1
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Schreiber S, Zaayenga A, Jose J. The Assembly of the Inverse Autotransporter Protein YeeJ is Driven by its C-terminal β-strand. J Mol Biol 2024; 436:168749. [PMID: 39173735 DOI: 10.1016/j.jmb.2024.168749] [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: 05/08/2024] [Revised: 08/16/2024] [Accepted: 08/17/2024] [Indexed: 08/24/2024]
Abstract
Autotransporter proteins are bacterial outer membrane proteins that display passenger domains with various functions through a β-barrel shaped translocation domain. YeeJ is an autotransporter protein from E. coli MG1655. In contrast to most other autotransporter proteins, its passenger domain is located at the C-terminus of the translocation domain. Due to this inverted domain organization, YeeJ belongs to autotransporter proteins of type Ve. To investigate the assembly of YeeJ, the fluorescence of a heterologous mCherry passenger domain was measured to quantify its assembly. Based on AlphaFold2 models of 119 sequences similar to YeeJ, a sequence conservation logo for the β1- and the β12-strand of type Ve autotransporter proteins was generated. Then, the effect of mutations in these strands on the assembly of YeeJ were analyzed. Mutations of the N-terminal aromatic amino acid of the β1-strand did not affect the assembly of the translocation domain and the display of the passenger domain. Likewise, exchange of the β1-strand with the β3-strand did not impair the assembly of the autotransporter fusion protein. Mutation of the C-terminal aromatic amino acid of the β12-strand strongly impaired surface display of the mCherry passenger domain. This amino acid has been shown before as an essential feature of the β-signals of classical autotransporter proteins and outer membrane β-barrel proteins in general. We therefore propose that the β12-strand of YeeJ acts as its β-signal and that the assembly of the YeeJ β-barrel is driven by its C-terminal β-strand, like in most other autotransporter proteins, despite its inverted domain organization.
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Affiliation(s)
- Sebastian Schreiber
- University of Münster, Institute of Pharmaceutical and Medicinal Chemistry, PharmaCampus, Corrensstr. 48, 48149 Münster, Germany
| | - Annika Zaayenga
- University of Münster, Institute of Pharmaceutical and Medicinal Chemistry, PharmaCampus, Corrensstr. 48, 48149 Münster, Germany
| | - Joachim Jose
- University of Münster, Institute of Pharmaceutical and Medicinal Chemistry, PharmaCampus, Corrensstr. 48, 48149 Münster, Germany.
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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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Wang X, Nyenhuis SB, Bernstein HD. The translocation assembly module (TAM) catalyzes the assembly of bacterial outer membrane proteins in vitro. Nat Commun 2024; 15:7246. [PMID: 39174534 PMCID: PMC11341756 DOI: 10.1038/s41467-024-51628-8] [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: 10/20/2023] [Accepted: 08/12/2024] [Indexed: 08/24/2024] Open
Abstract
The translocation and assembly module (TAM) has been proposed to play a crucial role in the assembly of a small subset of outer membrane proteins (OMPs) in Proteobacteria based on experiments conducted in vivo using tamA and tamB mutant strains and in vitro using biophysical methods. TAM consists of an OMP (TamA) and a periplasmic protein that is anchored to the inner membrane by a single α helix (TamB). Here we examine the function of the purified E. coli complex in vitro after reconstituting it into proteoliposomes. We find that TAM catalyzes the assembly of four model OMPs nearly as well as the β-barrel assembly machine (BAM), a universal heterooligomer that contains a TamA homolog (BamA) and that catalyzes the assembly of almost all E. coli OMPs. Consistent with previous results, both TamA and TamB are required for significant TAM activity. Our study provides direct evidence that TAM can function as an independent OMP insertase and describes a new method to gain insights into TAM function.
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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, MD, 20892, USA
| | - Sarah B Nyenhuis
- Laboratory of Cell and Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Harris D Bernstein
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, 20892, USA.
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4
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Hartojo A, Doyle MT. β-barrel membrane proteins fold via hybrid-barrel intermediate states. Curr Opin Struct Biol 2024; 87:102830. [PMID: 38728831 DOI: 10.1016/j.sbi.2024.102830] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2024] [Revised: 03/15/2024] [Accepted: 04/22/2024] [Indexed: 05/12/2024]
Abstract
Gram-negative bacteria and eukaryotic organelles of bacterial origin contain outer membrane proteins that possess a transmembrane "β-barrel" domain. The conserved β-barrel assembly machine (BAM) and the sorting and assembly machine (SAM) are required for the folding and membrane insertion of β-barrels in Gram-negative bacteria and mitochondria, respectively. Although the mechanisms by which β-barrels are folded are incompletely understood, advances in cryo-electron microscopy (cryo-EM) have recently yielded unprecedented insights into their folding process. Here we highlight recent studies that show that both bacterial and mitochondrial β-barrels fold via the formation of remarkable "hybrid-barrel" intermediate states during their interaction with the folding machinery. We discuss how these results align with a general model of β-barrel folding.
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Affiliation(s)
- Alfred Hartojo
- Sydney Infectious Diseases Institute, The University of Sydney, Darlington, New South Wales, Australia; School of Medical Sciences, Faculty of Medicine and Health, The University of Sydney, Darlington, New South Wales, Australia. https://twitter.com/AlfredHartojo29
| | - Matthew Thomas Doyle
- Sydney Infectious Diseases Institute, The University of Sydney, Darlington, New South Wales, Australia; School of Medical Sciences, Faculty of Medicine and Health, The University of Sydney, Darlington, New South Wales, Australia.
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5
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Gutishvili G, Yang L, Gumbart JC. Seeing is believing: Illuminating the Gram-negative outer membrane with molecular dynamics simulations. Curr Opin Struct Biol 2024; 87:102828. [PMID: 38723580 PMCID: PMC11283978 DOI: 10.1016/j.sbi.2024.102828] [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: 02/05/2024] [Revised: 04/14/2024] [Accepted: 04/15/2024] [Indexed: 07/29/2024]
Abstract
Recent advances in molecular dynamics (MD) simulations have led to rapid improvement in our understanding of the molecular details of the outer membranes (OMs) of Gram-negative bacteria. In this review, we highlight the latest discoveries from MD simulations of OMs, shedding light on the dynamic nature of these bacteria's first line of defense. With the focus on cutting-edge approaches, we explore the OM's sensitivity to structural features, including divalent cations and membrane composition, which have emerged as crucial determinants of antimicrobial passage. Additionally, studies have provided novel insights into outer-membrane proteins (OMPs), revealing their intricate roles in substrate translocation and their distinct interactions with lipopolysaccharides (LPS) in the OM. Finally, we explore the challenging process of β-barrel membrane protein insertion, showcasing recent findings that have enhanced our grasp of this fundamental biological phenomenon.
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Affiliation(s)
| | - Lixinhao Yang
- School of Chemistry and Biochemistry, 901 Atlantic Dr., Atlanta, GA, 30332, USA
| | - James C Gumbart
- School of Physics, 837 State St., Atlanta, GA, 30332, USA; School of Chemistry and Biochemistry, 901 Atlantic Dr., Atlanta, GA, 30332, USA.
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6
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Modak A, Kilic Z, Chattrakun K, Terry DS, Kalathur RC, Blanchard SC. Single-Molecule Imaging of Integral Membrane Protein Dynamics and Function. Annu Rev Biophys 2024; 53:427-453. [PMID: 39013028 DOI: 10.1146/annurev-biophys-070323-024308] [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] [Indexed: 07/18/2024]
Abstract
Integral membrane proteins (IMPs) play central roles in cellular physiology and represent the majority of known drug targets. Single-molecule fluorescence and fluorescence resonance energy transfer (FRET) methods have recently emerged as valuable tools for investigating structure-function relationships in IMPs. This review focuses on the practical foundations required for examining polytopic IMP function using single-molecule FRET (smFRET) and provides an overview of the technical and conceptual frameworks emerging from this area of investigation. In this context, we highlight the utility of smFRET methods to reveal transient conformational states critical to IMP function and the use of smFRET data to guide structural and drug mechanism-of-action investigations. We also identify frontiers where progress is likely to be paramount to advancing the field.
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Affiliation(s)
- Arnab Modak
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, Tennessee, USA; , , , , ,
| | - Zeliha Kilic
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, Tennessee, USA; , , , , ,
| | - Kanokporn Chattrakun
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, Tennessee, USA; , , , , ,
| | - Daniel S Terry
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, Tennessee, USA; , , , , ,
| | - Ravi C Kalathur
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, Tennessee, USA; , , , , ,
| | - Scott C Blanchard
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, Tennessee, USA; , , , , ,
- Department of Chemical Biology & Therapeutics, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
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7
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Goh KJ, Stubenrauch CJ, Lithgow T. The TAM, a Translocation and Assembly Module for protein assembly and potential conduit for phospholipid transfer. EMBO Rep 2024; 25:1711-1720. [PMID: 38467907 PMCID: PMC11014939 DOI: 10.1038/s44319-024-00111-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Revised: 02/08/2024] [Accepted: 02/20/2024] [Indexed: 03/13/2024] Open
Abstract
The assembly of β-barrel proteins into the bacterial outer membrane is an essential process enabling the colonization of new environmental niches. The TAM was discovered as a module of the β-barrel protein assembly machinery; it is a heterodimeric complex composed of an outer membrane protein (TamA) bound to an inner membrane protein (TamB). The TAM spans the periplasm, providing a scaffold through the peptidoglycan layer and catalyzing the translocation and assembly of β-barrel proteins into the outer membrane. Recently, studies on another membrane protein (YhdP) have suggested that TamB might play a role in phospholipid transport to the outer membrane. Here we review and re-evaluate the literature covering the experimental studies on the TAM over the past decade, to reconcile what appear to be conflicting claims on the function of the TAM.
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Affiliation(s)
- Kwok Jian Goh
- Centre to Impact AMR, Monash University, Melbourne, VIC, 3800, Australia
- Infection Program, Biomedicine Discovery Institute and Department of Microbiology, Monash University, Melbourne, VIC, 3800, Australia
| | - Christopher J Stubenrauch
- Centre to Impact AMR, Monash University, Melbourne, VIC, 3800, Australia
- Infection Program, Biomedicine Discovery Institute and Department of Microbiology, Monash University, Melbourne, VIC, 3800, Australia
| | - Trevor Lithgow
- Centre to Impact AMR, Monash University, Melbourne, VIC, 3800, Australia.
- Infection Program, Biomedicine Discovery Institute and Department of Microbiology, Monash University, Melbourne, VIC, 3800, Australia.
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8
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Badten AJ, Torres AG. Burkholderia pseudomallei Complex Subunit and Glycoconjugate Vaccines and Their Potential to Elicit Cross-Protection to Burkholderia cepacia Complex. Vaccines (Basel) 2024; 12:313. [PMID: 38543947 PMCID: PMC10975474 DOI: 10.3390/vaccines12030313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2024] [Revised: 03/12/2024] [Accepted: 03/14/2024] [Indexed: 04/01/2024] Open
Abstract
Burkholderia are a group of Gram-negative bacteria that can cause a variety of diseases in at-risk populations. B. pseudomallei and B. mallei, the etiological agents of melioidosis and glanders, respectively, are the two clinically relevant members of the B. pseudomallei complex (Bpc). The development of vaccines against Bpc species has been accelerated in recent years, resulting in numerous promising subunits and glycoconjugate vaccines incorporating a variety of antigens. However, a second group of pathogenic Burkholderia species exists known as the Burkholderia cepacia complex (Bcc), a group of opportunistic bacteria which tend to affect individuals with weakened immunity or cystic fibrosis. To date, there have been few attempts to develop vaccines to Bcc species. Therefore, the primary goal of this review is to provide a broad overview of the various subunit antigens that have been tested in Bpc species, their protective efficacy, study limitations, and known or suspected mechanisms of protection. Then, we assess the reviewed Bpc antigens for their amino acid sequence conservation to homologous proteins found in Bcc species. We propose that protective Bpc antigens with a high degree of Bpc-to-Bcc sequence conservation could serve as components of a pan-Burkholderia vaccine capable of protecting against both disease-causing groups.
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Affiliation(s)
- Alexander J. Badten
- Department of Microbiology & Immunology, University of Texas Medical Branch, Galveston, TX 77555, USA;
- Institute for Translational Sciences, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Alfredo G. Torres
- Department of Microbiology & Immunology, University of Texas Medical Branch, Galveston, TX 77555, USA;
- Department of Pathology, University of Texas Medical Branch, Galveston, TX 77555, USA
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9
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George A, Patil AG, Mahalakshmi R. ATP-independent assembly machinery of bacterial outer membranes: BAM complex structure and function set the stage for next-generation therapeutics. Protein Sci 2024; 33:e4896. [PMID: 38284489 PMCID: PMC10804688 DOI: 10.1002/pro.4896] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Revised: 12/28/2023] [Accepted: 12/31/2023] [Indexed: 01/30/2024]
Abstract
Diderm bacteria employ β-barrel outer membrane proteins (OMPs) as their first line of communication with their environment. These OMPs are assembled efficiently in the asymmetric outer membrane by the β-Barrel Assembly Machinery (BAM). The multi-subunit BAM complex comprises the transmembrane OMP BamA as its functional subunit, with associated lipoproteins (e.g., BamB/C/D/E/F, RmpM) varying across phyla and performing different regulatory roles. The ability of BAM complex to recognize and fold OM β-barrels of diverse sizes, and reproducibly execute their membrane insertion, is independent of electrochemical energy. Recent atomic structures, which captured BAM-substrate complexes, show the assembly function of BamA can be tailored, with different substrate types exhibiting different folding mechanisms. Here, we highlight common and unique features of its interactome. We discuss how this conserved protein complex has evolved the ability to effectively achieve the directed assembly of diverse OMPs of wide-ranging sizes (8-36 β-stranded monomers). Additionally, we discuss how darobactin-the first natural membrane protein inhibitor of Gram-negative bacteria identified in over five decades-selectively targets and specifically inhibits BamA. We conclude by deliberating how a detailed deduction of BAM complex-associated regulation of OMP biogenesis and OM remodeling will open avenues for the identification and development of effective next-generation therapeutics against Gram-negative pathogens.
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Affiliation(s)
- Anjana George
- Molecular Biophysics Laboratory, Department of Biological SciencesIndian Institute of Science Education and ResearchBhopalIndia
| | - Akanksha Gajanan Patil
- Molecular Biophysics Laboratory, Department of Biological SciencesIndian Institute of Science Education and ResearchBhopalIndia
| | - Radhakrishnan Mahalakshmi
- Molecular Biophysics Laboratory, Department of Biological SciencesIndian Institute of Science Education and ResearchBhopalIndia
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10
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Storek KM, Sun D, Rutherford ST. Inhibitors targeting BamA in gram-negative bacteria. BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH 2024; 1871:119609. [PMID: 37852326 DOI: 10.1016/j.bbamcr.2023.119609] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2022] [Revised: 06/08/2023] [Accepted: 09/19/2023] [Indexed: 10/20/2023]
Abstract
Antibiotic resistance has led to an increase in the number of patient hospitalizations and deaths. The situation for gram-negative bacteria is especially dire as the last new class of antibiotics active against these bacteria was introduced to the clinic over 60 years ago, thus there is an immediate unmet need for new antibiotic classes able to overcome resistance. The outer membrane, a unique and essential structure in gram-negative bacteria, contains multiple potential antibacterial targets including BamA, an outer membrane protein that folds and inserts transmembrane β-barrel proteins. BamA is essential and conserved, and its outer membrane location eliminates a barrier that molecules must overcome to access this target. Recently, antibacterial small molecules, natural products, peptides, and antibodies that inhibit BamA activity have been reported, validating the druggability of this target and generating potential leads for antibiotic development. This review will describe these BamA inhibitors, highlight their key attributes, and identify challenges with this potential target.
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Affiliation(s)
- Kelly M Storek
- Department of Infectious Diseases, Genentech Inc., South San Francisco, CA, USA
| | - Dawei Sun
- Department of Structural Biology, Genentech Inc., South San Francisco, CA, USA
| | - Steven T Rutherford
- Department of Infectious Diseases, Genentech Inc., South San Francisco, CA, USA.
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11
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Rath P, Hermann A, Schaefer R, Agustoni E, Vonach JM, Siegrist M, Miscenic C, Tschumi A, Roth D, Bieniossek C, Hiller S. High-throughput screening of BAM inhibitors in native membrane environment. Nat Commun 2023; 14:5648. [PMID: 37704632 PMCID: PMC10499997 DOI: 10.1038/s41467-023-41445-w] [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: 04/02/2022] [Accepted: 09/02/2023] [Indexed: 09/15/2023] Open
Abstract
The outer membrane insertase of Gram-negative bacteria, BAM, is a key target for urgently needed novel antibiotics. Functional reconstitutions of BAM have so far been limited to synthetic membranes and with low throughput capacity for inhibitor screening. Here, we describe a BAM functional assay in native membrane environment capable of high-throughput screening. This is achieved by employing outer membrane vesicles (OMVs) to present BAM directly in native membranes. Refolding of the model substrate OmpT by BAM was possible from the chaperones SurA and Skp, with the required SurA concentration three times higher than Skp. In the OMVs, the antibiotic darobactin had a tenfold higher potency than in synthetic membranes, highlighting the need for native conditions in antibiotics development. The assay is successfully miniaturized for 1536-well plates and upscaled using large scale fermentation, resulting in high-throughput capacities to screen large commercial compound libraries. Our OMV-based assay thus lays the basis for discovery, hit validation and lead expansion of antibiotics targeting BAM.
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Affiliation(s)
- Parthasarathi Rath
- Biozentrum, University of Basel, Spitalstrasse 41, 4056, Basel, Switzerland
| | - Adrian Hermann
- Roche Pharma Research and Early Development, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd, Grenzacherstrasse 124, 4070, Basel, Switzerland
| | - Ramona Schaefer
- Roche Pharma Research and Early Development, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd, Grenzacherstrasse 124, 4070, Basel, Switzerland
| | - Elia Agustoni
- Biozentrum, University of Basel, Spitalstrasse 41, 4056, Basel, Switzerland
| | - Jean-Marie Vonach
- Roche Pharma Research and Early Development, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd, Grenzacherstrasse 124, 4070, Basel, Switzerland
| | - Martin Siegrist
- Roche Pharma Research and Early Development, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd, Grenzacherstrasse 124, 4070, Basel, Switzerland
| | - Christian Miscenic
- Roche Pharma Research and Early Development, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd, Grenzacherstrasse 124, 4070, Basel, Switzerland
| | - Andreas Tschumi
- Roche Pharma Research and Early Development, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd, Grenzacherstrasse 124, 4070, Basel, Switzerland
| | - Doris Roth
- Roche Pharma Research and Early Development, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd, Grenzacherstrasse 124, 4070, Basel, Switzerland
| | - Christoph Bieniossek
- Roche Pharma Research and Early Development, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd, Grenzacherstrasse 124, 4070, Basel, Switzerland.
| | - Sebastian Hiller
- Biozentrum, University of Basel, Spitalstrasse 41, 4056, Basel, Switzerland.
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12
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Overduin M, Kervin TA, Klarenbach Z, Adra TRC, Bhat RK. Comprehensive classification of proteins based on structures that engage lipids by COMPOSEL. Biophys Chem 2023; 295:106971. [PMID: 36801589 DOI: 10.1016/j.bpc.2023.106971] [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: 12/24/2022] [Accepted: 02/05/2023] [Indexed: 02/11/2023]
Abstract
Structures can now be predicted for any protein using programs like AlphaFold and Rosetta, which rely on a foundation of experimentally determined structures of architecturally diverse proteins. The accuracy of such artificial intelligence and machine learning (AI/ML) approaches benefits from the specification of restraints which assist in navigating the universe of folds to converge on models most representative of a given protein's physiological structure. This is especially pertinent for membrane proteins, with structures and functions that depend on their presence in lipid bilayers. Structures of proteins in their membrane environments could conceivably be predicted from AI/ML approaches with user-specificized parameters that describe each element of the architecture of a membrane protein accompanied by its lipid environment. We propose the Classification Of Membrane Proteins based On Structures Engaging Lipids (COMPOSEL), which builds on existing nomenclature types for monotopic, bitopic, polytopic and peripheral membrane proteins as well as lipids. Functional and regulatory elements are also defined in the scripts, as shown with membrane fusing synaptotagmins, multidomain PDZD8 and Protrudin proteins that recognize phosphoinositide (PI) lipids, the intrinsically disordered MARCKS protein, caveolins, the β barrel assembly machine (BAM), an adhesion G-protein coupled receptor (aGPCR) and two lipid modifying enzymes - diacylglycerol kinase DGKε and fatty aldehyde dehydrogenase FALDH. This demonstrates how COMPOSEL communicates lipid interactivity as well as signaling mechanisms and binding of metabolites, drug molecules, polypeptides or nucleic acids to describe the operations of any protein. Moreover COMPOSEL can be scaled to express how genomes encode membrane structures and how our organs are infiltrated by pathogens such as SARS-CoV-2.
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Affiliation(s)
- Michael Overduin
- Department of Biochemistry, University of Alberta, Edmonton, AB, Canada.
| | - Troy A Kervin
- Department of Biochemistry, University of Alberta, Edmonton, AB, Canada
| | | | - Trixie Rae C Adra
- Department of Biochemistry, University of Alberta, Edmonton, AB, Canada
| | - Rakesh K Bhat
- Department of Biochemistry, University of Alberta, Edmonton, AB, Canada
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13
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Overly Cottom C, Stephenson R, Wilson L, Noinaj N. Targeting BAM for Novel Therapeutics against Pathogenic Gram-Negative Bacteria. Antibiotics (Basel) 2023; 12:679. [PMID: 37107041 PMCID: PMC10135246 DOI: 10.3390/antibiotics12040679] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Revised: 02/28/2023] [Accepted: 03/06/2023] [Indexed: 04/29/2023] Open
Abstract
The growing emergence of multidrug resistance in bacterial pathogens is an immediate threat to human health worldwide. Unfortunately, there has not been a matching increase in the discovery of new antibiotics to combat this alarming trend. Novel contemporary approaches aimed at antibiotic discovery against Gram-negative bacterial pathogens have expanded focus to also include essential surface-exposed receptors and protein complexes, which have classically been targeted for vaccine development. One surface-exposed protein complex that has gained recent attention is the β-barrel assembly machinery (BAM), which is conserved and essential across all Gram-negative bacteria. BAM is responsible for the biogenesis of β-barrel outer membrane proteins (β-OMPs) into the outer membrane. These β-OMPs serve essential roles for the cell including nutrient uptake, signaling, and adhesion, but can also serve as virulence factors mediating pathogenesis. The mechanism for how BAM mediates β-OMP biogenesis is known to be dynamic and complex, offering multiple modes for inhibition by small molecules and targeting by larger biologics. In this review, we introduce BAM and establish why it is a promising and exciting new therapeutic target and present recent studies reporting novel compounds and vaccines targeting BAM across various bacteria. These reports have fueled ongoing and future research on BAM and have boosted interest in BAM for its therapeutic promise in combatting multidrug resistance in Gram-negative bacterial pathogens.
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Affiliation(s)
- Claire Overly Cottom
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA
| | - Robert Stephenson
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA
| | - Lindsey Wilson
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA
| | - Nicholas Noinaj
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA
- Markey Center for Structural Biology, Purdue University, West Lafayette, IN 47907, USA
- Purdue Institute of Inflammation, Immunology and Infectious Disease, Purdue University, West Lafayette, IN 47907, USA
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14
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Surveying membrane landscapes: a new look at the bacterial cell surface. Nat Rev Microbiol 2023:10.1038/s41579-023-00862-w. [PMID: 36828896 DOI: 10.1038/s41579-023-00862-w] [Citation(s) in RCA: 14] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/30/2023] [Indexed: 02/26/2023]
Abstract
Recent studies applying advanced imaging techniques are changing the way we understand bacterial cell surfaces, bringing new knowledge on everything from single-cell heterogeneity in bacterial populations to their drug sensitivity and mechanisms of antimicrobial resistance. In both Gram-positive and Gram-negative bacteria, the outermost surface of the bacterial cell is being imaged at nanoscale; as a result, topographical maps of bacterial cell surfaces can be constructed, revealing distinct zones and specific features that might uniquely identify each cell in a population. Functionally defined assembly precincts for protein insertion into the membrane have been mapped at nanoscale, and equivalent lipid-assembly precincts are suggested from discrete lipopolysaccharide patches. As we review here, particularly for Gram-negative bacteria, the applications of various modalities of nanoscale imaging are reawakening our curiosity about what is conceptually a 3D cell surface landscape: what it looks like, how it is made and how it provides resilience to respond to environmental impacts.
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15
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Brodsky JL, Engelman DM, Hendershot LM, Piana-Agostinetti S, Sommer T. Taking out the trash: How misfolded proteins are removed from the endoplasmic reticulum. Fac Rev 2022; 11:29. [PMID: 36267301 PMCID: PMC9554898 DOI: 10.12703/r-01-0000018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/22/2023] Open
Abstract
Proteins that are expressed on membrane surfaces or secreted are involved in all aspects of cellular and organismal life, and as such require extremely high fidelity during their synthesis and maturation. These proteins are synthesized at the endoplasmic reticulum (ER) where a dedicated quality control system (ERQC) ensures only properly matured proteins reach their destinations. An essential component of this process is the identification of proteins that fail to pass ERQC and their retrotranslocation to the cytosol for proteasomal degradation. This study by Wu et al. reports a cryo-electron microscopy (cryo-EM) structure of the five-protein channel through which aberrant proteins are extracted from the ER, providing insights into how recognition of misfolded proteins is coupled to their transport through a hydrophobic channel that acts to thin the ER membrane, further facilitating their dislocation to the cytosol1.
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16
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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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17
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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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18
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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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19
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Hao B, Zhou W, Theg SM. Hydrophobic mismatch is a key factor in protein transport across lipid bilayer membranes via the Tat pathway. J Biol Chem 2022; 298:101991. [PMID: 35490783 PMCID: PMC9207671 DOI: 10.1016/j.jbc.2022.101991] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Revised: 04/13/2022] [Accepted: 04/19/2022] [Indexed: 11/28/2022] Open
Abstract
The twin-arginine translocation (Tat) pathway transports folded proteins across membranes in bacteria, thylakoids, plant mitochondria, and archaea. In most species, the active Tat machinery consists of three independent subunits: TatA, TatB, and TatC. TatA and TatB possess short transmembrane alpha helices (TMHs), both of which are only 15 residues long in Escherichia coli. Such short TMHs cause a hydrophobic mismatch between Tat subunits and the membrane bilayer, although the functional significance of this mismatch is unclear. Here, we sought to address the functional importance of the hydrophobic mismatch in the Tat transport mechanism in E. coli. We conducted three different assays to evaluate the effect of TMH length mutants on Tat activity and observed that the TMHs of TatA and TatB appear to be evolutionarily tuned to 15 amino acids, with activity dropping off following any modification of this length. Surprisingly, TatA and TatB with as few as 11 residues in their TMHs can still insert into the membrane bilayer, albeit with a decline in membrane integrity. These findings support a model of Tat transport utilizing localized toroidal pores that form when the membrane bilayer is thinned to a critical threshold. In this context, we conclude that the 15-residue length of the TatA and TatB TMHs can be seen as a compromise between the need for some hydrophobic mismatch to allow the membrane to reversibly reach the threshold thinness required for toroidal pore formation and the permanently destabilizing effect of placing even shorter helices into these energy-transducing membranes.
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Affiliation(s)
- Binhan Hao
- Plant Biology Department, University of California, Davis, CA 95616
| | - Wenjie Zhou
- Plant Biology Department, University of California, Davis, CA 95616
| | - Steven M Theg
- Plant Biology Department, University of California, Davis, CA 95616.
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20
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Doyle MT, Jimah JR, Dowdy T, Ohlemacher SI, Larion M, Hinshaw JE, Bernstein HD. Cryo-EM structures reveal multiple stages of bacterial outer membrane protein folding. Cell 2022; 185:1143-1156.e13. [PMID: 35294859 DOI: 10.1016/j.cell.2022.02.016] [Citation(s) in RCA: 41] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2021] [Revised: 12/01/2021] [Accepted: 02/13/2022] [Indexed: 02/08/2023]
Abstract
Transmembrane β barrel proteins are folded into the outer membrane (OM) of Gram-negative bacteria by the β barrel assembly machinery (BAM) via a poorly understood process that occurs without known external energy sources. Here, we used single-particle cryo-EM to visualize the folding dynamics of a model β barrel protein (EspP) by BAM. We found that BAM binds the highly conserved "β signal" motif of EspP to correctly orient β strands in the OM during folding. We also found that the folding of EspP proceeds via "hybrid-barrel" intermediates in which membrane integrated β sheets are attached to the essential BAM subunit, BamA. The structures show an unprecedented deflection of the membrane surrounding the EspP intermediates and suggest that β sheets progressively fold toward BamA to form a β barrel. Along with in vivo experiments that tracked β barrel folding while the OM tension was modified, our results support a model in which BAM harnesses OM elasticity to accelerate β barrel folding.
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Affiliation(s)
- Matthew Thomas Doyle
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - John R Jimah
- Laboratory of Cell and Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Tyrone Dowdy
- Neuro-Oncology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Shannon I Ohlemacher
- Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Mioara Larion
- Neuro-Oncology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Jenny E Hinshaw
- Laboratory of Cell and Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
| | - Harris D Bernstein
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
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21
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Horne JE, Radford SE. Roll out the barrel! Outer membrane tension resolves an unexpected folding intermediate. Cell 2022; 185:1107-1109. [DOI: 10.1016/j.cell.2022.03.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2022] [Revised: 02/25/2022] [Accepted: 02/28/2022] [Indexed: 12/01/2022]
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22
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Gopinath A, Joseph B. Conformational Flexibility of the Protein Insertase BamA in the Native Asymmetric Bilayer Elucidated by ESR Spectroscopy. Angew Chem Int Ed Engl 2022; 61:e202113448. [PMID: 34761852 PMCID: PMC9299766 DOI: 10.1002/anie.202113448] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2021] [Indexed: 12/15/2022]
Abstract
The β-barrel assembly machinery (BAM) consisting of the central β-barrel BamA and four other lipoproteins mediates the folding of the majority of the outer membrane proteins. BamA is placed in an asymmetric bilayer and its lateral gate is suggested to be the functional hotspot. Here we used in situ pulsed electron-electron double resonance spectroscopy to characterize BamA in the native outer membrane. In the detergent micelles, the data is consistent with mainly an inward-open conformation of BamA. The native membrane considerably enhanced the conformational heterogeneity. The lateral gate and the extracellular loop 3 exist in an equilibrium between different conformations. The outer membrane provides a favorable environment for occupying multiple conformational states independent of the lipoproteins. Our results reveal a highly dynamic behavior of the lateral gate and other key structural elements and provide direct evidence for the conformational modulation of a membrane protein in situ.
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Affiliation(s)
- Aathira Gopinath
- Institute of BiophysicsDepartment of PhysicsCenter for Biomolecular Magnetic Resonance (BMRZ)Goethe University FrankfurtMax-von-Laue-Str. 160438Frankfurt/MainGermany
| | - Benesh Joseph
- Institute of BiophysicsDepartment of PhysicsCenter for Biomolecular Magnetic Resonance (BMRZ)Goethe University FrankfurtMax-von-Laue-Str. 160438Frankfurt/MainGermany
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23
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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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24
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Gopinath A, Joseph B. Conformational Flexibility of the Protein Insertase BamA in the Native Asymmetric Bilayer Elucidated by ESR Spectroscopy. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202113448] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Aathira Gopinath
- Institute of Biophysics Department of Physics Center for Biomolecular Magnetic Resonance (BMRZ) Goethe University Frankfurt Max-von-Laue-Str. 1 60438 Frankfurt/Main Germany
| | - Benesh Joseph
- Institute of Biophysics Department of Physics Center for Biomolecular Magnetic Resonance (BMRZ) Goethe University Frankfurt Max-von-Laue-Str. 1 60438 Frankfurt/Main Germany
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25
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Thoma J, Burmann BM. Architects of their own environment: How membrane proteins shape the Gram-negative cell envelope. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2021; 128:1-34. [PMID: 35034716 DOI: 10.1016/bs.apcsb.2021.10.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Gram-negative bacteria are surrounded by a complex multilayered cell envelope, consisting of an inner and an outer membrane, and separated by the aqueous periplasm, which contains a thin peptidoglycan cell wall. These bacteria employ an arsenal of highly specialized membrane protein machineries to ensure the correct assembly and maintenance of the membranes forming the cell envelope. Here, we review the diverse protein systems, which perform these functions in Escherichia coli, such as the folding and insertion of membrane proteins, the transport of lipoproteins and lipopolysaccharide within the cell envelope, the targeting of phospholipids, and the regulation of mistargeted envelope components. Some of these protein machineries have been known for a long time, yet still hold surprises. Others have only recently been described and some are still missing pieces or yet remain to be discovered.
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Affiliation(s)
- Johannes Thoma
- Wallenberg Centre for Molecular and Translational Medicine, University of Gothenburg, Göteborg, Sweden; Department of Chemistry and Molecular Biology, University of Gothenburg, Göteborg, Sweden.
| | - Björn M Burmann
- Wallenberg Centre for Molecular and Translational Medicine, University of Gothenburg, Göteborg, Sweden; Department of Chemistry and Molecular Biology, University of Gothenburg, Göteborg, Sweden
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26
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Abstract
Membrane proteins (MPs) play essential roles in numerous cellular processes. Because around 70% of the currently marketed drugs target MPs, a detailed understanding of their structure, binding properties, and functional dynamics in a physiologically relevant environment is crucial for a more detailed understanding of this important protein class. We here summarize the benefits of using lipid nanodiscs for NMR structural investigations and provide a detailed overview of the currently used lipid nanodisc systems as well as their applications in solution-state NMR. Despite the increasing use of other structural methods for the structure determination of MPs in lipid nanodiscs, solution NMR turns out to be a versatile tool to probe a wide range of MP features, ranging from the structure determination of small to medium-sized MPs to probing ligand and partner protein binding as well as functionally relevant dynamical signatures in a lipid nanodisc setting. We will expand on these topics by discussing recent NMR studies with lipid nanodiscs and work out a key workflow for optimizing the nanodisc incorporation of an MP for subsequent NMR investigations. With this, we hope to provide a comprehensive background to enable an informed assessment of the applicability of lipid nanodiscs for NMR studies of a particular MP of interest.
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Affiliation(s)
- Umut Günsel
- Bavarian NMR Center (BNMRZ) at the Department of Chemistry, Technical University of Munich, Ernst-Otto-Fischer-Strasse 2, 85748 Garching, Germany
| | - Franz Hagn
- Bavarian NMR Center (BNMRZ) at the Department of Chemistry, Technical University of Munich, Ernst-Otto-Fischer-Strasse 2, 85748 Garching, Germany.,Institute of Structural Biology, Helmholtz Zentrum München, Ingolstädter Landstraße 1, 85764 Neuherberg, Germany
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27
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Curley CL, Fedrigoni TP, Flaherty EM, Woodilla CJ, Hagan CL. Bacterial Contact-Dependent Inhibition Protein Binds near the Open Lateral Gate in BamA Prior to Toxin Translocation. Biochemistry 2021; 60:2956-2965. [PMID: 34541845 DOI: 10.1021/acs.biochem.1c00337] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Contact-dependent inhibition (CDI) is a mechanism of interbacterial competition in Gram-negative bacteria. The critical component of CDI systems is a large protein named CdiA; it forms a filament on the bacterial cell surface and contains a toxin domain at its C-terminal end. Upon binding to a receptor protein on the surface of a neighboring cell, CdiA delivers the toxin domain through the outer membrane of the neighboring bacterium. The mechanism of that delivery process is poorly understood. We have characterized how CdiA from E. coli EC93 binds to its receptor, BamA, to understand how this binding event might initiate the process of toxin delivery. BamA is an essential protein that assembles β-barrel proteins into the outer membranes of all Gram-negative bacteria; this assembly process depends on BamA's unique ability to open laterally in the lipid bilayer through a gate in its own membrane-embedded β-barrel. Through site-specific photo-cross-linking and mutational analysis, we demonstrate that the BamA-CdiA interaction depends on a small number of non-conserved amino acids on the extracellular surface of BamA, but the protein interface extends over a region near BamA's lateral gate. We further demonstrate that BamA's lateral gate can open without disrupting the interaction with CdiA. CdiA thus appears to initially engage BamA in a manner that could allow it to utilize BamA's lateral gate in subsequent steps in the toxin translocation process.
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Affiliation(s)
- Cameron L Curley
- Department of Chemistry, The College of the Holy Cross, Worcester, Massachusetts 01610, United States
| | - Thomas P Fedrigoni
- Department of Chemistry, The College of the Holy Cross, Worcester, Massachusetts 01610, United States
| | - Erin M Flaherty
- Department of Chemistry, The College of the Holy Cross, Worcester, Massachusetts 01610, United States
| | - Christopher J Woodilla
- Department of Chemistry, The College of the Holy Cross, Worcester, Massachusetts 01610, United States
| | - Christine L Hagan
- Department of Chemistry, The College of the Holy Cross, Worcester, Massachusetts 01610, United States
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28
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Insights into the bilayer-mediated toppling mechanism of a folate-specific ECF transporter by cryo-EM. Proc Natl Acad Sci U S A 2021; 118:2105014118. [PMID: 34408021 DOI: 10.1073/pnas.2105014118] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Energy-coupling factor (ECF)-type transporters are small, asymmetric membrane protein complexes (∼115 kDa) that consist of a membrane-embedded, substrate-binding protein (S component) and a tripartite ATP-hydrolyzing module (ECF module). They import micronutrients into bacterial cells and have been proposed to use a highly unusual transport mechanism, in which the substrate is dragged across the membrane by a toppling motion of the S component. However, it remains unclear how the lipid bilayer could accommodate such a movement. Here, we used cryogenic electron microscopy at 200 kV to determine structures of a folate-specific ECF transporter in lipid nanodiscs and detergent micelles at 2.7- and 3.4-Å resolution, respectively. The structures reveal an irregularly shaped bilayer environment around the membrane-embedded complex and suggest that toppling of the S component is facilitated by protein-induced membrane deformations. In this way, structural remodeling of the lipid bilayer environment is exploited to guide the transport process.
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The role of membrane destabilisation and protein dynamics in BAM catalysed OMP folding. Nat Commun 2021; 12:4174. [PMID: 34234105 PMCID: PMC8263589 DOI: 10.1038/s41467-021-24432-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Accepted: 06/08/2021] [Indexed: 02/06/2023] Open
Abstract
The folding of β-barrel outer membrane proteins (OMPs) in Gram-negative bacteria is catalysed by the β-barrel assembly machinery (BAM). How lateral opening in the β-barrel of the major subunit BamA assists in OMP folding, and the contribution of membrane disruption to BAM catalysis remain unresolved. Here, we use an anti-BamA monoclonal antibody fragment (Fab1) and two disulphide-crosslinked BAM variants (lid-locked (LL), and POTRA-5-locked (P5L)) to dissect these roles. Despite being lethal in vivo, we show that all complexes catalyse folding in vitro, albeit less efficiently than wild-type BAM. CryoEM reveals that while Fab1 and BAM-P5L trap an open-barrel state, BAM-LL contains a mixture of closed and contorted, partially-open structures. Finally, all three complexes globally destabilise the lipid bilayer, while BamA does not, revealing that the BAM lipoproteins are required for this function. Together the results provide insights into the role of BAM structure and lipid dynamics in OMP folding.
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30
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Wu X, Rapoport TA. Translocation of Proteins through a Distorted Lipid Bilayer. Trends Cell Biol 2021; 31:473-484. [PMID: 33531207 PMCID: PMC8122044 DOI: 10.1016/j.tcb.2021.01.002] [Citation(s) in RCA: 43] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2020] [Revised: 01/05/2021] [Accepted: 01/07/2021] [Indexed: 12/13/2022]
Abstract
Membranes surrounding cells or organelles represent barriers to proteins and other molecules. However, specific proteins can cross membranes by different translocation systems, the best studied being the Sec61/SecY channel. This channel forms a hydrophilic, hourglass-shaped membrane channel, with a lateral gate towards the surrounding lipid. However, recent studies show that an aqueous pore is not required in other cases of protein translocation. The Hrd1 complex, mediating the retrotranslocation of misfolded proteins from the endoplasmic reticulum (ER) lumen into the cytosol, contains multispanning proteins with aqueous luminal and cytosolic cavities, and lateral gates juxtaposed in a thinned membrane region. A locally thinned, distorted lipid bilayer also allows protein translocation in other systems, suggesting a new paradigm to overcome the membrane barrier.
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Affiliation(s)
- Xudong Wu
- Howard Hughes Medical Institute and Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA
| | - Tom A Rapoport
- Howard Hughes Medical Institute and Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA.
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31
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Ranava D, Yang Y, Orenday-Tapia L, Rousset F, Turlan C, Morales V, Cui L, Moulin C, Froment C, Munoz G, Rech J, Marcoux J, Caumont-Sarcos A, Albenne C, Bikard D, Ieva R. Lipoprotein DolP supports proper folding of BamA in the bacterial outer membrane promoting fitness upon envelope stress. eLife 2021; 10:67817. [PMID: 33847565 PMCID: PMC8081527 DOI: 10.7554/elife.67817] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Accepted: 04/04/2021] [Indexed: 01/03/2023] Open
Abstract
In Proteobacteria, integral outer membrane proteins (OMPs) are crucial for the maintenance of the envelope permeability barrier to some antibiotics and detergents. In Enterobacteria, envelope stress caused by unfolded OMPs activates the sigmaE (σE) transcriptional response. σE upregulates OMP biogenesis factors, including the β-barrel assembly machinery (BAM) that catalyses OMP folding. Here we report that DolP (formerly YraP), a σE-upregulated and poorly understood outer membrane lipoprotein, is crucial for fitness in cells that undergo envelope stress. We demonstrate that DolP interacts with the BAM complex by associating with outer membrane-assembled BamA. We provide evidence that DolP is important for proper folding of BamA that overaccumulates in the outer membrane, thus supporting OMP biogenesis and envelope integrity. Notably, mid-cell recruitment of DolP had been linked to regulation of septal peptidoglycan remodelling by an unknown mechanism. We now reveal that, during envelope stress, DolP loses its association with the mid-cell, thereby suggesting a mechanistic link between envelope stress caused by impaired OMP biogenesis and the regulation of a late step of cell division.
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Affiliation(s)
- David Ranava
- Laboratoire de Microbiologie et Génétique Moléculaires (LMGM), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Yiying Yang
- Laboratoire de Microbiologie et Génétique Moléculaires (LMGM), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Luis Orenday-Tapia
- Laboratoire de Microbiologie et Génétique Moléculaires (LMGM), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, Toulouse, France
| | - François Rousset
- Synthetic Biology Group, Microbiology Department, Institut Pasteur, Paris, France
| | - Catherine Turlan
- Laboratoire de Microbiologie et Génétique Moléculaires (LMGM), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Violette Morales
- Laboratoire de Microbiologie et Génétique Moléculaires (LMGM), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Lun Cui
- Synthetic Biology Group, Microbiology Department, Institut Pasteur, Paris, France
| | - Cyril Moulin
- Laboratoire de Microbiologie et Génétique Moléculaires (LMGM), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Carine Froment
- Institut de Pharmacologie et de Biologie Structurale (IPBS), Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Gladys Munoz
- Laboratoire de Microbiologie et Génétique Moléculaires (LMGM), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Jérôme Rech
- Laboratoire de Microbiologie et Génétique Moléculaires (LMGM), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Julien Marcoux
- Institut de Pharmacologie et de Biologie Structurale (IPBS), Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Anne Caumont-Sarcos
- Laboratoire de Microbiologie et Génétique Moléculaires (LMGM), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Cécile Albenne
- Laboratoire de Microbiologie et Génétique Moléculaires (LMGM), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, Toulouse, France
| | - David Bikard
- Synthetic Biology Group, Microbiology Department, Institut Pasteur, Paris, France
| | - Raffaele Ieva
- Laboratoire de Microbiologie et Génétique Moléculaires (LMGM), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, Toulouse, France
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32
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Doyle MT, Bernstein HD. BamA forms a translocation channel for polypeptide export across the bacterial outer membrane. Mol Cell 2021; 81:2000-2012.e3. [PMID: 33705710 DOI: 10.1016/j.molcel.2021.02.023] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Revised: 01/05/2021] [Accepted: 02/18/2021] [Indexed: 12/18/2022]
Abstract
The β-barrel assembly machine (BAM) integrates β-barrel proteins into the outer membrane (OM) of Gram-negative bacteria. An essential BAM subunit (BamA) catalyzes integration by promoting the formation of a hybrid-barrel intermediate state between its own β-barrel domain and that of its client proteins. Here we show that in addition to catalyzing the integration of β-barrel proteins, BamA functions as a polypeptide export channel. In vivo structural mapping via intermolecular disulfide crosslinking showed that the extracellular "passenger" domain of a member of the "autotransporter" superfamily of virulence factors traverses the OM through the BamA β-barrel lumen. Furthermore, we demonstrate that a highly conserved residue within autotransporter β-barrels is required to position the passenger inside BamA to initiate translocation and that during translocation, the passenger stabilizes the hybrid-barrel state. Our results not only establish a new function for BamA but also unify the divergent functions of BamA and other "Omp85" superfamily transporters.
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Affiliation(s)
- Matthew Thomas Doyle
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Harris David Bernstein
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
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