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Pumirat P, Santajit S, Tunyong W, Kong-Ngoen T, Tandhavanant S, Lohitthai S, Rungruengkitkun A, Chantratita N, Ampawong S, Reamtong O, Indrawattana N. Impact of AbaI mutation on virulence, biofilm development, and antibiotic susceptibility in Acinetobacter baumannii. Sci Rep 2024; 14:21521. [PMID: 39277662 PMCID: PMC11401864 DOI: 10.1038/s41598-024-72740-1] [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: 05/17/2024] [Accepted: 09/10/2024] [Indexed: 09/17/2024] Open
Abstract
The quorum sensing (QS) system mediated by the abaI gene in Acinetobacter baumannii is crucial for various physiological and pathogenic processes. In this study, we constructed a stable markerless abaI knockout mutant (ΔabaI) strain using a pEXKm5-based allele replacement method to investigate the impact of abaI on A. baumannii. Proteomic analysis revealed significant alterations in protein expression between the wild type (WT) and ΔabaI mutant strains, particularly in proteins associated with membrane structure, antibiotic resistance, and virulence. Notably, the downregulation of key outer membrane proteins such as SurA, OmpA, OmpW, and BamA suggests potential vulnerabilities in outer membrane integrity, which correlate with structural abnormalities in the ΔabaI mutant strain, including irregular cell shapes and compromised membrane integrity, observed by scanning and transmission electron microscopy. Furthermore, diminished expression of regulatory proteins such as OmpR and GacA-GacS highlights the broader regulatory networks affected by abaI deletion. Functional assays revealed impaired biofilm formation and surface-associated motility in the mutant strain, indicative of altered colonization capabilities. Interestingly, the mutant showed a complex antibiotic susceptibility profile. While it demonstrated increased susceptibility to membrane-targeting antibiotics, its response to beta-lactams was more nuanced. Despite increased expression of metallo-beta-lactamase (MBL) superfamily proteins and DcaP-like protein, the mutant unexpectedly showed lower MICs for carbapenems (imipenem and meropenem) compared to the wild-type strain. This suggests that abaI deletion affects antibiotic susceptibility through multiple, potentially competing mechanisms. Further investigation is needed to fully elucidate the interplay between quorum sensing, antibiotic resistance genes, and overall antibiotic susceptibility in A. baumannii. Our findings underscore the multifaceted role of the abaI gene in modulating various cellular processes and highlight its significance in A. baumannii physiology, pathogenesis, and antibiotic resistance. Targeting the abaI QS system may offer novel therapeutic strategies for this clinically significant pathogen.
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Affiliation(s)
- Pornpan Pumirat
- Department of Microbiology and Immunology, Mahidol University, Bangkok, Thailand
| | - Sirijan Santajit
- Department of Medical Technology, School of Allied Health Sciences, Walailak University, Nakhon Si Thammarat, Thailand
| | - Witawat Tunyong
- Department of Microbiology and Immunology, Mahidol University, Bangkok, Thailand
| | - Thida Kong-Ngoen
- Department of Microbiology and Immunology, Mahidol University, Bangkok, Thailand
| | - Sarunporn Tandhavanant
- Department of Microbiology and Immunology, Mahidol University, Bangkok, Thailand
- Department of Bacteriology, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan
| | - Sanisa Lohitthai
- Department of Microbiology and Immunology, Mahidol University, Bangkok, Thailand
| | | | - Narisara Chantratita
- Department of Microbiology and Immunology, Mahidol University, Bangkok, Thailand
| | - Sumate Ampawong
- Department of Tropical Pathology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Onrapak Reamtong
- Department of Tropical Molecular Biology and Genetics, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Nitaya Indrawattana
- Biomedical Research Incubator Unit, Department of Research, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand.
- Department of Research, Siriraj Center of Research Excellence in Allergy and Immunology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand.
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2
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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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3
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Yoshimoto S, Aoki S, Ohara Y, Ishikawa M, Suzuki A, Linke D, Lupas AN, Hori K. Identification of the adhesive domain of AtaA from Acinetobacter sp. Tol 5 and its application in immobilizing Escherichia coli. Front Bioeng Biotechnol 2023; 10:1095057. [PMID: 36698637 PMCID: PMC9868564 DOI: 10.3389/fbioe.2022.1095057] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Accepted: 12/21/2022] [Indexed: 01/11/2023] Open
Abstract
Cell immobilization is an important technique for efficiently utilizing whole-cell biocatalysts. We previously invented a method for bacterial cell immobilization using AtaA, a trimeric autotransporter adhesin from the highly sticky bacterium Acinetobacter sp. Tol 5. However, except for Acinetobacter species, only one bacterium has been successfully immobilized using AtaA. This is probably because the heterologous expression of large AtaA (1 MDa), that is a homotrimer of polypeptide chains composed of 3,630 amino acids, is difficult. In this study, we identified the adhesive domain of AtaA and constructed a miniaturized AtaA (mini-AtaA) to improve the heterologous expression of ataA. In-frame deletion mutants were used to perform functional mapping, revealing that the N-terminal head domain is essential for the adhesive feature of AtaA. The mini-AtaA, which contains a homotrimer of polypeptide chains from 775 amino acids and lacks the unnecessary part for its adhesion, was properly expressed in E. coli, and a larger amount of molecules was displayed on the cell surface than that of full-length AtaA (FL-AtaA). The immobilization ratio of E. coli cells expressing mini-AtaA on a polyurethane foam support was significantly higher compared to the cells with or without FL-AtaA expression, respectively. The expression of mini-AtaA in E. coli had little effect on the cell growth and the activity of another enzyme reflecting the production level, and the immobilized E. coli cells could be used for repetitive enzymatic reactions as a whole-cell catalyst.
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Affiliation(s)
- Shogo Yoshimoto
- Department of Biomolecular Engineering, Graduate School of Engineering, Nagoya University, Nagoya, Japan
| | - Sota Aoki
- Department of Biomolecular Engineering, Graduate School of Engineering, Nagoya University, Nagoya, Japan
| | - Yuki Ohara
- Department of Biomolecular Engineering, Graduate School of Engineering, Nagoya University, Nagoya, Japan
| | - Masahito Ishikawa
- Department of Biomolecular Engineering, Graduate School of Engineering, Nagoya University, Nagoya, Japan
| | - Atsuo Suzuki
- Department of Biomolecular Engineering, Graduate School of Engineering, Nagoya University, Nagoya, Japan
| | - Dirk Linke
- Department of Biosciences, University of Oslo, Oslo, Norway
| | - Andrei N. Lupas
- Department of Protein Evolution, Max Planck Institute for Biology, Tübingen, Germany
| | - Katsutoshi Hori
- Department of Biomolecular Engineering, Graduate School of Engineering, Nagoya University, Nagoya, Japan,*Correspondence: Katsutoshi Hori,
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4
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Abstract
Biocontainment is a safeguard strategy for preventing uncontrolled proliferation of genetically engineered microorganisms (GEMs) in the environment. Biocontained GEMs are designed to survive only in the presence of a specific molecule. The design of a pollutant-degrading and pollutant-dependent GEM prevents its proliferation after cleaning the environment. In this study, we present a biocontained toluene-degrading bacterium based on Acinetobacter sp. Tol 5. The bamA gene, which encodes an essential outer membrane protein, was deleted from the chromosome of Tol 5 but complemented with a plasmid carrying a bamA gene regulated by the Pu promoter and the regulatory protein XylR. The resultant strain (PuBamA) degraded toluene, similarly to the wild-type Tol 5. Although the cell growth of the PuBamA strain was remarkably inhibited after toluene depletion, escape mutants emerged at a frequency of 1 per 5.3 × 10−7 cells. Analyses of escape mutants revealed that insertion sequences (ISs) carrying promoters were inserted between the Pu promoter and the bamA gene on the complemented plasmid. MinION deep sequencing of the plasmids extracted from the escape mutants enabled the identification of three types of ISs involved in the emergence of escape mutants, suggesting a strategy for reducing it. IMPORTANCE GEMs are beneficial for various applications, including environmental protection. However, the risks of GEM release into the environment have been debated for a long time. If a pollutant is employed as a specific molecule for a biocontainment system, GEMs capable of degrading pollutants are available for environmental protection. Nevertheless, to our knowledge, biocontained degraders for real pollutants have not been reported in academic journals so far. This is possibly due to the difficulty in the expression of enzymes for degrading pollutants in a tractable bacterium such as Escherichia coli. On the other hand, bacteria with enzymes for degrading pollutants are often intractable as a host of GEMs due to the shortage of tools for genetic manipulation. This study reports the feasibility of a biocontainment strategy for a toluene degrader. Our results provide useful insights into the construction of a GEM biocontainment system for environmental protection.
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Wu R, Stephenson R, Gichaba A, Noinaj N. The big BAM theory: An open and closed case? BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2019; 1862:183062. [PMID: 31520605 DOI: 10.1016/j.bbamem.2019.183062] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2019] [Revised: 09/02/2019] [Accepted: 09/04/2019] [Indexed: 12/16/2022]
Abstract
The β-barrel assembly machinery (BAM) is responsible for the biogenesis of outer membrane proteins (OMPs) into the outer membranes of Gram-negative bacteria. These OMPs have a membrane-embedded domain consisting of a β-barrel fold which can vary from 8 to 36 β-strands, with each serving a diverse role in the cell such as nutrient uptake and virulence. BAM was first identified nearly two decades ago, but only recently has the molecular structure of the full complex been reported. Together with many years of functional characterization, we have a significantly clearer depiction of BAM's structure, the intra-complex interactions, conformational changes that BAM may undergo during OMP biogenesis, and the role chaperones may play. But still, despite advances over the past two decades, the mechanism for BAM-mediated OMP biogenesis remains elusive. Over the years, several theories have been proposed that have varying degrees of support from the literature, but none has of yet been conclusive enough to be widely accepted as the sole mechanism. We will present a brief history of BAM, the recent work on the structures of BAM, and a critical analysis of the current theories for how it may function.
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Affiliation(s)
- Runrun Wu
- Markey Center for Structural Biology, Department of Biological Sciences, and the Purdue Institute of Inflammation, Immunology and Infectious Disease, Purdue University, West Lafayette, IN, 47907, USA
| | - Robert Stephenson
- Markey Center for Structural Biology, Department of Biological Sciences, and the Purdue Institute of Inflammation, Immunology and Infectious Disease, Purdue University, West Lafayette, IN, 47907, USA
| | - Abigail Gichaba
- Markey Center for Structural Biology, Department of Biological Sciences, and the Purdue Institute of Inflammation, Immunology and Infectious Disease, Purdue University, West Lafayette, IN, 47907, USA
| | - Nicholas Noinaj
- Markey Center for Structural Biology, Department of Biological Sciences, and the Purdue Institute of Inflammation, Immunology and Infectious Disease, Purdue University, West Lafayette, IN, 47907, USA.
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6
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Leo JC, Linke D. A unified model for BAM function that takes into account type Vc secretion and species differences in BAM composition. AIMS Microbiol 2018; 4:455-468. [PMID: 31294227 PMCID: PMC6604945 DOI: 10.3934/microbiol.2018.3.455] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Accepted: 06/13/2018] [Indexed: 01/14/2023] Open
Abstract
Transmembrane proteins in the outer membrane of Gram-negative bacteria are almost exclusively β-barrels. They are inserted into the outer membrane by a conserved and essential protein complex called the BAM (for β-barrel assembly machinery). In this commentary, we summarize current research into the mechanism of this protein complex and how it relates to type V secretion. Type V secretion systems are autotransporters that all contain a β-barrel transmembrane domain inserted by BAM. In type Vc systems, this domain is a homotrimer. We argue that none of the current models are sufficient to explain BAM function particularly regarding type Vc secretion. We also find that current models based on the well-studied model system Escherichia coli mostly ignore the pronounced differences in BAM composition between different bacterial species. We propose a more holistic view on how all OMPs, including autotransporters, are incorporated into the lipid bilayer.
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Affiliation(s)
- Jack C Leo
- Department of Biosciences, University of Oslo, Blindernveien 31, 0316 Oslo, Norway
| | - Dirk Linke
- Department of Biosciences, University of Oslo, Blindernveien 31, 0316 Oslo, Norway
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7
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Pfitzner AK, Steblau N, Ulrich T, Oberhettinger P, Autenrieth IB, Schütz M, Rapaport D. Mitochondrial-bacterial hybrids of BamA/Tob55 suggest variable requirements for the membrane integration of β-barrel proteins. Sci Rep 2016; 6:39053. [PMID: 27982054 PMCID: PMC5159795 DOI: 10.1038/srep39053] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Accepted: 11/16/2016] [Indexed: 11/10/2022] Open
Abstract
β-Barrel proteins are found in the outer membrane (OM) of Gram-negative bacteria, chloroplasts and mitochondria. The assembly of these proteins into the corresponding OM is facilitated by a dedicated protein complex that contains a central conserved β-barrel protein termed BamA in bacteria and Tob55/Sam50 in mitochondria. BamA and Tob55 consist of a membrane-integral C-terminal domain that forms a β-barrel pore and a soluble N-terminal portion comprised of one (in Tob55) or five (in BamA) polypeptide transport-associated (POTRA) domains. Currently the functional significance of this difference and whether the homology between BamA and Tob55 can allow them to replace each other are unclear. To address these issues we constructed hybrid Tob55/BamA proteins with differently configured N-terminal POTRA domains. We observed that constructs harboring a heterologous C-terminal domain could not functionally replace the bacterial BamA or the mitochondrial Tob55 demonstrating species-specific requirements. Interestingly, the various hybrid proteins in combination with the bacterial chaperones Skp or SurA supported to a variable extent the assembly of bacterial β-barrel proteins into the mitochondrial OM. Collectively, our findings suggest that the membrane assembly of various β-barrel proteins depends to a different extent on POTRA domains and periplasmic chaperones.
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Affiliation(s)
| | - Nadja Steblau
- Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, 72076 Tübingen, Germany
| | - Thomas Ulrich
- Interfaculty Institute of Biochemistry, University of Tübingen, 72076 Tübingen, Germany
| | - Philipp Oberhettinger
- Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, 72076 Tübingen, Germany
| | - Ingo B Autenrieth
- Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, 72076 Tübingen, Germany
| | - Monika Schütz
- Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, 72076 Tübingen, Germany
| | - Doron Rapaport
- Interfaculty Institute of Biochemistry, University of Tübingen, 72076 Tübingen, Germany
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8
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Zielke RA, Wierzbicki IH, Baarda BI, Gafken PR, Soge OO, Holmes KK, Jerse AE, Unemo M, Sikora AE. Proteomics-driven Antigen Discovery for Development of Vaccines Against Gonorrhea. Mol Cell Proteomics 2016; 15:2338-55. [PMID: 27141096 PMCID: PMC4937508 DOI: 10.1074/mcp.m116.058800] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2016] [Revised: 04/25/2016] [Indexed: 12/18/2022] Open
Abstract
Expanding efforts to develop preventive gonorrhea vaccines is critical because of the dire possibility of untreatable gonococcal infections. Reverse vaccinology, which includes genome and proteome mining, has proven very successful in the discovery of vaccine candidates against many pathogenic bacteria. However, progress with this approach for a gonorrhea vaccine remains in its infancy. Accordingly, we applied a comprehensive proteomic platform-isobaric tagging for absolute quantification coupled with two-dimensional liquid chromatography and mass spectrometry-to identify potential gonococcal vaccine antigens. Our previous analyses focused on cell envelopes and naturally released membrane vesicles derived from four different Neisseria gonorrhoeae strains. Here, we extended these studies to identify cell envelope proteins of N. gonorrhoeae that are ubiquitously expressed and specifically induced by physiologically relevant environmental stimuli: oxygen availability, iron deprivation, and the presence of human serum. Together, these studies enabled the identification of numerous potential gonorrhea vaccine targets. Initial characterization of five novel vaccine candidate antigens that were ubiquitously expressed under these different growth conditions demonstrated that homologs of BamA (NGO1801), LptD (NGO1715), and TamA (NGO1956), and two uncharacterized proteins, NGO2054 and NGO2139, were surface exposed, secreted via naturally released membrane vesicles, and elicited bactericidal antibodies that cross-reacted with a panel of temporally and geographically diverse isolates. In addition, analysis of polymorphisms at the nucleotide and amino acid levels showed that these vaccine candidates are highly conserved among N. gonorrhoeae strains. Finally, depletion of BamA caused a loss of N. gonorrhoeae viability, suggesting it may be an essential target. Together, our data strongly support the use of proteomics-driven discovery of potential vaccine targets as a sound approach for identifying promising gonococcal antigens.
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Affiliation(s)
- Ryszard A Zielke
- From the ‡Department of Pharmaceutical Sciences, College of Pharmacy, Oregon State University, Corvallis, Oregon
| | - Igor H Wierzbicki
- From the ‡Department of Pharmaceutical Sciences, College of Pharmacy, Oregon State University, Corvallis, Oregon
| | - Benjamin I Baarda
- From the ‡Department of Pharmaceutical Sciences, College of Pharmacy, Oregon State University, Corvallis, Oregon
| | - Philip R Gafken
- §Proteomics Facility, Fred Hutchinson Cancer Research Center, Seattle, Washington
| | - Olusegun O Soge
- ¶Neisseria Reference Laboratory, Department of Global Health, University of Washington, Seattle, Washington
| | - King K Holmes
- ¶Neisseria Reference Laboratory, Department of Global Health, University of Washington, Seattle, Washington; ‖Departments of Medicine and Global Health, University of Washington, Seattle, Washington
| | - Ann E Jerse
- **Department of Microbiology and Immunology, F. Edward Herbert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland
| | - Magnus Unemo
- ‡‡WHO Collaborating Centre for Gonorrhoea and other Sexually Transmitted Infections, National Reference Laboratory for Pathogenic Neisseria, Department of Laboratory Medicine, Microbiology, Örebro University Hospital, Örebro, Sweden
| | - Aleksandra E Sikora
- From the ‡Department of Pharmaceutical Sciences, College of Pharmacy, Oregon State University, Corvallis, Oregon;
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Browning DF, Bavro VN, Mason JL, Sevastsyanovich YR, Rossiter AE, Jeeves M, Wells TJ, Knowles TJ, Cunningham AF, Donald JW, Palmer T, Overduin M, Henderson IR. Cross-species chimeras reveal BamA POTRA and β-barrel domains must be fine-tuned for efficient OMP insertion. Mol Microbiol 2015; 97:646-59. [PMID: 25943387 PMCID: PMC4950039 DOI: 10.1111/mmi.13052] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
BAM is a conserved molecular machine, the central component of which is BamA. Orthologues of BamA are found in all Gram-negative bacteria, chloroplasts and mitochondria where it is required for the folding and insertion of β-barrel containing integral outer membrane proteins (OMPs) into the outer membrane. BamA binds unfolded β-barrel precursors via the five polypeptide transport-associated (POTRA) domains at its N-terminus. The C-terminus of BamA folds into a β-barrel domain, which tethers BamA to the outer membrane and is involved in OMP insertion. BamA orthologues are found in all Gram-negative bacteria and appear to function in a species-specific manner. Here we investigate the nature of this species-specificity by examining whether chimeric Escherichia coli BamA fusion proteins, carrying either the β-barrel or POTRA domains from various BamA orthologues, can functionally replace E. coli BamA. We demonstrate that the β-barrel domains of many BamA orthologues are functionally interchangeable. We show that defects in the orthologous POTRA domains can be rescued by compensatory mutations within the β-barrel. These data reveal that the POTRA and barrel domains must be precisely aligned to ensure efficient OMP insertion.
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Affiliation(s)
- Douglas F Browning
- Institute of Microbiology and Infection, University of Birmingham, Birmingham, B15 2TT, UK
| | - Vassiliy N Bavro
- Institute of Microbiology and Infection, University of Birmingham, Birmingham, B15 2TT, UK
| | - Jessica L Mason
- Institute of Microbiology and Infection, University of Birmingham, Birmingham, B15 2TT, UK
| | | | - Amanda E Rossiter
- Institute of Microbiology and Infection, University of Birmingham, Birmingham, B15 2TT, UK
| | - Mark Jeeves
- School of Cancer Sciences, University of Birmingham, Birmingham, B15 2TT, UK
| | - Timothy J Wells
- Institute of Microbiology and Infection, University of Birmingham, Birmingham, B15 2TT, UK
| | - Timothy J Knowles
- School of Cancer Sciences, University of Birmingham, Birmingham, B15 2TT, UK
| | - Adam F Cunningham
- Institute of Microbiology and Infection, University of Birmingham, Birmingham, B15 2TT, UK
| | - James W Donald
- College of Life Sciences, University of Dundee, Dundee, DD1 5EH, UK
| | - Tracy Palmer
- College of Life Sciences, University of Dundee, Dundee, DD1 5EH, UK
| | - Michael Overduin
- School of Cancer Sciences, University of Birmingham, Birmingham, B15 2TT, UK
| | - Ian R Henderson
- Institute of Microbiology and Infection, University of Birmingham, Birmingham, B15 2TT, UK
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10
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Vimala A, Ramakrishnan C, Gromiha MM. Identifying a potential receptor for the antibacterial peptide of sponge Axinella donnani endosymbiont. Gene 2015; 566:166-74. [PMID: 25939848 DOI: 10.1016/j.gene.2015.04.070] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2015] [Revised: 04/03/2015] [Accepted: 04/15/2015] [Indexed: 11/30/2022]
Abstract
Marine sponges and their associated bacteria are rich sources of novel secondary metabolites with therapeutic usefulness. In our earlier work, we have identified a novel antibacterial peptide from the marine sponge Axinella donnani endosymbiotic bacteria. In this work, we have carried out a comparative genomic analysis and identified a set of 60 proteins as probable receptor which is common in all the strains. The analysis on binding substrate showed that β barrel assembly machinery (BamA) of the outer membrane protein 85 (omp85) superfamily is a potential receptor protein for the antibacterial peptide. It plays a central role in OMP biogenesis, especially in cell viability. Further, the triplet and quartet motifs RGF and YGDG, respectively in L6 loop are conserved over all the strains and these conserved residues interact with antibacterial peptide to inhibit the BamA function, which is essential for OMP biogenesis.
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Affiliation(s)
- A Vimala
- Department of Biotechnology, Indian Institute of Technology Madras, Chennai 600036 Tamilnadu, India.
| | - C Ramakrishnan
- Department of Biotechnology, Indian Institute of Technology Madras, Chennai 600036 Tamilnadu, India
| | - M Michael Gromiha
- Department of Biotechnology, Indian Institute of Technology Madras, Chennai 600036 Tamilnadu, India.
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11
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Dunn JP, Kenedy MR, Iqbal H, Akins DR. Characterization of the β-barrel assembly machine accessory lipoproteins from Borrelia burgdorferi. BMC Microbiol 2015; 15:70. [PMID: 25887384 PMCID: PMC4377024 DOI: 10.1186/s12866-015-0411-y] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2015] [Accepted: 03/12/2015] [Indexed: 12/26/2022] Open
Abstract
Background Like all diderm bacteria studied to date, Borrelia burgdorferi possesses a β-barrel assembly machine (BAM) complex. The bacterial BAM complexes characterized thus far consist of an essential integral outer membrane protein designated BamA and one or more accessory proteins. The accessory proteins are typically lipid-modified proteins anchored to the inner leaflet of the outer membrane through their lipid moieties. We previously identified and characterized the B. burgdorferi BamA protein in detail and more recently identified two lipoproteins encoded by open reading frames bb0324 and bb0028 that associate with the borrelial BamA protein. The role(s) of the BAM accessory lipoproteins in B. burgdorferi is currently unknown. Results Structural modeling of B. burgdorferi BB0028 revealed a distinct β-propeller fold similar to the known structure for the E. coli BAM accessory lipoprotein BamB. Additionally, the structural model for BB0324 was highly similar to the known structure of BamD, which is consistent with the prior finding that BB0324 contains tetratricopeptide repeat regions similar to other BamD orthologs. Consistent with BB0028 and BB0324 being BAM accessory lipoproteins, mutants lacking expression of each protein were found to exhibit altered membrane permeability and enhanced sensitivity to various antimicrobials. Additionally, BB0028 mutants also exhibited significantly impaired in vitro growth. Finally, immunoprecipitation experiments revealed that BB0028 and BB0324 each interact specifically and independently with BamA to form the BAM complex in B. burgdorferi. Conclusions Combined structural studies, functional assays, and co-immunoprecipitation experiments confirmed that BB0028 and BB0324 are the respective BamB and BamD orthologs in B. burgdorferi, and are important in membrane integrity and/or outer membrane protein localization. The borrelial BamB and BamD proteins both interact specifically and independently with BamA to form a tripartite BAM complex in B. burgdorferi. A working model has been developed to further analyze outer membrane biogenesis and outer membrane protein transport in this pathogenic spirochete.
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Affiliation(s)
- Joshua P Dunn
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73104, USA.
| | - Melisha R Kenedy
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73104, USA.
| | - Henna Iqbal
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73104, USA.
| | - Darrin R Akins
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73104, USA.
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12
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Abstract
The outer membranes of gram-negative bacteria contain integral membrane proteins, most of which are of β-barrel structure, and critical for bacterial survival. These β-barrel proteins rely on the β-barrel assembly machinery (BAM) complex for their integration into the outer membrane as folded species. The central and essential subunit of the BAM complex, BamA, is a β-barrel protein conserved in all gram-negative bacteria and also found in eukaryotic organelles derived from bacterial endosymbionts. In Escherichia coli, BamA docks with four peripheral lipoproteins, BamB, BamC, BamD and BamE, partner subunits that add to the function of the BAM complex in outer membrane protein biogenesis. By way of introduction to this volume, we provide an overview of the work that has illuminated the mechanism by which the BAM complex drives β-barrel assembly. The protocols and methodologies associated with these studies as well as the challenges encountered and their elegant solutions are discussed in subsequent chapters.
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Albrecht R, Schütz M, Oberhettinger P, Faulstich M, Bermejo I, Rudel T, Diederichs K, Zeth K. Structure of BamA, an essential factor in outer membrane protein biogenesis. ACTA ACUST UNITED AC 2014; 70:1779-89. [PMID: 24914988 DOI: 10.1107/s1399004714007482] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2013] [Accepted: 04/03/2014] [Indexed: 11/10/2022]
Abstract
Outer membrane protein (OMP) biogenesis is an essential process for maintaining the bacterial cell envelope and involves the β-barrel assembly machinery (BAM) for OMP recognition, folding and assembly. In Escherichia coli this function is orchestrated by five proteins: the integral outer membrane protein BamA of the Omp85 superfamily and four associated lipoproteins. To unravel the mechanism underlying OMP folding and insertion, the structure of the E. coli BamA β-barrel and P5 domain was determined at 3 Å resolution. These data add information beyond that provided in the recently published crystal structures of BamA from Haemophilus ducreyi and Neisseria gonorrhoeae and are a valuable basis for the interpretation of pertinent functional studies. In an `open' conformation, E. coli BamA displays a significant degree of flexibility between P5 and the barrel domain, which is indicative of a multi-state function in substrate transfer. E. coli BamA is characterized by a discontinuous β-barrel with impaired β1-β16 strand interactions denoted by only two connecting hydrogen bonds and a disordered C-terminus. The 16-stranded barrel surrounds a large cavity which implies a function in OMP substrate binding and partial folding. These findings strongly support a mechanism of OMP biogenesis in which substrates are partially folded inside the barrel cavity and are subsequently released laterally into the lipid bilayer.
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Affiliation(s)
- Reinhard Albrecht
- Department of Protein Evolution, Max-Planck-Institut für Entwicklungsbiologie, Spemannstrasse 35, 72076 Tübingen, Germany
| | - Monika Schütz
- Institut für Medizinische Mikrobiologie und Hygiene, Elfriede-Aulhorn-Strasse 6, 72076 Tübingen, Germany
| | - Philipp Oberhettinger
- Institut für Medizinische Mikrobiologie und Hygiene, Elfriede-Aulhorn-Strasse 6, 72076 Tübingen, Germany
| | - Michaela Faulstich
- Department for Microbiology, Biocenter of the University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Ivan Bermejo
- Unidad de Biofisica (CSIC-UPV/EHU), Barrio Sarriena s/n, 48940 Leioa, Vizcaya, Spain
| | - Thomas Rudel
- Department for Microbiology, Biocenter of the University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Kay Diederichs
- Department of Biology, University of Konstanz, 78457 Konstanz, Germany
| | - Kornelius Zeth
- Department of Protein Evolution, Max-Planck-Institut für Entwicklungsbiologie, Spemannstrasse 35, 72076 Tübingen, Germany
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