envelope assembly, and we also explain how these enzymes are protected from oxidative inactivation. Finally, we suggest future areas of investigation, including a discussion of how cysteine residues could contribute to envelope homeostasis by functioning as redox switches. By highlighting the redox pathways that are active in the envelope of Escherichia coli, we provide a timely overview of the assembly of a cellular compartment that is the hallmark of Gram-negative bacteria.
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Affiliation(s)
| | - Seung-Hyun Cho
- de Duve Institute, UCLouvain, Brussels, Belgium; WELBIO, Brussels, Belgium
| | - Bogdan I Iorga
- de Duve Institute, UCLouvain, Brussels, Belgium; Université Paris-Saclay, CNRS UPR 2301, Institut de Chimie des Substances Naturelles, Gif-sur-Yvette, France
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40
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Horne JE, Brockwell DJ, Radford SE. Role of the lipid bilayer in outer membrane protein folding in Gram-negative bacteria. J Biol Chem 2020; 295:10340-10367. [PMID: 32499369 PMCID: PMC7383365 DOI: 10.1074/jbc.rev120.011473] [Citation(s) in RCA: 75] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Revised: 06/03/2020] [Indexed: 01/09/2023] Open
Abstract
β-Barrel outer membrane proteins (OMPs) represent the major proteinaceous component of the outer membrane (OM) of Gram-negative bacteria. These proteins perform key roles in cell structure and morphology, nutrient acquisition, colonization and invasion, and protection against external toxic threats such as antibiotics. To become functional, OMPs must fold and insert into a crowded and asymmetric OM that lacks much freely accessible lipid. This feat is accomplished in the absence of an external energy source and is thought to be driven by the high thermodynamic stability of folded OMPs in the OM. With such a stable fold, the challenge that bacteria face in assembling OMPs into the OM is how to overcome the initial energy barrier of membrane insertion. In this review, we highlight the roles of the lipid environment and the OM in modulating the OMP-folding landscape and discuss the factors that guide folding in vitro and in vivo We particularly focus on the composition, architecture, and physical properties of the OM and how an understanding of the folding properties of OMPs in vitro can help explain the challenges they encounter during folding in vivo Current models of OMP biogenesis in the cellular environment are still in flux, but the stakes for improving the accuracy of these models are high. OMP folding is an essential process in all Gram-negative bacteria, and considering the looming crisis of widespread microbial drug resistance it is an attractive target. To bring down this vital OMP-supported barrier to antibiotics, we must first understand how bacterial cells build it.
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Affiliation(s)
- Jim E Horne
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - David J Brockwell
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
| | - Sheena E Radford
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
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41
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The gain-of-function allele bamA E470K bypasses the essential requirement for BamD in β-barrel outer membrane protein assembly. Proc Natl Acad Sci U S A 2020; 117:18737-18743. [PMID: 32675245 DOI: 10.1073/pnas.2007696117] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The outer membrane (OM) of gram-negative bacteria confers innate resistance to toxins and antibiotics. Integral β-barrel outer membrane proteins (OMPs) function to establish and maintain the selective permeability of the OM. OMPs are assembled into the OM by the β-barrel assembly machine (BAM), which is composed of one OMP-BamA-and four lipoproteins-BamB, C, D, and E. BamB, C, and E can be removed individually with only minor effects on barrier function; however, depletion of either BamA or BamD causes a global defect in OMP assembly and results in cell death. We have identified a gain-of-function mutation, bamA E470K , that bypasses the requirement for BamD. Although bamD::kan bamA E470K cells exhibit growth and OM barrier defects, they assemble OMPs with surprising robustness. Our results demonstrate that BamD does not play a catalytic role in OMP assembly, but rather functions to regulate the activity of BamA.
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42
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Diederichs KA, Ni X, Rollauer SE, Botos I, Tan X, King MS, Kunji ERS, Jiang J, Buchanan SK. Structural insight into mitochondrial β-barrel outer membrane protein biogenesis. Nat Commun 2020; 11:3290. [PMID: 32620929 PMCID: PMC7335169 DOI: 10.1038/s41467-020-17144-1] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Accepted: 06/13/2020] [Indexed: 11/09/2022] Open
Abstract
In mitochondria, β-barrel outer membrane proteins mediate protein import, metabolite transport, lipid transport, and biogenesis. The Sorting and Assembly Machinery (SAM) complex consists of three proteins that assemble as a 1:1:1 complex to fold β-barrel proteins and insert them into the mitochondrial outer membrane. We report cryoEM structures of the SAM complex from Myceliophthora thermophila, which show that Sam50 forms a 16-stranded transmembrane β-barrel with a single polypeptide-transport-associated (POTRA) domain extending into the intermembrane space. Sam35 and Sam37 are located on the cytosolic side of the outer membrane, with Sam35 capping Sam50, and Sam37 interacting extensively with Sam35. Sam35 and Sam37 each adopt a GST-like fold, with no functional, structural, or sequence similarity to their bacterial counterparts. Structural analysis shows how the Sam50 β-barrel opens a lateral gate to accommodate its substrates.
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Affiliation(s)
- Kathryn A Diederichs
- Laboratory of Molecular Biology, National Institute of Diabetes & Digestive & Kidney Diseases, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD, 20892, USA
| | - Xiaodan Ni
- Laboratory of Membrane Proteins and Structural Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Sarah E Rollauer
- Laboratory of Molecular Biology, National Institute of Diabetes & Digestive & Kidney Diseases, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD, 20892, USA
- MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge Biomedical Campus, Cambridge, CB2 0XY, UK
- Vertex Pharmaceuticals, 50 Northern Avenue, Boston, MA, 02210, USA
| | - Istvan Botos
- Laboratory of Molecular Biology, National Institute of Diabetes & Digestive & Kidney Diseases, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD, 20892, USA
| | - Xiaofeng Tan
- Laboratory of Membrane Proteins and Structural Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Martin S King
- MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge Biomedical Campus, Cambridge, CB2 0XY, UK
| | - Edmund R S Kunji
- MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge Biomedical Campus, Cambridge, CB2 0XY, UK
| | - Jiansen Jiang
- Laboratory of Membrane Proteins and Structural Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA.
| | - Susan K Buchanan
- Laboratory of Molecular Biology, National Institute of Diabetes & Digestive & Kidney Diseases, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD, 20892, USA.
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43
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Jin F. The transmembrane supercomplex mediating the biogenesis of OMPs in Gram-negative bacteria assumes a circular conformational change upon activation. FEBS Open Bio 2020; 10:1698-1715. [PMID: 32602996 PMCID: PMC7396438 DOI: 10.1002/2211-5463.12922] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Revised: 06/15/2020] [Accepted: 06/15/2020] [Indexed: 11/06/2022] Open
Abstract
The cell envelope of Gram-negative bacteria is composed of the inner (plasma) and the outer membrane. In the outer membrane, the outer membrane β-barrel proteins (OMPs) serve multiple functions. They are synthesized in the cytoplasm and finally inserted into the outer membrane through a critical and complex pathway facilitated by many protein factors. Recently, a new model for the biogenesis of OMPs in Gram-negative bacteria was proposed, in which a supercomplex containing multiple proteins spans the inner and outer membrane, to mediate the biogenesis of OMPs. The core part of the transmembrane supercomplex is the inner membrane protein translocon and the outer membrane β-barrel assembly machinery (BAM) complex. Some components of the supercomplex, such as the BamA subunit of the BAM complex, are essential and conserved across species. The other components, for example, the BamB subunit and the primary periplasmic chaperone SurA, are also required for the supercomplex to gain complete function and full efficiency. How BamB and SurA behave in the supercomplex, however, is less well understood. Therefore, the crosstalk between BamA, BamB and SurA was investigated mainly through in vivo protein photo-cross-linking experiments and protein modeling. Moreover, theoretical structures for part of the supercomplex consisting of SurA and the BAM complex were constructed. The modeling data are consistent with the experimental results. The theoretical structures computed in this work provide a more comprehensive view of the mechanism of the supercomplex, demonstrating a circular conformational change of the supercomplex when it is active.
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Affiliation(s)
- Feng Jin
- School of Life Sciences, Peking University, Beijing, China.,Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, China
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44
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Rodríguez-Alonso R, Létoquart J, Nguyen VS, Louis G, Calabrese AN, Iorga BI, Radford SE, Cho SH, Remaut H, Collet JF. Structural insight into the formation of lipoprotein-β-barrel complexes. Nat Chem Biol 2020; 16:1019-1025. [PMID: 32572278 PMCID: PMC7610366 DOI: 10.1038/s41589-020-0575-0] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Accepted: 05/15/2020] [Indexed: 12/14/2022]
Abstract
The β-barrel assembly machinery (BAM) inserts outer membrane β-barrel proteins (OMPs) in the outer membrane of Gram-negative bacteria. In Enterobacteriacea, BAM also mediates export of the stress sensor lipoprotein RcsF to the cell surface by assembling RcsF-OMP complexes. Here, we report the crystal structure of the key BAM component BamA in complex with RcsF. BamA adopts an inward-open conformation, with the lateral gate to the membrane closed. RcsF is lodged deep inside the lumen of the BamA barrel, binding regions proposed to undergo an outward and lateral opening during OMP insertion. On the basis of our structural and biochemical data, we propose a push-and-pull model for RcsF export upon conformational cycling of BamA and provide a mechanistic explanation for how RcsF uses its interaction with BamA to detect envelope stress. Our data also suggest that the flux of incoming OMP substrates is involved in the control of BAM activity.
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Affiliation(s)
- Raquel Rodríguez-Alonso
- Walloon Excellence in Life Sciences and Biotechnology, Brussels, Belgium.,de Duve Institute, Université catholique de Louvain, Brussels, Belgium
| | - Juliette Létoquart
- Walloon Excellence in Life Sciences and Biotechnology, Brussels, Belgium.,de Duve Institute, Université catholique de Louvain, Brussels, Belgium
| | - Van Son Nguyen
- Structural Biology Brussels, Vrije Universiteit Brussel, Brussels, Belgium.,Structural and Molecular Microbiology, Structural Biology Research Center, VIB, Brussels, Belgium
| | - Gwennaelle Louis
- Walloon Excellence in Life Sciences and Biotechnology, Brussels, Belgium.,de Duve Institute, Université catholique de Louvain, Brussels, Belgium
| | - Antonio N Calabrese
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, UK
| | - Bogdan I Iorga
- de Duve Institute, Université catholique de Louvain, Brussels, Belgium.,Université Paris-Saclay, Institut de Chimie des Substances Naturelles, Gif-sur-Yvette, France
| | - Sheena E Radford
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, UK
| | - Seung-Hyun Cho
- Walloon Excellence in Life Sciences and Biotechnology, Brussels, Belgium. .,de Duve Institute, Université catholique de Louvain, Brussels, Belgium.
| | - Han Remaut
- Structural Biology Brussels, Vrije Universiteit Brussel, Brussels, Belgium. .,Structural and Molecular Microbiology, Structural Biology Research Center, VIB, Brussels, Belgium.
| | - Jean-François Collet
- Walloon Excellence in Life Sciences and Biotechnology, Brussels, Belgium. .,de Duve Institute, Université catholique de Louvain, Brussels, Belgium.
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45
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Tomasek D, Rawson S, Lee J, Wzorek JS, Harrison SC, Li Z, Kahne D. Structure of a nascent membrane protein as it folds on the BAM complex. Nature 2020; 583:473-478. [PMID: 32528179 PMCID: PMC7367713 DOI: 10.1038/s41586-020-2370-1] [Citation(s) in RCA: 83] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Accepted: 03/25/2020] [Indexed: 11/09/2022]
Abstract
Mitochondria, chloroplasts, and Gram-negative bacteria are encased in a double layer of membranes. The outer membrane contains proteins with a β-barrel structure1,2. β-barrels are sheets of β-strands wrapped into a cylinder with the first strand hydrogen-bonded to the last strand. Conserved multi-subunit molecular machines fold and insert these proteins into the outer membrane3–5. One subunit of the machines is itself a β-barrel protein that plays a central role in folding other β-barrels. In Gram-negative bacteria, the β-barrel assembly machine (Bam) consists of the β-barrel protein BamA and four lipoproteins5–8. To understand how the Bam complex accelerates folding without using exogenous energy (e.g., ATP)9, we trapped folding intermediates on the machine. We report here the structure of the Bam complex folding BamA itself. The BamA catalyst (BamAM, for BamAmachine) forms an asymmetric hybrid β-barrel with the BamA substrate (BamAS). The N-terminal edge of BamAM has an antiparallel hydrogen-bonded interface with the C-terminal edge of BamAS, consistent with previous crosslinking studies10–12; the other edges of BamAM and BamAS are close to each other but curl inward and do not pair. Six hydrogen bonds in a membrane environment make the interface between the two proteins very stable. This stability allows folding but creates a high kinetic barrier to substrate release once folding has finished. Features at each end of the substrate overcome the barrier and promote release by stepwise exchange of hydrogen bonds. This mechanism of substrate-assisted product release explains how the Bam complex can stably associate with the substrate during folding and then turn over rapidly when folding is complete.
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Affiliation(s)
- David Tomasek
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA, USA.,Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA
| | - Shaun Rawson
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA
| | - James Lee
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA, USA.,Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA.,Laboratory of Membrane Biophysics and Biology, The Rockefeller University, New York, NY, USA
| | - Joseph S Wzorek
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA.,Novartis Institutes for BioMedical Research, Cambridge, MA, USA
| | - Stephen C Harrison
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA. .,Howard Hughes Medical Institute, Boston, MA, USA.
| | - Zongli Li
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA. .,Howard Hughes Medical Institute, Boston, MA, USA.
| | - Daniel Kahne
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA, USA. .,Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA. .,Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA.
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46
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Dong S, Chu H, Wen K, Yu Q, Li H, Wang C, Qin X. Crystallization and X-ray analysis of Borrelia burgdorferi β-barrel assembly machinery A. Acta Crystallogr F Struct Biol Commun 2020; 76:235-240. [PMID: 32510463 PMCID: PMC7278503 DOI: 10.1107/s2053230x20006196] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Accepted: 05/06/2020] [Indexed: 11/10/2022] Open
Abstract
Mitochondria, chloroplasts and several species of bacteria have outer membrane proteins (OMPs) that perform many essential biological functions. The β-barrel assembly machinery (BAM) complex is one of the OMPs of Borrelia burgdorferi, the pathogenic spirochete that causes Lyme disease, and its BamA component (BbBamA) includes a C-terminal β-barrel domain and five N-terminal periplasmic polypeptide-transport-associated (POTRA) domains, which together perform a central transport function. In the current work, the production, crystallization and X-ray analysis of the three N-terminal POTRA domains of BbBamA (BbBamA-POTRA P1-P3; residues 30-273) were carried out. The crystals of BbBamA-POTRA P1-P3 belonged to space group P21, with unit-cell parameters a = 45.353, b = 111.538, c = 64.376 Å, β = 99.913°. The Matthews coefficient was calculated to be 2.92 Å3 Da-1, assuming the presence of two molecules per asymmetric unit, and the corresponding solvent content was 57.9%. Owing to the absence of an ideal homology model, numerous attempts to solve the BbBamA-POTRA P1-P3 structure using molecular replacement (MR) failed. In order to solve the structure, further trials using selenomethionine derivatization are currently being carried out.
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Affiliation(s)
- Shishang Dong
- School of Biological Science and Technology, University of Jinan, Jinan, People’s Republic of China
| | - Hongguan Chu
- School of Biological Science and Technology, University of Jinan, Jinan, People’s Republic of China
| | - Kangning Wen
- School of Biological Science and Technology, University of Jinan, Jinan, People’s Republic of China
| | - Qianqian Yu
- School of Biological Science and Technology, University of Jinan, Jinan, People’s Republic of China
| | - Hui Li
- School of Biological Science and Technology, University of Jinan, Jinan, People’s Republic of China
| | - Changhui Wang
- School of Biological Science and Technology, University of Jinan, Jinan, People’s Republic of China
| | - Xiaochun Qin
- School of Biological Science and Technology, University of Jinan, Jinan, People’s Republic of China
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Pokharel P, Habouria H, Bessaiah H, Dozois CM. Serine Protease Autotransporters of the Enterobacteriaceae (SPATEs): Out and About and Chopping It Up. Microorganisms 2019; 7:E594. [PMID: 31766493 PMCID: PMC6956023 DOI: 10.3390/microorganisms7120594] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Accepted: 11/13/2019] [Indexed: 02/06/2023] Open
Abstract
Autotransporters are secreted proteins with multiple functions produced by a variety of Gram-negative bacteria. In Enterobacteriaceae, a subgroup of these autotransporters are the SPATEs (serine protease autotransporters of Enterobacteriaceae). SPATEs play a crucial role in survival and virulence of pathogens such as Escherichia coli and Shigella spp. and contribute to intestinal and extra-intestinal infections. These high molecular weight proteases are transported to the external milieu by the type Va secretion system and function as proteases with diverse substrate specificities and biological functions including adherence and cytotoxicity. Herein, we provide an overview of SPATEs and discuss recent findings on the biological roles of these secreted proteins, including proteolysis of substrates, adherence to cells, modulation of the immune response, and virulence in host models. In closing, we highlight recent insights into the regulation of expression of SPATEs that could be exploited to understand fundamental SPATE biology.
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Affiliation(s)
- Pravil Pokharel
- Institut National de Recherche Scientifique (INRS)-Centre Armand-Frappier Santé Biotechnologie, Laval, QC H7V 1B7, Canada; (P.P.); (H.H.); (H.B.)
- Centre de Recherche en Infectiologie Porcine et Avicole (CRIPA), Saint-Hyacinthe, QC J2S 2M2, Canada
| | - Hajer Habouria
- Institut National de Recherche Scientifique (INRS)-Centre Armand-Frappier Santé Biotechnologie, Laval, QC H7V 1B7, Canada; (P.P.); (H.H.); (H.B.)
- Centre de Recherche en Infectiologie Porcine et Avicole (CRIPA), Saint-Hyacinthe, QC J2S 2M2, Canada
| | - Hicham Bessaiah
- Institut National de Recherche Scientifique (INRS)-Centre Armand-Frappier Santé Biotechnologie, Laval, QC H7V 1B7, Canada; (P.P.); (H.H.); (H.B.)
- Centre de Recherche en Infectiologie Porcine et Avicole (CRIPA), Saint-Hyacinthe, QC J2S 2M2, Canada
| | - Charles M. Dozois
- Institut National de Recherche Scientifique (INRS)-Centre Armand-Frappier Santé Biotechnologie, Laval, QC H7V 1B7, Canada; (P.P.); (H.H.); (H.B.)
- Centre de Recherche en Infectiologie Porcine et Avicole (CRIPA), Saint-Hyacinthe, QC J2S 2M2, Canada
- Institut Pasteur International Network, Laval, QC H7V 1B7, Canada
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48
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Lee J, Tomasek D, Santos TM, May MD, Meuskens I, Kahne D. Formation of a β-barrel membrane protein is catalyzed by the interior surface of the assembly machine protein BamA. eLife 2019; 8:49787. [PMID: 31724945 PMCID: PMC6887485 DOI: 10.7554/elife.49787] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2019] [Accepted: 11/13/2019] [Indexed: 01/02/2023] Open
Abstract
The β-barrel assembly machine (Bam) complex in Gram-negative bacteria and its counterparts in mitochondria and chloroplasts fold and insert outer membrane β-barrel proteins. BamA, an essential component of the complex, is itself a β-barrel and is proposed to play a central role in assembling other barrel substrates. Here, we map the path of substrate insertion by the Bam complex using site-specific crosslinking to understand the molecular mechanisms that control β-barrel folding and release. We find that the C-terminal strand of the substrate is stably held by BamA and that the N-terminal strands of the substrate are assembled inside the BamA β-barrel. Importantly, we identify contacts between the assembling β-sheet and the BamA interior surface that determine the rate of substrate folding. Our results support a model in which the interior wall of BamA acts as a chaperone to catalyze β-barrel assembly.
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Affiliation(s)
- James Lee
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, United States.,Department of Chemistry and Chemical Biology, Harvard University, Cambridge, United States
| | - David Tomasek
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, United States.,Department of Chemistry and Chemical Biology, Harvard University, Cambridge, United States
| | - Thiago Ma Santos
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, United States
| | - Mary D May
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, United States
| | - Ina Meuskens
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, United States
| | - Daniel Kahne
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, United States.,Department of Chemistry and Chemical Biology, Harvard University, Cambridge, United States
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49
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Ma X, Wang Q, Li Y, Tan P, Wu H, Wang P, Dong X, Hong L, Meng G. How BamA recruits OMP substrates via poly-POTRAs domain. FASEB J 2019; 33:14690-14702. [PMID: 31702961 DOI: 10.1096/fj.201900681rr] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Almost all the outer membrane proteins (OMPs) fold into an invariant β-barrel fold via the polypeptide-transport-associated (POTRA) motif and β-barrel assembly machinery (BAM). However, whether and how poly-POTRAs interact with OMPs remain largely unknown. Here, we have characterized the structures of Haemophilus influenzae poly-POTRAs via X-ray crystallography, small angle X-ray scattering, and molecular dynamics simulation. Unexpectedly, crystal packing reveals a putative OMP travel pathway spiraled by the conserved α2-β2 edges in poly-POTRAs. Supportively, the structure-based mutations targeting the OMP binding sites significantly disrupt OMP biogenesis, resulting in severe cell growth defects. Another notable feature in H. influenzae POTRA structures is flexibility. As characterized by ELISA assays, poly-POTRAs could recruit OMP substrates in a step-wise manner. More importantly, the restriction of POTRA-POTRA linkage and flexibility significantly impairs the BamA function and causes cell growth defect. Altogether, these results suggest that the β-strand augmentations and intrinsic flexibility are important factors for BamA-OMP recruitment.-Ma, X., Wang, Q., Li, Y., Tan, P., Wu, H., Wang, P., Dong, X., Hong, L., Meng, G. How BamA recruits OMP substrates via poly-POTRAs domain.
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Affiliation(s)
- Xiaodan Ma
- State Key Laboratory of Medical Genomics, Shanghai Institute of Hematology, Rui-Jin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Qianqian Wang
- State Key Laboratory of Medical Genomics, Shanghai Institute of Hematology, Rui-Jin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Yuwen Li
- State Key Laboratory of Medical Genomics, Shanghai Institute of Hematology, Rui-Jin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Pan Tan
- School of Physics and Astronomy, Institute of Natural Sciences, Shanghai Jiao Tong University, Shanghai, China
| | - Haiyan Wu
- State Key Laboratory of Medical Genomics, Shanghai Institute of Hematology, Rui-Jin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Pengran Wang
- State Key Laboratory of Medical Genomics, Shanghai Institute of Hematology, Rui-Jin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai Jiao Tong University, Shanghai, China.,Institute of Translational Medicine, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Xue Dong
- State Key Laboratory of Medical Genomics, Shanghai Institute of Hematology, Rui-Jin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Liang Hong
- School of Physics and Astronomy, Institute of Natural Sciences, Shanghai Jiao Tong University, Shanghai, China
| | - Guoyu Meng
- State Key Laboratory of Medical Genomics, Shanghai Institute of Hematology, Rui-Jin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai Jiao Tong University, Shanghai, China
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50
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Gunasinghe SD, Shiota T, Stubenrauch CJ, Schulze KE, Webb CT, Fulcher AJ, Dunstan RA, Hay ID, Naderer T, Whelan DR, Bell TDM, Elgass KD, Strugnell RA, Lithgow T. The WD40 Protein BamB Mediates Coupling of BAM Complexes into Assembly Precincts in the Bacterial Outer Membrane. Cell Rep 2019; 23:2782-2794. [PMID: 29847806 DOI: 10.1016/j.celrep.2018.04.093] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Revised: 03/05/2018] [Accepted: 04/23/2018] [Indexed: 01/28/2023] Open
Abstract
The β-barrel assembly machinery (BAM) complex is essential for localization of surface proteins on bacterial cells, but the mechanism by which it functions is unclear. We developed a direct stochastic optical reconstruction microscopy (dSTORM) methodology to view the BAM complex in situ. Single-cell analysis showed that discrete membrane precincts housing several BAM complexes are distributed across the E. coli surface, with a nearest neighbor distance of ∼200 nm. The auxiliary lipoprotein subunit BamB was crucial for this spatial distribution, and in situ crosslinking shows that BamB makes intimate contacts with BamA and BamB in neighboring BAM complexes within the precinct. The BAM complex precincts swell when outer membrane protein synthesis is maximal, visual proof that the precincts are active in protein assembly. This nanoscale interrogation of the BAM complex in situ suggests a model whereby bacterial outer membranes contain highly organized assembly precincts to drive integral protein assembly.
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Affiliation(s)
- Sachith D Gunasinghe
- Infection & Immunity Program, Biomedicine Discovery Institute, and Department of Microbiology, Monash University, Clayton, VIC 3800, Australia
| | - Takuya Shiota
- Infection & Immunity Program, Biomedicine Discovery Institute, and Department of Microbiology, Monash University, Clayton, VIC 3800, Australia; Organization for Promotion of Tenure Track, University of Miyazaki, Miyazaki 889-1692, Japan
| | - Christopher J Stubenrauch
- Infection & Immunity Program, Biomedicine Discovery Institute, and Department of Microbiology, Monash University, Clayton, VIC 3800, Australia
| | - Keith E Schulze
- Monash Micro Imaging, Monash University, Clayton, VIC 3800, Australia
| | - Chaille T Webb
- Infection & Immunity Program, Biomedicine Discovery Institute, and Department of Microbiology, Monash University, Clayton, VIC 3800, Australia
| | - Alex J Fulcher
- Infection & Immunity Program, Biomedicine Discovery Institute, and Department of Microbiology, Monash University, Clayton, VIC 3800, Australia; Monash Micro Imaging, Monash University, Clayton, VIC 3800, Australia; Infection & Immunity Program, Biomedicine Discovery Institute, and Department of Biochemistry & Molecular Biology, Monash University, Clayton, VIC 3800, Australia
| | - Rhys A Dunstan
- Infection & Immunity Program, Biomedicine Discovery Institute, and Department of Microbiology, Monash University, Clayton, VIC 3800, Australia
| | - Iain D Hay
- Infection & Immunity Program, Biomedicine Discovery Institute, and Department of Microbiology, Monash University, Clayton, VIC 3800, Australia
| | - Thomas Naderer
- Infection & Immunity Program, Biomedicine Discovery Institute, and Department of Biochemistry & Molecular Biology, Monash University, Clayton, VIC 3800, Australia
| | - Donna R Whelan
- School of Chemistry, Monash University, Clayton, VIC 3800, Australia; Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY, USA
| | - Toby D M Bell
- School of Chemistry, Monash University, Clayton, VIC 3800, Australia
| | - Kirstin D Elgass
- Monash Micro Imaging, Monash University, Clayton, VIC 3800, Australia; Hudson Institute of Medical Research, Clayton, VIC 3800, Australia
| | - Richard A Strugnell
- Department of Microbiology & Immunology, University of Melbourne, Parkville, VIC 3052, Australia
| | - Trevor Lithgow
- Infection & Immunity Program, Biomedicine Discovery Institute, and Department of Microbiology, Monash University, Clayton, VIC 3800, Australia.
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