1
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Elery ZK, Myers-Morales T, Phillips ED, Garcia EC. Relaxed specificity of BcpB transporters mediates interactions between Burkholderia cepacia complex contact-dependent growth inhibition systems. mSphere 2023; 8:e0030323. [PMID: 37498085 PMCID: PMC10449530 DOI: 10.1128/msphere.00303-23] [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: 06/07/2023] [Accepted: 06/11/2023] [Indexed: 07/28/2023] Open
Abstract
Belonging to the two-partner secretion family of proteins, contact-dependent growth inhibition (CDI) systems mediate interbacterial antagonism among closely related Gram-negative bacteria. The toxic portion of a large surface protein, BcpA/CdiA, is delivered to the cytoplasm of neighboring cells where it inhibits growth. Translocation of the antibacterial polypeptide out of the producing cell requires an associated outer membrane transporter, BcpB/CdiB. Some bacteria, including many Burkholderia species, encode multiple distinct CDI systems, but whether there is interaction between these systems is largely unknown. Using Burkholderia cepacia complex species as a model, here we show that related BcpB transporters exhibit considerable secretion flexibility and can secrete both cognate and non-cognate BcpA substrates. We also identified an additional unique Burkholderia dolosa CDI system capable of mediating interbacterial competition and demonstrated that its BcpB transporter has similar relaxed substrate specificity. Our results showed that two BcpB transporters (BcpB-2 and BcpB-3) were able to secrete all four of the B. dolosa BcpA toxins, while one transporter (BcpB-1) appeared unable to secrete even its cognate BcpA substrate under the tested conditions. This flexibility provided a competitive advantage, as strains lacking the full repertoire of BcpB proteins had decreased CDI activity. Similar results were obtained in Burkholderia multivorans, suggesting that secretion flexibility may be a conserved feature of Burkholderia CDI systems. Together these findings suggest that the interaction between distinct CDI systems enhances the efficiency of bacterial antagonism. IMPORTANCE The Burkholderia cepacia complex (Bcc) is a group of related opportunistic bacterial pathogens that occupy a diverse range of ecological niches and exacerbate disease in patients with underlying conditions. Contact-dependent growth inhibition (CDI) system proteins, produced by Gram-negative bacteria, contain antagonistic properties that allow for intoxication of closely related neighboring bacteria via a secreted protein, BcpA. Multiple unique CDI systems can be found in the same bacterial strain, and here we show that these distinct systems interact in several Bcc species. Our findings suggest that the interaction between CDI system proteins is important for interbacterial toxicity. Understanding the mechanism of interplay between CDI systems provides further insight into the complexity of bacterial antagonism. Moreover, since many bacterial species are predicted to encode multiple CDI systems, this study suggests that interactions between these distinct systems likely contribute to the overall competitive fitness of these species.
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Affiliation(s)
- Zaria K. Elery
- University of Kentucky College of Medicine, Lexington, Kentucky, USA
| | | | - Erica D. Phillips
- University of Kentucky College of Medicine, Lexington, Kentucky, USA
| | - Erin C. Garcia
- University of Kentucky College of Medicine, Lexington, Kentucky, USA
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2
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Mayse LA, Movileanu L. Gating of β-Barrel Protein Pores, Porins, and Channels: An Old Problem with New Facets. Int J Mol Sci 2023; 24:12095. [PMID: 37569469 PMCID: PMC10418385 DOI: 10.3390/ijms241512095] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Revised: 07/23/2023] [Accepted: 07/25/2023] [Indexed: 08/13/2023] Open
Abstract
β barrels are ubiquitous proteins in the outer membranes of mitochondria, chloroplasts, and Gram-negative bacteria. These transmembrane proteins (TMPs) execute a wide variety of tasks. For example, they can serve as transporters, receptors, membrane-bound enzymes, as well as adhesion, structural, and signaling elements. In addition, multimeric β barrels are common structural scaffolds among many pore-forming toxins. Significant progress has been made in understanding the functional, structural, biochemical, and biophysical features of these robust and versatile proteins. One frequently encountered fundamental trait of all β barrels is their voltage-dependent gating. This process consists of reversible or permanent conformational transitions between a large-conductance, highly permeable open state and a low-conductance, solute-restrictive closed state. Several intrinsic molecular mechanisms and environmental factors modulate this universal property of β barrels. This review article outlines the typical signatures of voltage-dependent gating. Moreover, we discuss recent developments leading to a better qualitative understanding of the closure dynamics of these TMPs.
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Affiliation(s)
- Lauren A. Mayse
- Department of Physics, Syracuse University, 201 Physics Building, Syracuse, NY 13244, USA;
- Department of Biomedical and Chemical Engineering, Syracuse University, 223 Link Hall, Syracuse, NY 13244, USA
| | - Liviu Movileanu
- Department of Physics, Syracuse University, 201 Physics Building, Syracuse, NY 13244, USA;
- Department of Biomedical and Chemical Engineering, Syracuse University, 223 Link Hall, Syracuse, NY 13244, USA
- The BioInspired Institute, Syracuse University, Syracuse, NY 13244, USA
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3
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Srinivasan K, Erramilli SK, Chakravarthy S, Gonzalez A, Kossiakoff A, Noinaj N. Characterization of synthetic antigen binding fragments targeting Toc75 for the isolation of TOC in A. thaliana and P. sativum. Structure 2023; 31:595-606.e5. [PMID: 36977410 PMCID: PMC10164082 DOI: 10.1016/j.str.2023.03.002] [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: 07/15/2022] [Revised: 12/21/2022] [Accepted: 03/02/2023] [Indexed: 03/29/2023]
Abstract
Roughly 95% of the proteins that make up the chloroplast must be imported from the cytoplasm. The machinery responsible for the translocation of these cargo proteins is called the translocon at the outer membrane of chloroplast (TOC). The TOC core consists of three proteins, Toc34, Toc75, and Toc159; no high-resolution structure has been solved of fully assembled TOC from plants. Efforts toward determining the structure of the TOC have been hindered almost entirely by difficulties in producing sufficient yields for structural studies. In this study, we introduce an innovative method that utilizes synthetic antigen binding fragments (sABs) to isolate TOC directly from wild-type plant biomass including A. thaliana and P. sativum. Binding between the sABs and the POTRA domains was characterized by size-exclusion chromatography coupled with small-angle X-ray scattering (SEC-SAXS), X-ray crystallography, and isothermal titration calorimetry. We also demonstrate the isolation of the TOC from P. sativum, laying the framework for large-scale isolation and purification of TOC for functional and structural studies.
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Affiliation(s)
- Karthik Srinivasan
- Department of Biological Sciences, Purdue University, West Lafayette, IN, USA
| | - Satchal K Erramilli
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA
| | - Srinivas Chakravarthy
- The Biophysics Collaborative Access Team (BioCAT), Department of Biological Sciences, Illinois Institute of Technology, Chicago, IL, USA
| | - Adrian Gonzalez
- Department of Biological Sciences, Purdue University, West Lafayette, IN, USA
| | - Anthony Kossiakoff
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA
| | - Nicholas Noinaj
- Department of Biological Sciences, Purdue University, West Lafayette, IN, USA.
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4
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Golshani M, Rahman WU, Osickova A, Holubova J, Lora J, Balashova N, Sebo P, Osicka R. Filamentous Hemagglutinin of Bordetella pertussis Does Not Interact with the β 2 Integrin CD11b/CD18. Int J Mol Sci 2022; 23:12598. [PMID: 36293453 PMCID: PMC9604300 DOI: 10.3390/ijms232012598] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Revised: 10/17/2022] [Accepted: 10/18/2022] [Indexed: 01/04/2024] Open
Abstract
The pertussis agent Bordetella pertussis produces a number of virulence factors, of which the filamentous hemagglutinin (FhaB) plays a role in B. pertussis adhesion to epithelial and phagocytic cells. Moreover, FhaB was recently found to play a crucial role in nasal cavity infection and B. pertussis transmission to new hosts. The 367 kDa FhaB protein translocates through an FhaC pore to the outer bacterial surface and is eventually processed to a ~220 kDa N-terminal FHA fragment by the SphB1 protease. A fraction of the mature FHA then remains associated with bacterial cell surface, while most of FHA is shed into the bacterial environment. Previously reported indirect evidence suggested that FHA, or its precursor FhaB, may bind the β2 integrin CD11b/CD18 of human macrophages. Therefore, we assessed FHA binding to various cells producing or lacking the integrin and show that purified mature FHA does not bind CD11b/CD18. Further results then revealed that the adhesion of B. pertussis to cells does not involve an interaction between the bacterial surface-associated FhaB and/or mature FHA and the β2 integrin CD11b/CD18. In contrast, FHA binding was strongly inhibited at micromolar concentrations of heparin, corroborating that the cell binding of FHA is ruled by the interaction of its heparin-binding domain with sulfated glycosaminoglycans on the cell surface.
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Affiliation(s)
- Maryam Golshani
- Institute of Microbiology of the Czech Academy of Sciences, Videnska 1083, 142 20 Prague, Czech Republic
| | - Waheed Ur Rahman
- Institute of Microbiology of the Czech Academy of Sciences, Videnska 1083, 142 20 Prague, Czech Republic
| | - Adriana Osickova
- Institute of Microbiology of the Czech Academy of Sciences, Videnska 1083, 142 20 Prague, Czech Republic
| | - Jana Holubova
- Institute of Microbiology of the Czech Academy of Sciences, Videnska 1083, 142 20 Prague, Czech Republic
| | - Jinery Lora
- Department of Basic and Translational Sciences, School of Dental Medicine, University of Pennsylvania, 240 S. 40th St., Philadelphia, PA 19104, USA
| | - Nataliya Balashova
- Department of Basic and Translational Sciences, School of Dental Medicine, University of Pennsylvania, 240 S. 40th St., Philadelphia, PA 19104, USA
| | - Peter Sebo
- Institute of Microbiology of the Czech Academy of Sciences, Videnska 1083, 142 20 Prague, Czech Republic
| | - Radim Osicka
- Institute of Microbiology of the Czech Academy of Sciences, Videnska 1083, 142 20 Prague, Czech Republic
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5
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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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6
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Job V, Gomez-Valero L, Renier A, Rusniok C, Bouillot S, Chenal-Francisque V, Gueguen E, Adrait A, Robert-Genthon M, Jeannot K, Panchev P, Elsen S, Fauvarque MO, Couté Y, Buchrieser C, Attrée I. Genomic erosion and horizontal gene transfer shape functional differences of the ExlA toxin in Pseudomonas spp. iScience 2022; 25:104596. [PMID: 35789842 PMCID: PMC9250014 DOI: 10.1016/j.isci.2022.104596] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Revised: 03/15/2022] [Accepted: 06/08/2022] [Indexed: 12/31/2022] Open
Abstract
Two-partner secretion (TPS) is widespread in the bacterial world. The pore-forming TPS toxin ExlA of Pseudomonas aeruginosa is conserved in pathogenic and environmental Pseudomonas. While P. chlororaphis and P. entomophila displayed ExlA-dependent killing, P. putida did not cause damage to eukaryotic cells. ExlA proteins interacted with epithelial cell membranes; however, only ExlAPch induced the cleavage of the adhesive molecule E-cadherin. ExlA proteins participated in insecticidal activity toward the larvae of Galleria mellonella and the fly Drosophila melanogaster. Evolutionary analyses demonstrated that the differences in the C-terminal domains are partly due to horizontal movements of the operon within the genus Pseudomonas. Reconstruction of the evolutionary history revealed the complex horizontal acquisitions. Together, our results provide evidence that conserved TPS toxins in environmental Pseudomonas play a role in bacteria-insect interactions and discrete differences in CTDs may determine their specificity and mode of action toward eukaryotic cells. ExlA is a two-partner secreted toxin conserved across Pseudomonas spp. Environmental Pseudomonas strains encode ExlA with different cytotoxic activities ExlA of environmental Pseudomonas strains play a role in bacteria-insect interactions ExlBA operon shows a complex evolutionary history of horizontal gene transfer
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Affiliation(s)
- Viviana Job
- Université Grenoble Alpes, Institute of Structural Biology, Bacterial Pathogenesis and Cellular Responses Team, UMR5075 CNRS, IRIG, CEA, Grenoble, France
| | - Laura Gomez-Valero
- Institut Pasteur, Université de Paris, CNRS UMR 6047, Unité Biologie des Bactéries Intracellulaires, 75015 Paris, France
| | - Adèle Renier
- Université Grenoble Alpes, Institute of Structural Biology, Bacterial Pathogenesis and Cellular Responses Team, UMR5075 CNRS, IRIG, CEA, Grenoble, France
| | - Christophe Rusniok
- Institut Pasteur, Université de Paris, CNRS UMR 6047, Unité Biologie des Bactéries Intracellulaires, 75015 Paris, France
| | - Stephanie Bouillot
- Université Grenoble Alpes, Institute of Structural Biology, Bacterial Pathogenesis and Cellular Responses Team, UMR5075 CNRS, IRIG, CEA, Grenoble, France
| | - Viviane Chenal-Francisque
- Institut Pasteur, Université de Paris, CNRS UMR 6047, Unité Biologie des Bactéries Intracellulaires, 75015 Paris, France
| | - Erwan Gueguen
- University of Lyon, Université Lyon 1, INSA de Lyon, CNRS UMR 5240 Microbiologie Adaptation et Pathogénie, Lyon, France
| | - Annie Adrait
- Université Grenoble Alpes, INSERM, CEA, UMR BioSanté U1292, Grenoble, France
| | - Mylène Robert-Genthon
- Université Grenoble Alpes, Institute of Structural Biology, Bacterial Pathogenesis and Cellular Responses Team, UMR5075 CNRS, IRIG, CEA, Grenoble, France
| | - Katy Jeannot
- Centre National de Référence de la Résistance aux Antibiotiques, Laboratoire de Bactériologie, Centre Hospitalier Universitaire Jean Minjoz, UMR6249 CNRS, Université de Bourgogne-Franche Comté, Besançon, France
| | - Peter Panchev
- Université Grenoble Alpes, Institute of Structural Biology, Bacterial Pathogenesis and Cellular Responses Team, UMR5075 CNRS, IRIG, CEA, Grenoble, France
| | - Sylvie Elsen
- Université Grenoble Alpes, Institute of Structural Biology, Bacterial Pathogenesis and Cellular Responses Team, UMR5075 CNRS, IRIG, CEA, Grenoble, France
| | | | - Yohann Couté
- Université Grenoble Alpes, INSERM, CEA, UMR BioSanté U1292, Grenoble, France
- CNRS, CEA, FR2048, Grenoble, France
| | - Carmen Buchrieser
- Institut Pasteur, Université de Paris, CNRS UMR 6047, Unité Biologie des Bactéries Intracellulaires, 75015 Paris, France
- Corresponding author
| | - Ina Attrée
- Université Grenoble Alpes, Institute of Structural Biology, Bacterial Pathogenesis and Cellular Responses Team, UMR5075 CNRS, IRIG, CEA, Grenoble, France
- Corresponding author
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7
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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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8
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Cuthbert BJ, Hayes CS, Goulding CW. Functional and Structural Diversity of Bacterial Contact-Dependent Growth Inhibition Effectors. Front Mol Biosci 2022; 9:866854. [PMID: 35558562 PMCID: PMC9086364 DOI: 10.3389/fmolb.2022.866854] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Accepted: 03/07/2022] [Indexed: 12/25/2022] Open
Abstract
Bacteria live in complex communities and environments, competing for space and nutrients. Within their niche habitats, bacteria have developed various inter-bacterial mechanisms to compete and communicate. One such mechanism is contact-dependent growth inhibition (CDI). CDI is found in many Gram-negative bacteria, including several pathogens. These CDI+ bacteria encode a CdiB/CdiA two-partner secretion system that delivers inhibitory toxins into neighboring cells upon contact. Toxin translocation results in the growth inhibition of closely related strains and provides a competitive advantage to the CDI+ bacteria. CdiB, an outer-membrane protein, secretes CdiA onto the surface of the CDI+ bacteria. When CdiA interacts with specific target-cell receptors, CdiA delivers its C-terminal toxin region (CdiA-CT) into the target-cell. CdiA-CT toxin proteins display a diverse range of toxic functions, such as DNase, RNase, or pore-forming toxin activity. CDI+ bacteria also encode an immunity protein, CdiI, that specifically binds and neutralizes its cognate CdiA-CT, protecting the CDI+ bacteria from auto-inhibition. In Gram-negative bacteria, toxin/immunity (CdiA-CT/CdiI) pairs have highly variable sequences and functions, with over 130 predicted divergent toxin/immunity complex families. In this review, we will discuss biochemical and structural advances made in the characterization of CDI. This review will focus on the diverse array of CDI toxin/immunity complex structures together with their distinct toxin functions. Additionally, we will discuss the most recent studies on target-cell recognition and toxin entry, along with the discovery of a new member of the CDI loci. Finally, we will offer insights into how these diverse toxin/immunity complexes could be harnessed to fight human diseases.
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Affiliation(s)
- Bonnie J. Cuthbert
- Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA, United States
| | - Christopher S. Hayes
- Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA, United States
- Biomolecular Science and Engineering Program, University of California, Santa Barbara, Santa Barbara, CA, United States
| | - Celia W. Goulding
- Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA, United States
- Pharmaceutical Sciences, University of California, Irvine, Irvine, CA, United States
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9
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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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10
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Ritzmann N, Manioglu S, Hiller S, Müller DJ. Monitoring the antibiotic darobactin modulating the β-barrel assembly factor BamA. Structure 2021; 30:350-359.e3. [PMID: 34875215 DOI: 10.1016/j.str.2021.11.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Revised: 10/30/2021] [Accepted: 11/11/2021] [Indexed: 12/15/2022]
Abstract
The β-barrel assembly machinery (BAM) complex is an essential component of Escherichia coli that inserts and folds outer membrane proteins (OMPs). The natural antibiotic compound darobactin inhibits BamA, the central unit of BAM. Here, we employ dynamic single-molecule force spectroscopy (SMFS) to better understand the structure-function relationship of BamA and its inhibition by darobactin. The five N-terminal polypeptide transport (POTRA) domains show low mechanical, kinetic, and energetic stabilities. In contrast, the structural region linking the POTRA domains to the transmembrane β-barrel exposes the highest mechanical stiffness and lowest kinetic stability within BamA, thus indicating a mechano-functional role. Within the β-barrel, the four N-terminal β-hairpins H1-H4 expose the highest mechanical stabilities and stiffnesses, while the four C-terminal β-hairpins H5-H6 show lower stabilities and higher flexibilities. This asymmetry within the β-barrel suggests that substrates funneling into the lateral gate formed by β-hairpins H1 and H8 can force the flexible C-terminal β-hairpins to change conformations.
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Affiliation(s)
- Noah Ritzmann
- Department of Biosystems Science and Engineering, Eidgenössische Technische Hochschule (ETH) Zürich, Mattenstrasse 26, 4058 Basel, Switzerland
| | - Selen Manioglu
- Department of Biosystems Science and Engineering, Eidgenössische Technische Hochschule (ETH) Zürich, Mattenstrasse 26, 4058 Basel, Switzerland
| | - Sebastian Hiller
- Biozentrum, University of Basel, Spitalstrasse 41, 4056 Basel, Switzerland
| | - Daniel J Müller
- Department of Biosystems Science and Engineering, Eidgenössische Technische Hochschule (ETH) Zürich, Mattenstrasse 26, 4058 Basel, Switzerland.
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11
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Guérin J, Buchanan SK. Protein import and export across the bacterial outer membrane. Curr Opin Struct Biol 2021; 69:55-62. [PMID: 33901701 DOI: 10.1016/j.sbi.2021.03.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2020] [Revised: 03/09/2021] [Accepted: 03/21/2021] [Indexed: 01/06/2023]
Abstract
The bacterial outer membrane forms an impermeable barrier to the environment, but a wide variety of substances must cross it without compromising the membrane. Perhaps, the most fascinating transport phenomenon is the import and export of very large protein toxins using relatively small β-barrel proteins residing in the outer membrane. Progress has been made on three systems in recent years that shed light on this process. In this review, we summarize bacteriocin (toxin) import using TonB-dependent transporters and protein secretion by autotransporters and two partner secretion systems.
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Affiliation(s)
- Jérémy Guérin
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Susan K Buchanan
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, 20892, USA.
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12
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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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13
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Guerin J, Botos I, Zhang Z, Lundquist K, Gumbart JC, Buchanan SK. Structural insight into toxin secretion by contact-dependent growth inhibition transporters. eLife 2020; 9:58100. [PMID: 33089781 PMCID: PMC7644211 DOI: 10.7554/elife.58100] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Accepted: 10/21/2020] [Indexed: 12/13/2022] Open
Abstract
Bacterial contact-dependent growth inhibition (CDI) systems use a type Vb secretion mechanism to export large CdiA toxins across the outer membrane by dedicated outer membrane transporters called CdiB. Here, we report the first crystal structures of two CdiB transporters from Acinetobacter baumannii and Escherichia coli. CdiB transporters adopt a TpsB fold, containing a 16-stranded transmembrane β-barrel connected to two periplasmic domains. The lumen of the CdiB pore is occluded by an N-terminal α-helix and the conserved extracellular loop 6; these two elements adopt different conformations in the structures. We identified a conserved DxxG motif located on strand β1 that connects loop 6 through different networks of interactions. Structural modifications of DxxG induce rearrangement of extracellular loops and alter interactions with the N-terminal α-helix, preparing the system for α-helix ejection. Using structural biology, functional assays, and molecular dynamics simulations, we show how the barrel pore is primed for CdiA toxin secretion.
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Affiliation(s)
- Jeremy Guerin
- Laboratory of Molecular Biology, NIDDK, NIH, Bethesda, United States
| | - Istvan Botos
- Laboratory of Molecular Biology, NIDDK, NIH, Bethesda, United States
| | - Zijian Zhang
- School of Physics, Georgia Institute of Technology, Atlanta, Georgia
| | - Karl Lundquist
- School of Physics, Georgia Institute of Technology, Atlanta, Georgia
| | - James C Gumbart
- School of Physics, Georgia Institute of Technology, Atlanta, Georgia
| | - Susan K Buchanan
- Laboratory of Molecular Biology, NIDDK, NIH, Bethesda, United States
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14
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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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15
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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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16
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Abstract
In Gram-negative bacteria, the outer membrane contains primarily β-barrel transmembrane proteins and lipoproteins. The insertion and assembly of β-barrel outer-membrane proteins (OMPs) is mediated by the β-barrel assembly machinery (BAM) complex, the core component of which is the 16-stranded transmembrane β-barrel BamA. Recent studies have indicated a possible role played by the seam between the first and last β-barrel strands of BamA in the OMP insertion process through lateral gating and a destabilized membrane region. In this study, we have determined the stability and dynamics of the lateral gate through over 12.5 μs of equilibrium simulations and 4 μs of free-energy calculations. From the equilibrium simulations, we have identified a persistent kink in the C-terminal strand and observed spontaneous lateral-gate separation in a mimic of the native bacterial outer membrane. Free-energy calculations of lateral gate opening revealed a significantly lower barrier to opening in the C-terminal kinked conformation; mutagenesis experiments confirm the relevance of C-terminal kinking to BamA structure and function.
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17
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POTRA Domains, Extracellular Lid, and Membrane Composition Modulate the Conformational Stability of the β Barrel Assembly Factor BamA. Structure 2018; 26:987-996.e3. [PMID: 29861346 DOI: 10.1016/j.str.2018.04.017] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2018] [Revised: 03/30/2018] [Accepted: 04/27/2018] [Indexed: 11/21/2022]
Abstract
The core component BamA of the β barrel assembly machinery (BAM) adopts several conformations, which are thought to facilitate the insertion and folding of β barrel proteins into the bacterial outer membrane. Which factors alter the stability of these conformations remains to be quantified. Here, we apply single-molecule force spectroscopy to characterize the mechanical properties of BamA from Escherichia coli. In contrast to the N-terminal periplasmic polypeptide-transport-associated (POTRA) domains, the C-terminal transmembrane β barrel domain of BamA is mechanically much more stable. Exposed to mechanical stress this β barrel stepwise unfolds β hairpins until unfolding has been completed. Thereby, the mechanical stabilities of β barrel and β hairpins are modulated by the POTRA domains, the membrane composition and the extracellular lid closing the β barrel. We anticipate that these differences in stability, which are caused by factors contributing to BAM function, promote conformations of the BamA β barrel required to insert and fold outer membrane proteins.
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18
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Höhr AIC, Lindau C, Wirth C, Qiu J, Stroud DA, Kutik S, Guiard B, Hunte C, Becker T, Pfanner N, Wiedemann N. Membrane protein insertion through a mitochondrial β-barrel gate. Science 2018; 359:359/6373/eaah6834. [PMID: 29348211 DOI: 10.1126/science.aah6834] [Citation(s) in RCA: 96] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2016] [Revised: 10/12/2017] [Accepted: 12/14/2017] [Indexed: 11/02/2022]
Abstract
The biogenesis of mitochondria, chloroplasts, and Gram-negative bacteria requires the insertion of β-barrel proteins into the outer membranes. Homologous Omp85 proteins are essential for membrane insertion of β-barrel precursors. It is unknown if precursors are threaded through the Omp85-channel interior and exit laterally or if they are translocated into the membrane at the Omp85-lipid interface. We have mapped the interaction of a precursor in transit with the mitochondrial Omp85-channel Sam50 in the native membrane environment. The precursor is translocated into the channel interior, interacts with an internal loop, and inserts into the lateral gate by β-signal exchange. Transport through the Omp85-channel interior followed by release through the lateral gate into the lipid phase may represent a basic mechanism for membrane insertion of β-barrel proteins.
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Affiliation(s)
- Alexandra I C Höhr
- Institute of Biochemistry and Molecular Biology, Centre for Biochemistry and Molecular Cell Research (ZBMZ), Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany.,Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Caroline Lindau
- Institute of Biochemistry and Molecular Biology, Centre for Biochemistry and Molecular Cell Research (ZBMZ), Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany.,Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Christophe Wirth
- Institute of Biochemistry and Molecular Biology, Centre for Biochemistry and Molecular Cell Research (ZBMZ), Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany
| | - Jian Qiu
- Institute of Biochemistry and Molecular Biology, Centre for Biochemistry and Molecular Cell Research (ZBMZ), Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany
| | - David A Stroud
- Institute of Biochemistry and Molecular Biology, Centre for Biochemistry and Molecular Cell Research (ZBMZ), Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany
| | - Stephan Kutik
- Institute of Biochemistry and Molecular Biology, Centre for Biochemistry and Molecular Cell Research (ZBMZ), Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany
| | - Bernard Guiard
- Centre de Génétique Moléculaire, CNRS, 91190 Gif-sur-Yvette, France
| | - Carola Hunte
- Institute of Biochemistry and Molecular Biology, Centre for Biochemistry and Molecular Cell Research (ZBMZ), Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany.,BIOSS Centre for Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany
| | - Thomas Becker
- Institute of Biochemistry and Molecular Biology, Centre for Biochemistry and Molecular Cell Research (ZBMZ), Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany.,BIOSS Centre for Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany
| | - Nikolaus Pfanner
- Institute of Biochemistry and Molecular Biology, Centre for Biochemistry and Molecular Cell Research (ZBMZ), Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany.,BIOSS Centre for Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany
| | - Nils Wiedemann
- Institute of Biochemistry and Molecular Biology, Centre for Biochemistry and Molecular Cell Research (ZBMZ), Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany.,BIOSS Centre for Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany
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19
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Nicoludis JM, Gaudet R. Applications of sequence coevolution in membrane protein biochemistry. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2018; 1860:895-908. [PMID: 28993150 PMCID: PMC5807202 DOI: 10.1016/j.bbamem.2017.10.004] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2017] [Revised: 09/28/2017] [Accepted: 10/02/2017] [Indexed: 12/22/2022]
Abstract
Recently, protein sequence coevolution analysis has matured into a predictive powerhouse for protein structure and function. Direct methods, which use global statistical models of sequence coevolution, have enabled the prediction of membrane and disordered protein structures, protein complex architectures, and the functional effects of mutations in proteins. The field of membrane protein biochemistry and structural biology has embraced these computational techniques, which provide functional and structural information in an otherwise experimentally-challenging field. Here we review recent applications of protein sequence coevolution analysis to membrane protein structure and function and highlight the promising directions and future obstacles in these fields. We provide insights and guidelines for membrane protein biochemists who wish to apply sequence coevolution analysis to a given experimental system.
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Affiliation(s)
- John M Nicoludis
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, United States
| | - Rachelle Gaudet
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA, 02138, United States.
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20
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Translocation of lipoproteins to the surface of gram negative bacteria. Curr Opin Struct Biol 2018; 51:73-79. [PMID: 29579694 DOI: 10.1016/j.sbi.2018.03.006] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2017] [Revised: 03/06/2018] [Accepted: 03/07/2018] [Indexed: 11/21/2022]
Abstract
The surface of many Gram-negative bacteria contains lipidated protein molecules referred to as surface lipoproteins or SLPs. SLPs play critical roles in host immune evasion, nutrient acquisition and regulation of bacterial stress response, and have been extensively studied as vaccine antigens. The aim of this review is to summarize the recent studies that have investigated the biosynthetic and translocation pathways used by different bacterial species to deliver SLPs to the surface. We will specifically focus on Slam, a novel outer membrane protein first discovered in pathogenic Neisseria sp., that is involved in translocation of SLPs across the outer membrane.
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21
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Tommassen J, Arenas J. Biological Functions of the Secretome of Neisseria meningitidis. Front Cell Infect Microbiol 2017; 7:256. [PMID: 28670572 PMCID: PMC5472700 DOI: 10.3389/fcimb.2017.00256] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2017] [Accepted: 05/29/2017] [Indexed: 11/13/2022] Open
Abstract
Neisseria meningitidis is a Gram-negative bacterial pathogen that normally resides as a commensal in the human nasopharynx but occasionally causes disease with high mortality and morbidity. To interact with its environment, it transports many proteins across the outer membrane to the bacterial cell surface and into the extracellular medium for which it deploys the common and well-characterized autotransporter, two-partner and type I secretion mechanisms, as well as a recently discovered pathway for the surface exposure of lipoproteins. The surface-exposed and secreted proteins serve roles in host-pathogen interactions, including adhesion to host cells and extracellular matrix proteins, evasion of nutritional immunity imposed by iron-binding proteins of the host, prevention of complement activation, neutralization of antimicrobial peptides, degradation of immunoglobulins, and permeabilization of epithelial layers. Furthermore, they have roles in interbacterial interactions, including the formation and dispersal of biofilms and the suppression of the growth of bacteria competing for the same niche. Here, we will review the protein secretion systems of N. meningitidis and focus on the functions of the secreted proteins.
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Affiliation(s)
- Jan Tommassen
- Department of Molecular Microbiology and Institute of Biomembranes, Utrecht UniversityUtrecht, Netherlands
| | - Jesús Arenas
- Department of Molecular Microbiology and Institute of Biomembranes, Utrecht UniversityUtrecht, Netherlands
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22
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The POTRA domains of Toc75 exhibit chaperone-like function to facilitate import into chloroplasts. Proc Natl Acad Sci U S A 2017; 114:E4868-E4876. [PMID: 28559331 DOI: 10.1073/pnas.1621179114] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Protein trafficking across membranes is an essential function in cells; however, the exact mechanism for how this occurs is not well understood. In the endosymbionts, mitochondria and chloroplasts, the vast majority of proteins are synthesized in the cytoplasm as preproteins and then imported into the organelles via specialized machineries. In chloroplasts, protein import is accomplished by the TOC (translocon on the outer chloroplast membrane) and TIC (translocon on the inner chloroplast membrane) machineries in the outer and inner envelope membranes, respectively. TOC mediates initial recognition of preproteins at the outer membrane and includes a core membrane channel, Toc75, and two receptor proteins, Toc33/34 and Toc159, each containing GTPase domains that control preprotein binding and translocation. Toc75 is predicted to have a β-barrel fold consisting of an N-terminal intermembrane space (IMS) domain and a C-terminal 16-stranded β-barrel domain. Here we report the crystal structure of the N-terminal IMS domain of Toc75 from Arabidopsis thaliana, revealing three tandem polypeptide transport-associated (POTRA) domains, with POTRA2 containing an additional elongated helix not observed previously in other POTRA domains. Functional studies show an interaction with the preprotein, preSSU, which is mediated through POTRA2-3. POTRA2-3 also was found to have chaperone-like activity in an insulin aggregation assay, which we propose facilitates preprotein import. Our data suggest a model in which the POTRA domains serve as a binding site for the preprotein as it emerges from the Toc75 channel and provide a chaperone-like activity to prevent misfolding or aggregation as the preprotein traverses the intermembrane space.
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23
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Guérin J, Bigot S, Schneider R, Buchanan SK, Jacob-Dubuisson F. Two-Partner Secretion: Combining Efficiency and Simplicity in the Secretion of Large Proteins for Bacteria-Host and Bacteria-Bacteria Interactions. Front Cell Infect Microbiol 2017; 7:148. [PMID: 28536673 PMCID: PMC5422565 DOI: 10.3389/fcimb.2017.00148] [Citation(s) in RCA: 66] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Accepted: 04/10/2017] [Indexed: 12/31/2022] Open
Abstract
Initially identified in pathogenic Gram-negative bacteria, the two-partner secretion (TPS) pathway, also known as Type Vb secretion, mediates the translocation across the outer membrane of large effector proteins involved in interactions between these pathogens and their hosts. More recently, distinct TPS systems have been shown to secrete toxic effector domains that participate in inter-bacterial competition or cooperation. The effects of these systems are based on kin vs. non-kin molecular recognition mediated by specific immunity proteins. With these new toxin-antitoxin systems, the range of TPS effector functions has thus been extended from cytolysis, adhesion, and iron acquisition, to genome maintenance, inter-bacterial killing and inter-bacterial signaling. Basically, a TPS system is made up of two proteins, the secreted TpsA effector protein and its TpsB partner transporter, with possible additional factors such as immunity proteins for protection against cognate toxic effectors. Structural studies have indicated that TpsA proteins mainly form elongated β helices that may be followed by specific functional domains. TpsB proteins belong to the Omp85 superfamily. Open questions remain on the mechanism of protein secretion in the absence of ATP or an electrochemical gradient across the outer membrane. The remarkable dynamics of the TpsB transporters and the progressive folding of their TpsA partners at the bacterial surface in the course of translocation are thought to be key elements driving the secretion process.
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Affiliation(s)
- Jeremy Guérin
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of HealthBethesda, MD, USA
| | - Sarah Bigot
- Molecular Microbiology and Structural Biochemistry, Centre National de La Recherche Scientifique UMR 5086-Université Lyon 1, Institute of Biology and Chemistry of ProteinsLyon, France
| | - Robert Schneider
- NMR and Molecular Interactions, Université de Lille, Centre National de La Recherche Scientifique, UMR 8576-Unité de Glycobiologie Structurale et FonctionnelleLille, France
| | - Susan K Buchanan
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of HealthBethesda, MD, USA
| | - Françoise Jacob-Dubuisson
- Université de Lille, Centre National de La Recherche Scientifique, Institut National de La Santé et de La Recherche Médicale, CHU Lille, Institut Pasteur de Lille, U1019-UMR 8204-Centre d'Infection et d'Immunité de LilleLille, France
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24
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Pseudomonas aeruginosa Pore-Forming Exolysin and Type IV Pili Cooperate To Induce Host Cell Lysis. mBio 2017; 8:mBio.02250-16. [PMID: 28119472 PMCID: PMC5263249 DOI: 10.1128/mbio.02250-16] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Clinical strains of Pseudomonas aeruginosa lacking the type III secretion system genes employ a toxin, exolysin (ExlA), for host cell membrane disruption. Here, we demonstrated that ExlA export requires a predicted outer membrane protein, ExlB, showing that ExlA and ExlB define a new active two-partner secretion (TPS) system of P. aeruginosa In addition to the TPS signals, ExlA harbors several distinct domains, which include one hemagglutinin domain, five arginine-glycine-aspartic acid (RGD) motifs, and a C-terminal region lacking any identifiable sequence motifs. However, this C-terminal region is important for the toxic activity, since its deletion abolishes host cell lysis. Using lipid vesicles and eukaryotic cells, including red blood cells, we demonstrated that ExlA has a pore-forming activity which precedes cell membrane disruption of nucleated cells. Finally, we developed a high-throughput cell-based live-dead assay and used it to screen a transposon mutant library of an ExlA-producing P. aeruginosa clinical strain for bacterial factors required for ExlA-mediated toxicity. The screen resulted in the identification of proteins involved in the formation of type IV pili as being required for ExlA to exert its cytotoxic activity by promoting close contact between bacteria and the host cell. These findings represent the first example of cooperation between a pore-forming toxin of the TPS family and surface appendages in host cell intoxication. IMPORTANCE The course and outcome of acute, toxigenic infections by Pseudomonas aeruginosa clinical isolates rely on the deployment of one of two virulence strategies: delivery of effectors by the well-known type III secretion system or the cytolytic activity of the recently identified two-partner secreted toxin, exolysin. Here, we characterize several features of the mammalian cell intoxication process mediated by exolysin. We found that exolysin requires the outer membrane protein ExlB for export into extracellular medium. Using in vitro recombinant protein and ex vivo assays, we demonstrated a pore-forming activity of exolysin. A cellular cytotoxicity screen of a transposon mutant library, made in an exolysin-producing clinical strain, identified type IV pili as bacterial appendages required for exolysin toxic function. This work deciphers molecular mechanisms underlying the activity of novel virulence factors used by P. aeruginosa clinical strains lacking the type III secretion system, including a requirement for the toxin-producing bacteria to be attached to the targeted cell to induce cytolysis, and defines new targets for developing antivirulence strategies.
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Bakelar J, Buchanan SK, Noinaj N. Structural snapshots of the β-barrel assembly machinery. FEBS J 2016; 284:1778-1786. [PMID: 27862971 DOI: 10.1111/febs.13960] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Revised: 11/01/2016] [Accepted: 11/10/2016] [Indexed: 11/29/2022]
Abstract
The β-barrel assembly machinery (BAM) is a multicomponent complex responsible for the biogenesis of β-barrel outer membrane proteins (OMPs) in Gram-negative bacteria, with conserved systems in both mitochondria and chloroplasts. Given its importance in the integrity of the outer membrane and in the assembly of surface exposed virulence factors, BAM is an attractive therapeutic target against pathogenic bacteria, particularly multidrug-resistant strains. While the mechanism for how BAM functions remains elusive, previous structural studies have described each of the individual components of BAM, offering only a few clues to how the complex functions. Recently, a number of structures have been reported of complexes, including that of fully assembled BAM in differing conformational states. These studies have provided the molecular blueprint detailing the atomic interactions between the components and have revealed new details about BAM, which suggest a dynamic mechanism that may use conformational changes to assist in the biogenesis of new OMPs.
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Affiliation(s)
- Jeremy Bakelar
- Department of Biological Sciences, Markey Center for Structural Biology, Purdue Institute for Inflammation, Immunology and Infectious Diseases, Purdue University, West Lafayette, IN, USA
| | - Susan K Buchanan
- National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Nicholas Noinaj
- Department of Biological Sciences, Markey Center for Structural Biology, Purdue Institute for Inflammation, Immunology and Infectious Diseases, Purdue University, West Lafayette, IN, USA
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26
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Henke K, Welte W, Hauser K. Direct Monitoring of β-Sheet Formation in the Outer Membrane Protein TtoA Assisted by TtOmp85. Biochemistry 2016; 55:4333-43. [PMID: 27400268 DOI: 10.1021/acs.biochem.6b00691] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy was applied to investigate the folding of an outer membrane protein, TtoA, assisted by TtOmp85, both from the thermophilic eubacterium Thermus thermophilus. To directly monitor the formation of β-sheet structure in TtoA and to analyze the function of TtOmp85, we immobilized unfolded TtoA on an ATR crystal. Interaction with TtOmp85 initiated TtoA folding as shown by time-dependent spectra recorded during the folding process. Our ATR-FTIR experiments prove that TtOmp85 possesses specific functionality to assist β-sheet formation of TtoA. We demonstrate the potential of this spectroscopic approach to study the interaction of outer membrane proteins in vitro and in a time-resolved manner.
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Affiliation(s)
- Katharina Henke
- Department of Chemistry, ‡Department of Biology, and §Konstanz Research School Chemical Biology, University of Konstanz , 78457 Konstanz, Germany
| | - Wolfram Welte
- Department of Chemistry, ‡Department of Biology, and §Konstanz Research School Chemical Biology, University of Konstanz , 78457 Konstanz, Germany
| | - Karin Hauser
- Department of Chemistry, ‡Department of Biology, and §Konstanz Research School Chemical Biology, University of Konstanz , 78457 Konstanz, Germany
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27
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Heinz E, Stubenrauch CJ, Grinter R, Croft NP, Purcell AW, Strugnell RA, Dougan G, Lithgow T. Conserved Features in the Structure, Mechanism, and Biogenesis of the Inverse Autotransporter Protein Family. Genome Biol Evol 2016; 8:1690-705. [PMID: 27190006 PMCID: PMC4943183 DOI: 10.1093/gbe/evw112] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The bacterial cell surface proteins intimin and invasin are virulence factors that share a common domain structure and bind selectively to host cell receptors in the course of bacterial pathogenesis. The β-barrel domains of intimin and invasin show significant sequence and structural similarities. Conversely, a variety of proteins with sometimes limited sequence similarity have also been annotated as “intimin-like” and “invasin” in genome datasets, while other recent work on apparently unrelated virulence-associated proteins ultimately revealed similarities to intimin and invasin. Here we characterize the sequence and structural relationships across this complex protein family. Surprisingly, intimins and invasins represent a very small minority of the sequence diversity in what has been previously the “intimin/invasin protein family”. Analysis of the assembly pathway for expression of the classic intimin, EaeA, and a characteristic example of the most prevalent members of the group, FdeC, revealed a dependence on the translocation and assembly module as a common feature for both these proteins. While the majority of the sequences in the grouping are most similar to FdeC, a further and widespread group is two-partner secretion systems that use the β-barrel domain as the delivery device for secretion of a variety of virulence factors. This comprehensive analysis supports the adoption of the “inverse autotransporter protein family” as the most accurate nomenclature for the family and, in turn, has important consequences for our overall understanding of the Type V secretion systems of bacterial pathogens.
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Affiliation(s)
- Eva Heinz
- Department of Microbiology, Infection & Immunity Program, Biomedicine Discovery Institute, Monash University, Clayton, Australia Wellcome Trust Sanger Institute, Hinxton, United Kingdom
| | - Christopher J Stubenrauch
- Department of Microbiology, Infection & Immunity Program, Biomedicine Discovery Institute, Monash University, Clayton, Australia
| | - Rhys Grinter
- Department of Microbiology, Infection & Immunity Program, Biomedicine Discovery Institute, Monash University, Clayton, Australia Institute of Microbiology and Infection, School of Immunity and Infection, University of Birmingham, Birmingham, United Kingdom
| | - Nathan P Croft
- Department of Biochemistry and Molecular Biology, Infection & Immunity Program, Biomedicine Discovery Institute, Monash University, Clayton, Australia
| | - Anthony W Purcell
- Department of Biochemistry and Molecular Biology, Infection & Immunity Program, Biomedicine Discovery Institute, Monash University, Clayton, Australia
| | - Richard A Strugnell
- Department of Microbiology & Immunology, University of Melbourne, Parkville, Australia
| | - Gordon Dougan
- Wellcome Trust Sanger Institute, Hinxton, United Kingdom
| | - Trevor Lithgow
- Department of Microbiology, Infection & Immunity Program, Biomedicine Discovery Institute, Monash University, Clayton, Australia
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28
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Plummer AM, Fleming KG. BamA Alone Accelerates Outer Membrane Protein Folding In Vitro through a Catalytic Mechanism. Biochemistry 2016; 54:6009-11. [PMID: 26394056 PMCID: PMC4613867 DOI: 10.1021/acs.biochem.5b00950] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
![]()
β-Barrel
assembly machinery protein A (BamA) plays a critical
role in the biogenesis of outer membrane proteins (OMPs); however,
a mechanistic understanding of its function is lacking. Here, we report
an in vitro assay that investigates whether the mechanism of BamA-catalyzed
OMP folding is stoichiometric or catalytic. We found that BamA accelerates
the folding of OMPs in vitro via a catalytic mechanism, similar to
the activity of the full multiprotein β-barrel assembly machinery
(BAM) complex in vivo. As BamA alone can repeatedly facilitate the
folding of OMPs, we suggest the additional BAM components accelerate
this basal activity to biologically relevant time scales.
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Affiliation(s)
- Ashlee M Plummer
- Thomas C. Jenkins Department of Biophysics, Johns Hopkins University , 3400 North Charles Street, Baltimore, Maryland 21218, United States
| | - Karen G Fleming
- Thomas C. Jenkins Department of Biophysics, Johns Hopkins University , 3400 North Charles Street, Baltimore, Maryland 21218, United States
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29
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Wimmer MR, Woods CN, Adamczak KJ, Glasgow EM, Novak WRP, Grilley DP, Weaver TM. Sequential unfolding of the hemolysin two-partner secretion domain from Proteus mirabilis. Protein Sci 2015; 24:1841-55. [PMID: 26350294 DOI: 10.1002/pro.2791] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2015] [Revised: 08/19/2015] [Accepted: 08/20/2015] [Indexed: 01/07/2023]
Abstract
Protein secretion is a major contributor to Gram-negative bacterial virulence. Type Vb or two-partner secretion (TPS) pathways utilize a membrane bound β-barrel B component (TpsB) to translocate large and predominantly virulent exoproteins (TpsA) through a nucleotide independent mechanism. We focused our studies on a truncated TpsA member termed hemolysin A (HpmA265), a structurally and functionally characterized TPS domain from Proteus mirabilis. Contrary to the expectation that the TPS domain of HpmA265 would denature in a single cooperative transition, we found that the unfolding follows a sequential model with three distinct transitions linking four states. The solvent inaccessible core of HpmA265 can be divided into two different regions. The C-proximal region contains nonpolar residues and forms a prototypical hydrophobic core as found in globular proteins. The N-proximal region of the solvent inaccessible core, however, contains polar residues. To understand the contributions of the hydrophobic and polar interiors to overall TPS domain stability, we conducted unfolding studies on HpmA265 and site-specific mutants of HpmA265. By correlating the effect of individual site-specific mutations with the sequential unfolding results we were able to divide the HpmA265 TPS domain into polar core, nonpolar core, and C-terminal subdomains. Moreover, the unfolding studies provide quantitative evidence that the folding free energy for the polar core subdomain is more favorable than for the nonpolar core and C-terminal subdomains. This study implicates the hydrogen bonds shared among these conserved internal residues as a primary means for stabilizing the N-proximal polar core subdomain.
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Affiliation(s)
- Megan R Wimmer
- Department of Chemistry and Biochemistry, University Wisconsin - La Crosse, La Crosse, Wisconsin, 54601
| | - Christopher N Woods
- Department of Chemistry and Biochemistry, University Wisconsin - La Crosse, La Crosse, Wisconsin, 54601
| | - Kyle J Adamczak
- Department of Chemistry and Biochemistry, University Wisconsin - La Crosse, La Crosse, Wisconsin, 54601
| | - Evan M Glasgow
- Department of Chemistry and Biochemistry, University Wisconsin - La Crosse, La Crosse, Wisconsin, 54601
| | - Walter R P Novak
- Department of Chemistry, Wabash College, Crawfordsville, Indiana, 47933
| | - Daniel P Grilley
- Department of Chemistry and Biochemistry, University Wisconsin - La Crosse, La Crosse, Wisconsin, 54601
| | - Todd M Weaver
- Department of Chemistry and Biochemistry, University Wisconsin - La Crosse, La Crosse, Wisconsin, 54601
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30
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Guérin J, Saint N, Baud C, Meli AC, Etienne E, Locht C, Vezin H, Jacob-Dubuisson F. Dynamic interplay of membrane-proximal POTRA domain and conserved loop L6 in Omp85 transporter FhaC. Mol Microbiol 2015; 98:490-501. [PMID: 26192332 DOI: 10.1111/mmi.13137] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/07/2015] [Indexed: 12/30/2022]
Abstract
Omp85 transporters mediate protein insertion into, or translocation across, membranes. They have a conserved architecture, with POTRA domains that interact with substrate proteins, a 16-stranded transmembrane β barrel, and an extracellular loop, L6, folded back in the barrel pore. Here using electrophysiology, in vivo biochemical approaches and electron paramagnetic resonance, we show that the L6 loop of the Omp85 transporter FhaC changes conformation and modulates channel opening. Those conformational changes involve breaking the conserved interaction between the tip of L6 and the inner β-barrel wall. The membrane-proximal POTRA domain also exchanges between several conformations, and the binding of FHA displaces this equilibrium. We further demonstrate a dynamic, physical communication between the POTRA domains and L6, which must take place via the β barrel. Our findings thus link all three essential components of Omp85 transporters and indicate that they operate in a concerted fashion in the transport cycle.
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Affiliation(s)
- Jeremy Guérin
- Institut Pasteur de Lille, CIIL, 1 rue Calmette, 59019, Lille Cedex, France.,Université de Lille, 1 rue G. Lefebvre, 59000, Lille, France.,CNRS UMR 8204, 2 rue des Canonniers, 59046, Lille, France.,INSERM U1019, 6 rue Pr. Laguesse, 59045, Lille, France
| | - Nathalie Saint
- PhyMedExp, University of Montpellier, INSERM U1046, CNRS UMR9214, 371 av. G. Giraud, 34295, Montpellier cedex 05, France
| | - Catherine Baud
- Institut Pasteur de Lille, CIIL, 1 rue Calmette, 59019, Lille Cedex, France.,Université de Lille, 1 rue G. Lefebvre, 59000, Lille, France.,CNRS UMR 8204, 2 rue des Canonniers, 59046, Lille, France.,INSERM U1019, 6 rue Pr. Laguesse, 59045, Lille, France
| | - Albano C Meli
- PhyMedExp, University of Montpellier, INSERM U1046, CNRS UMR9214, 371 av. G. Giraud, 34295, Montpellier cedex 05, France
| | - Emilien Etienne
- Aix-Marseille Université, CNRS, BIP (UMR 7281), 31 chemin J. Aiguier, 13402, Marseille cedex 20, France
| | - Camille Locht
- Institut Pasteur de Lille, CIIL, 1 rue Calmette, 59019, Lille Cedex, France.,Université de Lille, 1 rue G. Lefebvre, 59000, Lille, France.,CNRS UMR 8204, 2 rue des Canonniers, 59046, Lille, France.,INSERM U1019, 6 rue Pr. Laguesse, 59045, Lille, France
| | - Hervé Vezin
- Université de Lille, 1 rue G. Lefebvre, 59000, Lille, France.,CNRS UMR8516, Bat. C4, 59658, Villeneuve d'Ascq, France
| | - Françoise Jacob-Dubuisson
- Institut Pasteur de Lille, CIIL, 1 rue Calmette, 59019, Lille Cedex, France.,Université de Lille, 1 rue G. Lefebvre, 59000, Lille, France.,CNRS UMR 8204, 2 rue des Canonniers, 59046, Lille, France.,INSERM U1019, 6 rue Pr. Laguesse, 59045, Lille, France
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