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Schiffrin B, Crossley JA, Walko M, Machin JM, Nasir Khan G, Manfield IW, Wilson AJ, Brockwell DJ, Fessl T, Calabrese AN, Radford SE, Zhuravleva A. Dual client binding sites in the ATP-independent chaperone SurA. Nat Commun 2024; 15:8071. [PMID: 39277579 PMCID: PMC11401910 DOI: 10.1038/s41467-024-52021-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2024] [Accepted: 08/23/2024] [Indexed: 09/17/2024] Open
Abstract
The ATP-independent chaperone SurA protects unfolded outer membrane proteins (OMPs) from aggregation in the periplasm of Gram-negative bacteria, and delivers them to the β-barrel assembly machinery (BAM) for folding into the outer membrane (OM). Precisely how SurA recognises and binds its different OMP clients remains unclear. Escherichia coli SurA comprises three domains: a core and two PPIase domains (P1 and P2). Here, by combining methyl-TROSY NMR, single-molecule Förster resonance energy transfer (smFRET), and bioinformatics analyses we show that SurA client binding is mediated by two binding hotspots in the core and P1 domains. These interactions are driven by aromatic-rich motifs in the client proteins, leading to SurA core/P1 domain rearrangements and expansion of clients from collapsed, non-native states. We demonstrate that the core domain is key to OMP expansion by SurA, and uncover a role for SurA PPIase domains in limiting the extent of expansion. The results reveal insights into SurA-OMP recognition and the mechanism of activation for an ATP-independent chaperone, and suggest a route to targeting the functions of a chaperone key to bacterial virulence and OM integrity.
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Affiliation(s)
- Bob Schiffrin
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, UK
| | - Joel A Crossley
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, UK
| | - Martin Walko
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, UK
- Astbury Centre for Structural Molecular Biology, School of Chemistry, University of Leeds, Leeds, UK
| | - Jonathan M Machin
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, UK
| | - G Nasir Khan
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, UK
| | - Iain W Manfield
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, UK
| | - Andrew J Wilson
- Astbury Centre for Structural Molecular Biology, School of Chemistry, University of Leeds, Leeds, UK
- School of Chemistry, University of Birmingham, Edgbaston, Birmingham, UK
| | - David J Brockwell
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, UK
| | - Tomas Fessl
- Faculty of Science, University of South Bohemia, České Budějovice, Czech Republic
| | - Antonio N Calabrese
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, UK
| | - Sheena E Radford
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, UK.
| | - Anastasia Zhuravleva
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, UK.
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2
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Fenn KL, Horne JE, Crossley JA, Böhringer N, Horne RJ, Schäberle TF, Calabrese AN, Radford SE, Ranson NA. Outer membrane protein assembly mediated by BAM-SurA complexes. Nat Commun 2024; 15:7612. [PMID: 39218969 PMCID: PMC11366764 DOI: 10.1038/s41467-024-51358-x] [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: 04/11/2024] [Accepted: 08/02/2024] [Indexed: 09/04/2024] Open
Abstract
The outer membrane is a formidable barrier that protects Gram-negative bacteria against environmental threats. Its integrity requires the correct folding and insertion of outer membrane proteins (OMPs) by the membrane-embedded β-barrel assembly machinery (BAM). Unfolded OMPs are delivered to BAM by the periplasmic chaperone SurA, but how SurA and BAM work together to ensure successful OMP delivery and folding remains unclear. Here, guided by AlphaFold2 models, we use disulphide bond engineering in an attempt to trap SurA in the act of OMP delivery to BAM, and solve cryoEM structures of a series of complexes. The results suggest that SurA binds BAM at its soluble POTRA-1 domain, which may trigger conformational changes in both BAM and SurA that enable transfer of the unfolded OMP to the BAM lateral gate for insertion into the outer membrane. Mutations that disrupt the interaction between BAM and SurA result in outer membrane assembly defects, supporting the key role of SurA in outer membrane biogenesis.
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Affiliation(s)
- Katherine L Fenn
- Astbury Centre for Structural Molecular Biology and School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Jim E Horne
- Astbury Centre for Structural Molecular Biology and School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
- Department of Biochemistry, Tennis Court Road, Cambridge, CB2 1GA, UK
| | - Joel A Crossley
- Astbury Centre for Structural Molecular Biology and School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Nils Böhringer
- Institute for Insect Biotechnology, Justus-Liebig-University Giessen, 35392, Giessen, Germany
- German Center for Infection Research (DZIF), Partner Site Giessen-Marburg-Langen, 35392, Giessen, Germany
- Branch for Bioresources, Fraunhofer Institute for Molecular Biology and Applied Ecology (IME), 35392, Giessen, Germany
| | - Romany J Horne
- Astbury Centre for Structural Molecular Biology and School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
- Steinmetz Building, Granta Park, Great Abington, Cambridge, CB21 6DG, UK
| | - Till F Schäberle
- Institute for Insect Biotechnology, Justus-Liebig-University Giessen, 35392, Giessen, Germany
- German Center for Infection Research (DZIF), Partner Site Giessen-Marburg-Langen, 35392, Giessen, Germany
- Branch for Bioresources, Fraunhofer Institute for Molecular Biology and Applied Ecology (IME), 35392, Giessen, Germany
| | - Antonio N Calabrese
- Astbury Centre for Structural Molecular Biology and School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Sheena E Radford
- Astbury Centre for Structural Molecular Biology and School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK.
| | - Neil A Ranson
- Astbury Centre for Structural Molecular Biology and School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK.
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3
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Devlin T, Fleming KG. A team of chaperones play to win in the bacterial periplasm. Trends Biochem Sci 2024; 49:667-680. [PMID: 38677921 DOI: 10.1016/j.tibs.2024.03.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Revised: 03/14/2024] [Accepted: 03/22/2024] [Indexed: 04/29/2024]
Abstract
The survival and virulence of Gram-negative bacteria require proper biogenesis and maintenance of the outer membrane (OM), which is densely packed with β-barrel OM proteins (OMPs). Before reaching the OM, precursor unfolded OMPs (uOMPs) must cross the whole cell envelope. A network of periplasmic chaperones and proteases maintains unfolded but folding-competent conformations of these membrane proteins in the aqueous periplasm while simultaneously preventing off-pathway aggregation. These periplasmic proteins utilize different strategies, including conformational heterogeneity, oligomerization, multivalency, and kinetic partitioning, to perform and regulate their functions. Redundant and unique characteristics of the individual periplasmic players synergize to create a protein quality control team capable responding to changing environmental stresses.
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Affiliation(s)
- Taylor Devlin
- Thomas C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Karen G Fleming
- Thomas C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, MD 21218, USA.
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4
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Yarawsky AE, Dinu V, Harding SE, Herr AB. Strong non-ideality effects at low protein concentrations: considerations for elongated proteins. EUROPEAN BIOPHYSICS JOURNAL : EBJ 2023; 52:427-438. [PMID: 37055656 PMCID: PMC10599268 DOI: 10.1007/s00249-023-01648-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Revised: 03/17/2023] [Accepted: 03/29/2023] [Indexed: 04/15/2023]
Abstract
A recent investigation was aimed at obtaining structural information on a highly extended protein via SEC-MALS-SAXS. Significantly broadened elution peaks were observed, reminiscent of a phenomenon known as viscous fingering. This phenomenon is usually observed above 50 mg/mL for proteins like bovine serum albumin (BSA). Interestingly, the highly extended protein (Brpt5.5) showed viscous fingering at concentrations lower than 5 mg/mL. The current study explores this and other non-ideal behavior, emphasizing the presence of these effects at relatively low concentrations for extended proteins. BSA, Brpt5.5, and a truncated form of Brpt5.5 referred to as Brpt1.5 are studied systematically using size-exclusion chromatography (SEC), sedimentation velocity analytical ultracentrifugation (AUC), and viscosity. The viscous fingering effect is quantified using two approaches and is found to correlate well with the intrinsic viscosity of the proteins-Brpt5.5 exhibits the most severe effect and is the most extended protein tested in the study. By AUC, the hydrodynamic non-ideality was measured for each protein via global analysis of a concentration series. Compared to BSA, both Brpt1.5 and Brpt5.5 showed significant non-ideality that could be easily visualized at concentrations at or below 5 mg/mL and 1 mg/mL, respectively. A variety of relationships were examined for their ability to differentiate the proteins by shape using information from AUC and/or viscosity. Furthermore, these relationships were also tested in the context of hydrodynamic modeling. The importance of considering non-ideality when investigating the structure of extended macromolecules is discussed.
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Affiliation(s)
- Alexander E Yarawsky
- Division of Immunobiology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA.
- BioAnalysis, LLC, 3401 I Street Suite 206, Philadelphia, PA, 19134, USA.
| | - Vlad Dinu
- National Centre for Macromolecular Hydrodynamics (NCMH), University of Nottingham, Sutton Bonington, Loughborough, LE12 5RD, UK
| | - Stephen E Harding
- National Centre for Macromolecular Hydrodynamics (NCMH), University of Nottingham, Sutton Bonington, Loughborough, LE12 5RD, UK
| | - Andrew B Herr
- Division of Immunobiology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
- Division of Infectious Diseases, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
- Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH, USA
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5
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SurA-like and Skp-like Proteins as Important Virulence Determinants of the Gram Negative Bacterial Pathogens. Int J Mol Sci 2022; 24:ijms24010295. [PMID: 36613738 PMCID: PMC9820271 DOI: 10.3390/ijms24010295] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Revised: 12/19/2022] [Accepted: 12/20/2022] [Indexed: 12/28/2022] Open
Abstract
In the Gram-negative bacteria, many important virulence factors reach their destination via two-step export systems, and they must traverse the periplasmic space before reaching the outer membrane. Since these proteins must be maintained in a structure competent for transport into or across the membrane, they frequently require the assistance of chaperones. Based on the results obtained for the model bacterium Escherichia coli and related species, it is assumed that in the biogenesis of the outer membrane proteins and the periplasmic transit of secretory proteins, the SurA peptidyl-prolyl isomerase/chaperone plays a leading role, while the Skp chaperone is rather of secondary importance. However, detailed studies carried out on several other Gram-negative pathogens indicate that the importance of individual chaperones in the folding and transport processes depends on the properties of client proteins and is species-specific. Taking into account the importance of SurA functions in bacterial virulence and severity of phenotypes due to surA mutations, this folding factor is considered as a putative therapeutic target to combat microbial infections. In this review, we present recent findings regarding SurA and Skp proteins: their mechanisms of action, involvement in processes related to virulence, and perspectives to use them as therapeutic targets.
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6
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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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7
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Nussinov R, Zhang M, Maloney R, Tsai C, Yavuz BR, Tuncbag N, Jang H. Mechanism of activation and the rewired network: New drug design concepts. Med Res Rev 2022; 42:770-799. [PMID: 34693559 PMCID: PMC8837674 DOI: 10.1002/med.21863] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Revised: 07/06/2021] [Accepted: 10/07/2021] [Indexed: 12/13/2022]
Abstract
Precision oncology benefits from effective early phase drug discovery decisions. Recently, drugging inactive protein conformations has shown impressive successes, raising the cardinal questions of which targets can profit and what are the principles of the active/inactive protein pharmacology. Cancer driver mutations have been established to mimic the protein activation mechanism. We suggest that the decision whether to target an inactive (or active) conformation should largely rest on the protein mechanism of activation. We next discuss the recent identification of double (multiple) same-allele driver mutations and their impact on cell proliferation and suggest that like single driver mutations, double drivers also mimic the mechanism of activation. We further suggest that the structural perturbations of double (multiple) in cis mutations may reveal new surfaces/pockets for drug design. Finally, we underscore the preeminent role of the cellular network which is deregulated in cancer. Our structure-based review and outlook updates the traditional Mechanism of Action, informs decisions, and calls attention to the intrinsic activation mechanism of the target protein and the rewired tumor-specific network, ushering innovative considerations in precision medicine.
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Affiliation(s)
- Ruth Nussinov
- Computational Structural Biology Section, Frederick National Laboratory for Cancer Research in the Laboratory of Cancer ImmunometabolismNational Cancer InstituteFrederickMarylandUSA
- Department of Human Molecular Genetics and Biochemistry, Sackler School of MedicineTel Aviv UniversityTel AvivIsrael
| | - Mingzhen Zhang
- Computational Structural Biology Section, Frederick National Laboratory for Cancer Research in the Laboratory of Cancer ImmunometabolismNational Cancer InstituteFrederickMarylandUSA
| | - Ryan Maloney
- Computational Structural Biology Section, Frederick National Laboratory for Cancer Research in the Laboratory of Cancer ImmunometabolismNational Cancer InstituteFrederickMarylandUSA
| | - Chung‐Jung Tsai
- Computational Structural Biology Section, Frederick National Laboratory for Cancer Research in the Laboratory of Cancer ImmunometabolismNational Cancer InstituteFrederickMarylandUSA
| | - Bengi Ruken Yavuz
- Department of Health Informatics, Graduate School of InformaticsMiddle East Technical UniversityAnkaraTurkey
| | - Nurcan Tuncbag
- Department of Health Informatics, Graduate School of InformaticsMiddle East Technical UniversityAnkaraTurkey
- Department of Chemical and Biological Engineering, College of EngineeringKoc UniversityIstanbulTurkey
- Koc University Research Center for Translational Medicine, School of MedicineKoc UniversityIstanbulTurkey
| | - Hyunbum Jang
- Computational Structural Biology Section, Frederick National Laboratory for Cancer Research in the Laboratory of Cancer ImmunometabolismNational Cancer InstituteFrederickMarylandUSA
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8
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Sučec I, Bersch B, Schanda P. How do Chaperones Bind (Partly) Unfolded Client Proteins? Front Mol Biosci 2021; 8:762005. [PMID: 34760928 PMCID: PMC8573040 DOI: 10.3389/fmolb.2021.762005] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2021] [Accepted: 10/06/2021] [Indexed: 01/03/2023] Open
Abstract
Molecular chaperones are central to cellular protein homeostasis. Dynamic disorder is a key feature of the complexes of molecular chaperones and their client proteins, and it facilitates the client release towards a folded state or the handover to downstream components. The dynamic nature also implies that a given chaperone can interact with many different client proteins, based on physico-chemical sequence properties rather than on structural complementarity of their (folded) 3D structure. Yet, the balance between this promiscuity and some degree of client specificity is poorly understood. Here, we review recent atomic-level descriptions of chaperones with client proteins, including chaperones in complex with intrinsically disordered proteins, with membrane-protein precursors, or partially folded client proteins. We focus hereby on chaperone-client interactions that are independent of ATP. The picture emerging from these studies highlights the importance of dynamics in these complexes, whereby several interaction types, not only hydrophobic ones, contribute to the complex formation. We discuss these features of chaperone-client complexes and possible factors that may contribute to this balance of promiscuity and specificity.
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Affiliation(s)
- Iva Sučec
- CEA, CNRS, Institut de Biologie Structurale (IBS), Univ. Grenoble Alpes, Grenoble, France
| | - Beate Bersch
- CEA, CNRS, Institut de Biologie Structurale (IBS), Univ. Grenoble Alpes, Grenoble, France
| | - Paul Schanda
- CEA, CNRS, Institut de Biologie Structurale (IBS), Univ. Grenoble Alpes, Grenoble, France.,Institute of Science and Technology Austria, Klosterneuburg, Austria
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9
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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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10
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Marx DC, Plummer AM, Faustino AM, Devlin T, Roskopf MA, Leblanc MJ, Lessen HJ, Amann BT, Fleming PJ, Krueger S, Fried SD, Fleming KG. SurA is a cryptically grooved chaperone that expands unfolded outer membrane proteins. Proc Natl Acad Sci U S A 2020; 117:28026-28035. [PMID: 33093201 PMCID: PMC7668074 DOI: 10.1073/pnas.2008175117] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Accepted: 08/26/2020] [Indexed: 11/18/2022] Open
Abstract
The periplasmic chaperone network ensures the biogenesis of bacterial outer membrane proteins (OMPs) and has recently been identified as a promising target for antibiotics. SurA is the most important member of this network, both due to its genetic interaction with the β-barrel assembly machinery complex as well as its ability to prevent unfolded OMP (uOMP) aggregation. Using only binding energy, the mechanism by which SurA carries out these two functions is not well-understood. Here, we use a combination of photo-crosslinking, mass spectrometry, solution scattering, and molecular modeling techniques to elucidate the key structural features that define how SurA solubilizes uOMPs. Our experimental data support a model in which SurA binds uOMPs in a groove formed between the core and P1 domains. This binding event results in a drastic expansion of the rest of the uOMP, which has many biological implications. Using these experimental data as restraints, we adopted an integrative modeling approach to create a sparse ensemble of models of a SurA•uOMP complex. We validated key structural features of the SurA•uOMP ensemble using independent scattering and chemical crosslinking data. Our data suggest that SurA utilizes three distinct binding modes to interact with uOMPs and that more than one SurA can bind a uOMP at a time. This work demonstrates that SurA operates in a distinct fashion compared to other chaperones in the OMP biogenesis network.
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Affiliation(s)
- Dagan C Marx
- Thomas C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, MD 21218
| | - Ashlee M Plummer
- Thomas C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, MD 21218
| | | | - Taylor Devlin
- Thomas C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, MD 21218
| | - Michaela A Roskopf
- Thomas C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, MD 21218
| | - Mathis J Leblanc
- Thomas C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, MD 21218
| | - Henry J Lessen
- Thomas C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, MD 21218
| | - Barbara T Amann
- Thomas C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, MD 21218
| | - Patrick J Fleming
- Thomas C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, MD 21218
| | - Susan Krueger
- National Institute of Standards and Technology, Gaithersburg, MD 20899
| | - Stephen D Fried
- Department of Chemistry, Johns Hopkins University, Baltimore, MD 21218
| | - Karen G Fleming
- Thomas C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, MD 21218;
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11
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Marx DC, Leblanc MJ, Plummer AM, Krueger S, Fleming KG. Domain interactions determine the conformational ensemble of the periplasmic chaperone SurA. Protein Sci 2020; 29:2043-2053. [PMID: 32748422 PMCID: PMC7513704 DOI: 10.1002/pro.3924] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Revised: 07/31/2020] [Accepted: 07/31/2020] [Indexed: 12/17/2022]
Abstract
SurA is thought to be the most important periplasmic chaperone for outer membrane protein (OMP) biogenesis. Its structure is composed of a core region and two peptidylprolyl isomerase domains, termed P1 and P2, connected by flexible linkers. As such these three independent folding units are able to adopt a number of distinct spatial positions with respect to each other. The conformational dynamics of these domains are thought to be functionally important yet are largely unresolved. Here we address this question of the conformational ensemble using sedimentation equilibrium, small-angle neutron scattering, and folding titrations. This combination of orthogonal methods converges on a SurA population that is monomeric at physiological concentrations. The conformation that dominates this population has the P1 and core domains docked to one another, for example, "P1-closed" and the P2 domain extended in solution. We discovered that the distribution of domain orientations is defined by modest and favorable interactions between the core domain and either the P1 or the P2 domains. These two peptidylprolyl domains compete with each other for core-binding but are thermodynamically uncoupled. This arrangement implies two novel insights. Firstly, an open conformation must exist to facilitate P1 and P2 exchange on the core, indicating that the open client-binding conformation is populated at low levels even in the absence of client unfolded OMPs. Secondly, competition between P1 and P2 binding paradoxically occludes the client binding site on the core, which may serve to preserve the reservoir of binding-competent apo-SurA in the periplasm.
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Affiliation(s)
- Dagan C. Marx
- Thomas C. Jenkins Department of BiophysicsJohns Hopkins UniversityBaltimoreMarylandUSA
| | - Mathis J. Leblanc
- Thomas C. Jenkins Department of BiophysicsJohns Hopkins UniversityBaltimoreMarylandUSA
| | - Ashlee M. Plummer
- Thomas C. Jenkins Department of BiophysicsJohns Hopkins UniversityBaltimoreMarylandUSA
- Department of Cell BiologyHarvard Medical SchoolBostonMassachusettsUSA
| | - Susan Krueger
- National Institute of Standards and TechnologyGaithersburgMarylandUSA
| | - Karen G. Fleming
- Thomas C. Jenkins Department of BiophysicsJohns Hopkins UniversityBaltimoreMarylandUSA
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