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Nash ZM, Inatsuka CS, Cotter PA, Johnson RM. Bordetella filamentous hemagglutinin and adenylate cyclase toxin interactions on the bacterial surface are consistent with FhaB-mediated delivery of ACT to phagocytic cells. mBio 2024; 15:e0063224. [PMID: 38534159 PMCID: PMC11077949 DOI: 10.1128/mbio.00632-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2024] [Accepted: 03/07/2024] [Indexed: 03/28/2024] Open
Abstract
Bordetella species that cause respiratory infections in mammals include B. pertussis, which causes human whooping cough, and B. bronchiseptica, which infects nearly all mammals. Both bacterial species produce filamentous hemagglutinin (FhaB) and adenylate cyclase toxin (ACT), prominent surface-associated and secreted virulence factors that contribute to persistence in the lower respiratory tract by inhibiting clearance by phagocytic cells. FhaB and ACT proteins interact with themselves, each other, and host cells. Using immunoblot analyses, we showed that ACT binds to FhaB on the bacterial surface before it can be detected in culture supernatants. We determined that SphB1, a surface protease identified based on its requirement for FhaB cleavage, is also required for ACT cleavage, and we determined that the presence of ACT blocks SphB1-dependent and -independent cleavage of FhaB, but the presence of FhaB does not affect SphB1-dependent cleavage of ACT. The primary SphB1-dependent cleavage site on ACT is proximal to ACT's active site, in a region that is critical for ACT activity. We also determined that FhaB-bound ACT on the bacterial surface can intoxicate host cells producing CR3, the receptor for ACT. In addition to increasing our understanding of FhaB, ACT, and FhaB-ACT interactions on the Bordetella surface, our data are consistent with a model in which FhaB functions as a novel toxin delivery system by binding to ACT and allowing its release upon binding of ACT to its receptor, CR3, on phagocytic cells.IMPORTANCEBacteria need to control the variety, abundance, and conformation of proteins on their surface to survive. Members of the Gram-negative bacterial genus Bordetella include B. pertussis, which causes whooping cough in humans, and B. bronchiseptica, which causes respiratory infections in a broad range of mammals. These species produce two prominent virulence factors, the two-partner secretion (TPS) effector FhaB and adenylate cyclase toxin (ACT), that interact with themselves, each other, and host cells. Here, we determined that ACT binds FhaB on the bacterial surface before being detected in culture supernatants and that ACT bound to FhaB can be delivered to eukaryotic cells. Our data are consistent with a model in which FhaB delivers ACT specifically to phagocytic cells. This is the first report of a TPS system facilitating the delivery of a separate polypeptide toxin to target cells and expands our understanding of how TPS systems contribute to bacterial pathogenesis.
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Affiliation(s)
- Zachary M. Nash
- Department of Microbiology and Immunology, School of Medicine, University of North Carolina-Chapel Hill, Chapel Hill, North Carolina, USA
| | - Carol S. Inatsuka
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, California, USA
| | - Peggy A. Cotter
- Department of Microbiology and Immunology, School of Medicine, University of North Carolina-Chapel Hill, Chapel Hill, North Carolina, USA
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, California, USA
| | - Richard M. Johnson
- Department of Microbiology and Immunology, School of Medicine, University of North Carolina-Chapel Hill, Chapel Hill, North Carolina, USA
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Ntui CM, Fleckenstein JM, Schubert WD. Structural and biophysical characterization of the secreted, β-helical adhesin EtpA of Enterotoxigenic Escherichia coli. PLoS One 2023; 18:e0287100. [PMID: 37343026 PMCID: PMC10284417 DOI: 10.1371/journal.pone.0287100] [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: 03/07/2023] [Accepted: 05/30/2023] [Indexed: 06/23/2023] Open
Abstract
Enterotoxigenic Escherichia coli (ETEC) is a diarrhoeal pathogen associated with high morbidity and mortality especially among young children in developing countries. At present, there is no vaccine for ETEC. One candidate vaccine antigen, EtpA, is a conserved secreted adhesin that binds to the tips of flagellae to bridge ETEC to host intestinal glycans. EtpA is exported through a Gram-negative, two-partner secretion system (TPSS, type Vb) comprised of the secreted EtpA passenger (TpsA) protein and EtpB (TpsB) transporter that is integrated into the outer bacterial membrane. TpsA proteins share a conserved, N-terminal TPS domain followed by an extensive C-terminal domain with divergent sequence repeats. Two soluble, N-terminal constructs of EtpA were prepared and analysed respectively including residues 67 to 447 (EtpA67-447) and 1 to 606 (EtpA1-606). The crystal structure of EtpA67-447 solved at 1.76 Å resolution revealed a right-handed parallel β-helix with two extra-helical hairpins and an N-terminal β-strand cap. Analyses by circular dichroism spectroscopy confirmed the β-helical fold and indicated high resistance to chemical and thermal denaturation as well as rapid refolding. A theoretical AlphaFold model of full-length EtpA largely concurs with the crystal structure adding an extended β-helical C-terminal domain after an interdomain kink. We propose that robust folding of the TPS domain upon secretion provides a template to extend the N-terminal β-helix into the C-terminal domains of TpsA proteins.
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Affiliation(s)
- Clifford Manyo Ntui
- Department of Biochemistry, Genetics and Microbiology, University of Pretoria, Pretoria, South Africa
| | - James M. Fleckenstein
- Department of Medicine, Division of Infectious Diseases Washington University in Saint Louis, School of Medicine, Saint Louis, Missouri, United States of Ameirca
- Infectious Disease Service Saint Louis VA Health Care System, Saint Louis, Missouri, United States of Ameirca
| | - Wolf-Dieter Schubert
- Department of Biochemistry, Genetics and Microbiology, University of Pretoria, Pretoria, South Africa
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Niemiec MJ, Kapitan M, Himmel M, Döll K, Krüger T, Köllner TG, Auge I, Kage F, Alteri CJ, Mobley HL, Monsen T, Linde S, Nietzsche S, Kniemeyer O, Brakhage AA, Jacobsen ID. Augmented Enterocyte Damage During Candida albicans and Proteus mirabilis Coinfection. Front Cell Infect Microbiol 2022; 12:866416. [PMID: 35651758 PMCID: PMC9149288 DOI: 10.3389/fcimb.2022.866416] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Accepted: 04/15/2022] [Indexed: 12/24/2022] Open
Abstract
The human gut acts as the main reservoir of microbes and a relevant source of life-threatening infections, especially in immunocompromised patients. There, the opportunistic fungal pathogen Candida albicans adapts to the host environment and additionally interacts with residing bacteria. We investigated fungal-bacterial interactions by coinfecting enterocytes with the yeast Candida albicans and the Gram-negative bacterium Proteus mirabilis resulting in enhanced host cell damage. This synergistic effect was conserved across different P. mirabilis isolates and occurred also with non-albicans Candida species and C. albicans mutants defective in filamentation or candidalysin production. Using bacterial deletion mutants, we identified the P. mirabilis hemolysin HpmA to be the key effector for host cell destruction. Spatially separated coinfections demonstrated that synergism between Candida and Proteus is induced by contact, but also by soluble factors. Specifically, we identified Candida-mediated glucose consumption and farnesol production as potential triggers for Proteus virulence. In summary, our study demonstrates that coinfection of enterocytes with C. albicans and P. mirabilis can result in increased host cell damage which is mediated by bacterial virulence factors as a result of fungal niche modification via nutrient consumption and production of soluble factors. This supports the notion that certain fungal-bacterial combinations have the potential to result in enhanced virulence in niches such as the gut and might therefore promote translocation and dissemination.
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Affiliation(s)
- Maria Joanna Niemiec
- Leibniz Institute for Natural Product Research and Infection Biology – Hans Knöll Institute, Jena, Germany
- Center for Sepsis Control and Care, Jena, Germany
| | - Mario Kapitan
- Leibniz Institute for Natural Product Research and Infection Biology – Hans Knöll Institute, Jena, Germany
- Center for Sepsis Control and Care, Jena, Germany
| | - Maximilian Himmel
- Leibniz Institute for Natural Product Research and Infection Biology – Hans Knöll Institute, Jena, Germany
| | - Kristina Döll
- Leibniz Institute for Natural Product Research and Infection Biology – Hans Knöll Institute, Jena, Germany
| | - Thomas Krüger
- Leibniz Institute for Natural Product Research and Infection Biology – Hans Knöll Institute, Jena, Germany
| | - Tobias G. Köllner
- Department of Biochemistry, Max Planck Institute for Chemical Ecology, Jena, Germany
| | - Isabel Auge
- Leibniz Institute for Natural Product Research and Infection Biology – Hans Knöll Institute, Jena, Germany
| | - Franziska Kage
- Leibniz Institute for Natural Product Research and Infection Biology – Hans Knöll Institute, Jena, Germany
| | - Christopher J. Alteri
- Department of Natural Sciences, University of Michigan-Dearborn, Dearborn, MI, United States
| | - Harry L.T. Mobley
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI, United States
| | - Tor Monsen
- Department Clinical Microbiology, Umeå University, Umeå, Sweden
| | - Susanne Linde
- Center for Electron Microscopy, University Hospital, Jena, Germany
| | - Sandor Nietzsche
- Center for Electron Microscopy, University Hospital, Jena, Germany
| | - Olaf Kniemeyer
- Leibniz Institute for Natural Product Research and Infection Biology – Hans Knöll Institute, Jena, Germany
| | - Axel A. Brakhage
- Leibniz Institute for Natural Product Research and Infection Biology – Hans Knöll Institute, Jena, Germany
- Institute of Microbiology, Friedrich Schiller University, Jena, Germany
| | - Ilse D. Jacobsen
- Leibniz Institute for Natural Product Research and Infection Biology – Hans Knöll Institute, Jena, Germany
- Center for Sepsis Control and Care, Jena, Germany
- Institute of Microbiology, Friedrich Schiller University, Jena, Germany
- *Correspondence: Ilse D. Jacobsen,
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Abstract
Filamentous hemagglutinin (FhaB) is a critical virulence factor for both Bordetella pertussis, the causal agent of whooping cough, and the closely related species Bordetella bronchiseptica. FhaB is an adhesin, suppresses inflammatory cytokine production, and protects against phagocytic cell clearance during infection. Regulated degradation of the FhaB C-terminal prodomain is required to establish a persistent infection in mice. Two proteases, CtpA in the periplasm and SphB1 on the bacterial surface, are known to mediate FhaB processing, and we recently determined that CtpA functions before, and controls the FhaB cleavage site of, SphB1. However, the data indicate that another periplasmic protease must initiate degradation of the prodomain by removing a portion of the FhaB C terminus that inhibits CtpA-mediated degradation. Using a candidate approach, we identified DegP as the initiating protease. Deletion of degP or substitution of its predicted catalytic residue resulted in reduced creation of FHA′ (the main product of FhaB processing) and an accumulation of full-length FhaB in whole-cell lysates. Also, FHA′ was no longer released into culture supernatants in degP mutants. Alterations of the FhaB C terminus that relieve inhibition of CtpA abrogate the need for DegP, consistent with DegP functioning prior to CtpA in the processing pathway. DegP is not required for secretion of FhaB through FhaC or for adherence of the bacteria to host cells, indicating that DegP acts primarily as a protease and not a chaperone for FhaB in B. bronchiseptica. Our results highlight a role for HtrA family proteases in activation of virulence factors in pathogenic bacteria.
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Roussin M, Rabarioelina S, Cluzeau L, Cayron J, Lesterlin C, Salcedo SP, Bigot S. Identification of a Contact-Dependent Growth Inhibition (CDI) System That Reduces Biofilm Formation and Host Cell Adhesion of Acinetobacter baumannii DSM30011 Strain. Front Microbiol 2019; 10:2450. [PMID: 31736897 PMCID: PMC6831553 DOI: 10.3389/fmicb.2019.02450] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Accepted: 10/11/2019] [Indexed: 01/01/2023] Open
Abstract
Acinetobacter baumannii is a multidrug-resistant nosocomial opportunistic pathogen that is becoming a major health threat worldwide. In this study, we have focused on the A. baumannii DSM30011 strain, an environmental isolate that retains many virulence-associated traits. We found that its genome contains two loci encoding for contact-dependent growth inhibition (CDI) systems. These systems serve to kill or inhibit the growth of non-sibling bacteria by delivering toxins into the cytoplasm of target cells, thereby conferring the host strain a significant competitive advantage. We show that one of the two toxins functions as a DNA-damaging enzyme, capable of inducing DNA double-stranded breaks to the chromosome of Escherichia coli strain. The second toxin has unknown catalytic activity but stops the growth of E. coli without bactericidal effect. In our conditions, only one of the CDI systems was highly expressed in the A. baumannii DSM30011 strain and was found to mediate interbacterial competition. Surprisingly, the absence of this CDI system promotes adhesion of A. baumannii DSM30011 to both abiotic and biotic surfaces, a phenotype that differs from previously described CDI systems. Our results suggest that a specific regulation mediated by this A. baumannii DSM30011 CDI system may result in changes in bacterial physiology that repress host cell adhesion and biofilm formation.
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Affiliation(s)
- Morgane Roussin
- Cell Biology of Bacterial Pathogenicity Team, Laboratory of Molecular Microbiology and Structural Biochemistry, CNRS UMR 5086, University of Lyon, Lyon, France
| | - Sedera Rabarioelina
- Cell Biology of Bacterial Pathogenicity Team, Laboratory of Molecular Microbiology and Structural Biochemistry, CNRS UMR 5086, University of Lyon, Lyon, France
| | - Laurence Cluzeau
- Cell Biology of Bacterial Pathogenicity Team, Laboratory of Molecular Microbiology and Structural Biochemistry, CNRS UMR 5086, University of Lyon, Lyon, France
| | - Julien Cayron
- Cell to Cell DNA Transfer Team, Laboratory of Molecular Microbiology and Structural Biochemistry, CNRS UMR 5086, University of Lyon, Lyon, France
| | - Christian Lesterlin
- Cell to Cell DNA Transfer Team, Laboratory of Molecular Microbiology and Structural Biochemistry, CNRS UMR 5086, University of Lyon, Lyon, France
| | - Suzana P Salcedo
- Cell Biology of Bacterial Pathogenicity Team, Laboratory of Molecular Microbiology and Structural Biochemistry, CNRS UMR 5086, University of Lyon, Lyon, France
| | - Sarah Bigot
- Cell Biology of Bacterial Pathogenicity Team, Laboratory of Molecular Microbiology and Structural Biochemistry, CNRS UMR 5086, University of Lyon, Lyon, France.,Cell to Cell DNA Transfer Team, Laboratory of Molecular Microbiology and Structural Biochemistry, CNRS UMR 5086, University of Lyon, Lyon, France
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6
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Nash ZM, Cotter PA. Bordetella Filamentous Hemagglutinin, a Model for the Two-Partner Secretion Pathway. Microbiol Spectr 2019; 7:10.1128/microbiolspec.PSIB-0024-2018. [PMID: 30927348 PMCID: PMC6443250 DOI: 10.1128/microbiolspec.psib-0024-2018] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Indexed: 01/11/2023] Open
Abstract
Bacteria use a variety of mechanisms to translocate proteins from the cytoplasm, where they are synthesized, to the cell surface or extracellular environment or directly into other cells, where they perform their ultimate functions. Type V secretion systems (T5SS) use β-barrel transporter domains to export passenger domains across the outer membranes of Gram-negative bacteria. Distinct among T5SS are type Vb or two-partner secretion (TPS) systems in which the transporter and passenger are separate proteins, necessitating a mechanism for passenger-translocator recognition in the periplasm and providing the potential for reuse of the translocator. This review describes current knowledge of the TPS translocation mechanism, using Bordetella filamentous hemagglutinin (FHA) and its transporter FhaC as a model. We present the hypothesis that the TPS pathway may be a general mechanism for contact-dependent delivery of toxins to target cells.
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Affiliation(s)
- Zachary M. Nash
- Department of Microbiology and Immunology, University of North Carolina – Chapel Hill, Chapel Hill, NC, 27599-7290
| | - Peggy A. Cotter
- Department of Microbiology and Immunology, University of North Carolina – Chapel Hill, Chapel Hill, NC, 27599-7290
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7
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Guérin J, Bigot S, Schneider R, Buchanan SK, Jacob-Dubuisson F. Two-Partner Secretion: Combining Efficiency and Simplicity in the Secretion of Large Proteins for Bacteria-Host and Bacteria-Bacteria Interactions. Front Cell Infect Microbiol 2017; 7:148. [PMID: 28536673 PMCID: PMC5422565 DOI: 10.3389/fcimb.2017.00148] [Citation(s) in RCA: 66] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Accepted: 04/10/2017] [Indexed: 12/31/2022] Open
Abstract
Initially identified in pathogenic Gram-negative bacteria, the two-partner secretion (TPS) pathway, also known as Type Vb secretion, mediates the translocation across the outer membrane of large effector proteins involved in interactions between these pathogens and their hosts. More recently, distinct TPS systems have been shown to secrete toxic effector domains that participate in inter-bacterial competition or cooperation. The effects of these systems are based on kin vs. non-kin molecular recognition mediated by specific immunity proteins. With these new toxin-antitoxin systems, the range of TPS effector functions has thus been extended from cytolysis, adhesion, and iron acquisition, to genome maintenance, inter-bacterial killing and inter-bacterial signaling. Basically, a TPS system is made up of two proteins, the secreted TpsA effector protein and its TpsB partner transporter, with possible additional factors such as immunity proteins for protection against cognate toxic effectors. Structural studies have indicated that TpsA proteins mainly form elongated β helices that may be followed by specific functional domains. TpsB proteins belong to the Omp85 superfamily. Open questions remain on the mechanism of protein secretion in the absence of ATP or an electrochemical gradient across the outer membrane. The remarkable dynamics of the TpsB transporters and the progressive folding of their TpsA partners at the bacterial surface in the course of translocation are thought to be key elements driving the secretion process.
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Affiliation(s)
- Jeremy Guérin
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of HealthBethesda, MD, USA
| | - Sarah Bigot
- Molecular Microbiology and Structural Biochemistry, Centre National de La Recherche Scientifique UMR 5086-Université Lyon 1, Institute of Biology and Chemistry of ProteinsLyon, France
| | - Robert Schneider
- NMR and Molecular Interactions, Université de Lille, Centre National de La Recherche Scientifique, UMR 8576-Unité de Glycobiologie Structurale et FonctionnelleLille, France
| | - Susan K Buchanan
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of HealthBethesda, MD, USA
| | - Françoise Jacob-Dubuisson
- Université de Lille, Centre National de La Recherche Scientifique, Institut National de La Santé et de La Recherche Médicale, CHU Lille, Institut Pasteur de Lille, U1019-UMR 8204-Centre d'Infection et d'Immunité de LilleLille, France
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8
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Wimmer MR, Woods CN, Adamczak KJ, Glasgow EM, Novak WRP, Grilley DP, Weaver TM. Sequential unfolding of the hemolysin two-partner secretion domain from Proteus mirabilis. Protein Sci 2015; 24:1841-55. [PMID: 26350294 DOI: 10.1002/pro.2791] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2015] [Revised: 08/19/2015] [Accepted: 08/20/2015] [Indexed: 01/07/2023]
Abstract
Protein secretion is a major contributor to Gram-negative bacterial virulence. Type Vb or two-partner secretion (TPS) pathways utilize a membrane bound β-barrel B component (TpsB) to translocate large and predominantly virulent exoproteins (TpsA) through a nucleotide independent mechanism. We focused our studies on a truncated TpsA member termed hemolysin A (HpmA265), a structurally and functionally characterized TPS domain from Proteus mirabilis. Contrary to the expectation that the TPS domain of HpmA265 would denature in a single cooperative transition, we found that the unfolding follows a sequential model with three distinct transitions linking four states. The solvent inaccessible core of HpmA265 can be divided into two different regions. The C-proximal region contains nonpolar residues and forms a prototypical hydrophobic core as found in globular proteins. The N-proximal region of the solvent inaccessible core, however, contains polar residues. To understand the contributions of the hydrophobic and polar interiors to overall TPS domain stability, we conducted unfolding studies on HpmA265 and site-specific mutants of HpmA265. By correlating the effect of individual site-specific mutations with the sequential unfolding results we were able to divide the HpmA265 TPS domain into polar core, nonpolar core, and C-terminal subdomains. Moreover, the unfolding studies provide quantitative evidence that the folding free energy for the polar core subdomain is more favorable than for the nonpolar core and C-terminal subdomains. This study implicates the hydrogen bonds shared among these conserved internal residues as a primary means for stabilizing the N-proximal polar core subdomain.
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Affiliation(s)
- Megan R Wimmer
- Department of Chemistry and Biochemistry, University Wisconsin - La Crosse, La Crosse, Wisconsin, 54601
| | - Christopher N Woods
- Department of Chemistry and Biochemistry, University Wisconsin - La Crosse, La Crosse, Wisconsin, 54601
| | - Kyle J Adamczak
- Department of Chemistry and Biochemistry, University Wisconsin - La Crosse, La Crosse, Wisconsin, 54601
| | - Evan M Glasgow
- Department of Chemistry and Biochemistry, University Wisconsin - La Crosse, La Crosse, Wisconsin, 54601
| | - Walter R P Novak
- Department of Chemistry, Wabash College, Crawfordsville, Indiana, 47933
| | - Daniel P Grilley
- Department of Chemistry and Biochemistry, University Wisconsin - La Crosse, La Crosse, Wisconsin, 54601
| | - Todd M Weaver
- Department of Chemistry and Biochemistry, University Wisconsin - La Crosse, La Crosse, Wisconsin, 54601
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Structural determinants of the interaction between the TpsA and TpsB proteins in the Haemophilus influenzae HMW1 two-partner secretion system. J Bacteriol 2015; 197:1769-80. [PMID: 25777673 DOI: 10.1128/jb.00039-15] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2015] [Accepted: 02/26/2015] [Indexed: 12/20/2022] Open
Abstract
UNLABELLED The two-partner secretion (TPS) pathway in Gram-negative bacteria consists of a TpsA exoprotein and a cognate TpsB outer membrane pore-forming translocator protein. Previous work has demonstrated that the TpsA protein contains an N-terminal TPS domain that plays an important role in targeting the TpsB protein and is required for secretion. The nontypeable Haemophilus influenzae HMW1 and HMW2 adhesins are homologous proteins that are prototype TpsA proteins and are secreted by the HMW1B and HMW2B TpsB proteins. In the present study, we sought to define the structural determinants of HMW1 interaction with HMW1B during the transport process and while anchored to the bacterial surface. Modeling of HMW1B revealed an N-terminal periplasmic region that contains two polypeptide transport-associated (POTRA) domains and a C-terminal membrane-localized region that forms a pore. Biochemical studies demonstrated that HMW1 engages HMW1B via interaction between the HMW1 TPS domain and the HMW1B periplasmic region, specifically, the predicted POTRA1 and POTRA2 domains. Subsequently, HMW1 is shuttled to the HMW1B pore, facilitated by the N-terminal region, the middle region, and the NPNG motif in the HMW1 TPS domain. Additional analysis revealed that the interaction between HMW1 and HMW1B is highly specific and is dependent upon the POTRA domains and the pore-forming domain of HMW1B. Further studies established that tethering of HMW1 to the surface-exposed region of HMW1B is dependent upon the external loops of HMW1B formed by residues 267 to 283 and residues 324 to 330. These observations may have broad relevance to proteins secreted by the TPS pathway. IMPORTANCE Secretion of HMW1 involves a recognition event between the extended form of the HMW1 propiece and the HMW1B POTRA domains. Our results identify specific interactions between the HMW1 propiece and the periplasmic HMW1B POTRA domains. The results also suggest that the process of HMW1 translocation involves at least two discrete steps, including initial interaction between the HMW1 propiece and the HMW1B POTRA domains and then a separate translocation event. We have also discovered that the HMW1B pore itself appears to influence the translocation process. These observations extend our knowledge of the two-partner secretion system and may be broadly relevant to other proteins secreted by the TPS pathway.
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10
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Garnett JA, Muhl D, Douse CH, Hui K, Busch A, Omisore A, Yang Y, Simpson P, Marchant J, Waksman G, Matthews S, Filloux A. Structure-function analysis reveals that the Pseudomonas aeruginosa Tps4 two-partner secretion system is involved in CupB5 translocation. Protein Sci 2015; 24:670-87. [PMID: 25641651 PMCID: PMC4420518 DOI: 10.1002/pro.2640] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Accepted: 01/07/2015] [Indexed: 01/11/2023]
Abstract
Pseudomonas aeruginosa is a Gram-negative opportunistic bacterium, synonymous with cystic fibrosis patients, which can cause chronic infection of the lungs. This pathogen is a model organism to study biofilms: a bacterial population embedded in an extracellular matrix that provide protection from environmental pressures and lead to persistence. A number of Chaperone-Usher Pathways, namely CupA-CupE, play key roles in these processes by assembling adhesive pili on the bacterial surface. One of these, encoded by the cupB operon, is unique as it contains a nonchaperone-usher gene product, CupB5. Two-partner secretion (TPS) systems are comprised of a C-terminal integral membrane β-barrel pore with tandem N-terminal POTRA (POlypeptide TRansport Associated) domains located in the periplasm (TpsB) and a secreted substrate (TpsA). Using NMR we show that TpsB4 (LepB) interacts with CupB5 and its predicted cognate partner TpsA4 (LepA), an extracellular protease. Moreover, using cellular studies we confirm that TpsB4 can translocate CupB5 across the P. aeruginosa outer membrane, which contrasts a previous observation that suggested the CupB3 P-usher secretes CupB5. In support of our findings we also demonstrate that tps4/cupB operons are coregulated by the RocS1 sensor suggesting P. aeruginosa has developed synergy between these systems. Furthermore, we have determined the solution-structure of the TpsB4-POTRA1 domain and together with restraints from NMR chemical shift mapping and in vivo mutational analysis we have calculated models for the entire TpsB4 periplasmic region in complex with both TpsA4 and CupB5 secretion motifs. The data highlight specific residues for TpsA4/CupB5 recognition by TpsB4 in the periplasm and suggest distinct roles for each POTRA domain.
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Affiliation(s)
- James A Garnett
- Department of Life Sciences, Centre for Structural Biology, Imperial College London, South Kensington Campus, London, SW7 2AZ, United Kingdom; Department of Life Sciences, MRC Centre for Molecular Bacteriology and Infection, Imperial College London, South Kensington Campus, London, SW7 2AZ, United Kingdom
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Norell D, Heuck A, Tran-Thi TA, Götzke H, Jacob-Dubuisson F, Clausen T, Daley DO, Braun V, Müller M, Fan E. Versatile in vitro system to study translocation and functional integration of bacterial outer membrane proteins. Nat Commun 2014; 5:5396. [DOI: 10.1038/ncomms6396] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2014] [Accepted: 09/29/2014] [Indexed: 11/10/2022] Open
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van Ulsen P, Rahman SU, Jong WS, Daleke-Schermerhorn MH, Luirink J. Type V secretion: From biogenesis to biotechnology. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1843:1592-611. [DOI: 10.1016/j.bbamcr.2013.11.006] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2013] [Revised: 11/01/2013] [Accepted: 11/13/2013] [Indexed: 12/13/2022]
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13
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Faure LM, Garvis S, de Bentzmann S, Bigot S. Characterization of a novel two-partner secretion system implicated in the virulence of Pseudomonas aeruginosa. MICROBIOLOGY-SGM 2014; 160:1940-1952. [PMID: 25009238 DOI: 10.1099/mic.0.079616-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Pseudomonas aeruginosa is an opportunistic human pathogen implicated in nosocomial infection and infecting people with compromised immune systems such as cystic fibrosis patients. Although multiple genes involved in P. aeruginosa pathogenesis have been characterized, the overall mechanism of virulence is not fully understood. In this study, we identified a functional two-partner secretion (TPS) system, composed of the PdtA exoprotein and its cognate pore-forming β-barrel PdtB transporter, which is implicated in the virulence of P. aeruginosa. We found that the predicted PdtA exoprotein is related to the HMW-like adhesins subfamily TPS systems. We demonstrate here that limitation of inorganic phosphate (Pi) allows the production of PdtA protein. We show that PdtA is processed during its outer-membrane translocation, with an N-terminal domain released into the extracellular environment and a C-terminal domain associated with the outer membrane of the cell. We also obtained evidence that the transport of PdtA is strictly dependent on the production of PdtB, a result confirming that these proteins constitute a functional TPS system. Furthermore, using the Caenorhabditis elegans model of infection, we show that a pdtA mutant is less virulent than the wild-type strain.
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Affiliation(s)
- Laura M Faure
- UMR7255, CNRS - Aix Marseille Université, 31 Chemin Joseph Aiguier, 13402 Marseille, France
| | - Steve Garvis
- UMR7255, CNRS - Aix Marseille Université, 31 Chemin Joseph Aiguier, 13402 Marseille, France
| | - Sophie de Bentzmann
- UMR7255, CNRS - Aix Marseille Université, 31 Chemin Joseph Aiguier, 13402 Marseille, France
| | - Sarah Bigot
- UMR7255, CNRS - Aix Marseille Université, 31 Chemin Joseph Aiguier, 13402 Marseille, France
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Jacob-Dubuisson F, Guérin J, Baelen S, Clantin B. Two-partner secretion: as simple as it sounds? Res Microbiol 2013; 164:583-95. [PMID: 23542425 DOI: 10.1016/j.resmic.2013.03.009] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2012] [Accepted: 02/05/2013] [Indexed: 10/27/2022]
Abstract
The two-partner secretion (TPS) pathway is a branch of type V secretion. TPS systems are dedicated to the secretion across the outer membrane of long proteins that form extended β-helices. They are composed of a 'TpsA' cargo protein and a 'TpsB' transporter, which belongs to the Omp85 superfamily. This basic design can be supplemented by additional components in some TPS systems. X-ray structures are available for the conserved TPS domain of several TpsA proteins and for one TpsB transporter. However, the molecular mechanisms of two-partner secretion remain to be deciphered, and in particular, the specific role(s) of the TPS domain and the conformational dynamics of the TpsB transporter. Deciphering the TPS pathway may reveal functional features of other transporters of the Omp85 superfamily.
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15
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System specificity of the TpsB transporters of coexpressed two-partner secretion systems of Neisseria meningitidis. J Bacteriol 2012; 195:788-97. [PMID: 23222722 DOI: 10.1128/jb.01355-12] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
The two-partner secretion (TPS) systems of Gram-negative bacteria consist of a large secreted exoprotein (TpsA) and a transporter protein (TpsB) located in the outer membrane. TpsA targets TpsB for transport across the membrane via its ∼30-kDa TPS domain located at its N terminus, and this domain is also the minimal secretory unit. Neisseria meningitidis genomes encode up to five TpsAs and two TpsBs. Sequence alignments of TPS domains suggested that these are organized into three systems, while there are two TpsBs, which raised questions on their system specificity. We show here that the TpsB2 transporter of Neisseria meningitidis is able to secrete all types of TPS domains encoded in N. meningitidis and the related species Neisseria lactamica but not domains of Haemophilus influenzae and Pseudomonas aeruginosa. In contrast, the TpsB1 transporter seemed to be specific for its cognate N. meningitidis system and did not secrete the TPS domains of other meningococcal systems. However, TpsB1 did secrete the TPS2b domain of N. lactamica, which is related to the meningococcal TPS2 domains. Apparently, the secretion depends on specific sequences within the TPS domain rather than the overall TPS domain structure.
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16
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The Burkholderia bcpAIOB genes define unique classes of two-partner secretion and contact dependent growth inhibition systems. PLoS Genet 2012; 8:e1002877. [PMID: 22912595 PMCID: PMC3415462 DOI: 10.1371/journal.pgen.1002877] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2012] [Accepted: 06/15/2012] [Indexed: 11/19/2022] Open
Abstract
Microbes have evolved many strategies to adapt to changes in environmental conditions and population structures, including cooperation and competition. One apparently competitive mechanism is contact dependent growth inhibition (CDI). Identified in Escherichia coli, CDI is mediated by Two-Partner Secretion (TPS) pathway proteins, CdiA and CdiB. Upon cell contact, the toxic C-terminus of the TpsA family member CdiA, called the CdiA-CT, inhibits the growth of CDI(-) bacteria. CDI(+) bacteria are protected from autoinhibition by an immunity protein, CdiI. Bioinformatic analyses indicate that CDI systems are widespread amongst α, β, and γ proteobacteria and that the CdiA-CTs and CdiI proteins are highly variable. CdiI proteins protect against CDI in an allele-specific manner. Here we identify predicted CDI system-encoding loci in species of Burkholderia, Ralstonia and Cupriavidus, named bcpAIOB, that are distinguished from previously-described CDI systems by gene order and the presence of a small ORF, bcpO, located 5' to the gene encoding the TpsB family member. A requirement for bcpO in function of BcpA (the TpsA family member) was demonstrated, indicating that bcpAIOB define a novel class of TPS system. Using fluorescence microscopy and flow cytometry, we show that these genes are expressed in a probabilistic manner during culture of Burkholderia thailandensis in liquid medium. The bcpAIOB genes and extracellular DNA were required for autoaggregation and adherence to an abiotic surface, suggesting that CDI is required for biofilm formation, an activity not previously attributed to CDI. By contrast to what has been observed in E. coli, the B. thailandensis bcpAIOB genes only mediated interbacterial competition on a solid surface. Competition occurred in a defined spatiotemporal manner and was abrogated by allele-specific immunity. Our data indicate that the bcpAIOB genes encode distinct classes of CDI and TPS systems that appear to function in sociomicrobiological community development.
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17
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Leo JC, Grin I, Linke D. Type V secretion: mechanism(s) of autotransport through the bacterial outer membrane. Philos Trans R Soc Lond B Biol Sci 2012; 367:1088-101. [PMID: 22411980 PMCID: PMC3297439 DOI: 10.1098/rstb.2011.0208] [Citation(s) in RCA: 172] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Autotransport in Gram-negative bacteria denotes the ability of surface-localized proteins to cross the outer membrane (OM) autonomously. Autotransporters perform this task with the help of a β-barrel transmembrane domain localized in the OM. Different classes of autotransporters have been investigated in detail in recent years; classical monomeric but also trimeric autotransporters comprise many important bacterial virulence factors. So do the two-partner secretion systems, which are a special case as the transported protein resides on a different polypeptide chain than the transporter. Despite the great interest in these proteins, the exact mechanism of the transport process remains elusive. Moreover, different periplasmic and OM factors have been identified that play a role in the translocation, making the term ‘autotransport’ debatable. In this review, we compile the wealth of details known on the mechanism of single autotransporters from different classes and organisms, and put them into a bigger perspective. We also discuss recently discovered or rediscovered classes of autotransporters.
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Affiliation(s)
- Jack C Leo
- Max Planck Institute for Developmental Biology, Spemannstrasse 35, 72076 Tübingen, Germany
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18
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Delattre A, Saint N, Clantin B, Willery E, Lippens G, Locht C, Villeret V, Jacob‐Dubuisson F. Substrate recognition by the POTRA domains of TpsB transporter FhaC. Mol Microbiol 2011; 81:99-112. [DOI: 10.1111/j.1365-2958.2011.07680.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Anne‐Sophie Delattre
- Inserm U1019, Center for Infection and Immunity of Lille, F‐59019 Lille, France
- Institut Pasteur de Lille, F‐59019 Lille, France
- Univ Lille Nord de France, F‐59000 Lille, France
- CNRS UMR8204, F‐59021 Lille, France
| | - Nathalie Saint
- INSERM U1046, Université de Montpellier 1 et 2, F‐34090 Montpellier cedex, France
| | - Bernard Clantin
- CNRS USR3078, Institut de Recherche Interdisciplinaire – Université de Lille 1 – Université de Lille 2, F‐59658 Villeneuve d'Ascq, France
| | - Eve Willery
- Inserm U1019, Center for Infection and Immunity of Lille, F‐59019 Lille, France
- Institut Pasteur de Lille, F‐59019 Lille, France
- Univ Lille Nord de France, F‐59000 Lille, France
- CNRS UMR8204, F‐59021 Lille, France
| | - Guy Lippens
- CNRS UMR 8576 – Université de Lille I, F‐59655 Villeneuve d'Ascq – France
| | - Camille Locht
- Inserm U1019, Center for Infection and Immunity of Lille, F‐59019 Lille, France
- Institut Pasteur de Lille, F‐59019 Lille, France
- Univ Lille Nord de France, F‐59000 Lille, France
- CNRS UMR8204, F‐59021 Lille, France
| | - Vincent Villeret
- CNRS USR3078, Institut de Recherche Interdisciplinaire – Université de Lille 1 – Université de Lille 2, F‐59658 Villeneuve d'Ascq, France
| | - Françoise Jacob‐Dubuisson
- Inserm U1019, Center for Infection and Immunity of Lille, F‐59019 Lille, France
- Institut Pasteur de Lille, F‐59019 Lille, France
- Univ Lille Nord de France, F‐59000 Lille, France
- CNRS UMR8204, F‐59021 Lille, France
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19
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Schielke S, Frosch M, Kurzai O. Virulence determinants involved in differential host niche adaptation of Neisseria meningitidis and Neisseria gonorrhoeae. Med Microbiol Immunol 2010; 199:185-96. [PMID: 20379743 DOI: 10.1007/s00430-010-0150-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2010] [Indexed: 11/28/2022]
Abstract
Neisseria meningitidis and Neisseria gonorrhoeae are the only pathogenic species of the genus Neisseria. Although these two species are closely related, they specialized on survival in completely different environments within the human host-the nasopharynx in the case of N. meningitidis versus the urogenital tract in the case of N. gonorrhoeae. The genetic background of these differences has not yet been determined. Here, we present a comparison of all characterized transcriptional regulators in these species, delineating analogous functions and disclosing differential functional developments of these DNA-binding proteins with a special focus on the recently characterized regulator FarR and its contribution to divergent host niche adaptation in the two Neisseria spp. Furthermore, we summarize the present knowledge on two-partner secretion systems in meningococci, highlighting their overall expression among meningococcal strains in contrast to the complete absence in gonococci. Concluding, the decisive role of these two entirely different factors in host niche adaptation of the two human pathogenic Neisseria species is depicted, illuminating another piece of the puzzle to locate the molecular basis of their differences in preferred colonization sites and pathogenicity.
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Affiliation(s)
- Stephanie Schielke
- Institute of Hygiene and Microbiology, University of Würzburg, Würzburg, Germany
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20
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Choi PS, Bernstein HD. Sequential translocation of an Escherchia coli two-partner secretion pathway exoprotein across the inner and outer membranes. Mol Microbiol 2010; 75:440-51. [PMID: 19968793 PMCID: PMC3107007 DOI: 10.1111/j.1365-2958.2009.06993.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
In Gram-negative bacteria, a variety of high molecular weight 'exoproteins' are translocated across the outer membrane (OM) via the two-partner secretion (TPS) pathway by interacting with a dedicated transporter. It is unclear, however, whether the translocation of exoproteins across the OM is coupled to their translocation across the inner membrane (IM). To address this question, we separated the production of an Escherichia coli O157:H7 exoprotein (OtpA) and its transporter (OtpB) temporally by placing otpA and otpB under the control of distinct regulatable promoters. We found that when both full-length and truncated forms of OtpA were expressed prior to OtpB, a significant fraction of the exoprotein was secreted. The results indicate that OtpA can be translocated into the periplasm and briefly remain secretion-competent. Furthermore, by engineering cysteine residues into OtpA and using disulphide bond formation as a reporter of periplasmic localization, we obtained additional evidence that the C-terminus of OtpA enters the periplasm before the N-terminus is translocated across the OM even when OtpA and OtpB are expressed simultaneously. Taken together, our results demonstrate that the translocation of a TPS exoprotein across the OM can occur independently from its translocation across the IM.
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Affiliation(s)
- Peter S. Choi
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-0538, USA
| | - Harris D. Bernstein
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-0538, USA
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21
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Abstract
Bacterial toxins damage the host at the site of bacterial infection or distant from the site. Bacterial toxins can be single proteins or oligomeric protein complexes that are organized with distinct AB structure-function properties. The A domain encodes a catalytic activity. ADP ribosylation of host proteins is the earliest post-translational modification determined to be performed by bacterial toxins; other modifications include glucosylation and proteolysis. Bacterial toxins also catalyze the non-covalent modification of host protein function or can modify host cell properties through direct protein-protein interactions. The B domain includes two functional domains: a receptor-binding domain, which defines the tropism of a toxin for a cell and a translocation domain that delivers the A domain across a lipid bilayer, either on the plasma membrane or the endosome. Bacterial toxins are often characterized based upon the secretion mechanism that delivers the toxin out of the bacterium, termed types I-VII. This review summarizes the major families of bacterial toxins and also describes the specific structure-function properties of the botulinum neurotoxins.
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Affiliation(s)
- James S Henkel
- Medical College of Wisconsin, Department of Microbiology and Molecular Genetics, Milwaukee, WI 53151, USA.
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22
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Saier MH, Ma CH, Rodgers L, Tamang DG, Yen MR. Protein secretion and membrane insertion systems in bacteria and eukaryotic organelles. ADVANCES IN APPLIED MICROBIOLOGY 2009; 65:141-97. [PMID: 19026865 DOI: 10.1016/s0065-2164(08)00606-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- Milton H Saier
- Division of Biological Sciences, University of California at San Diego, La Jolla, California 92093-0116, USA
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23
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Julio SM, Inatsuka CS, Mazar J, Dieterich C, Relman DA, Cotter PA. Natural-host animal models indicate functional interchangeability between the filamentous haemagglutinins of Bordetella pertussis and Bordetella bronchiseptica and reveal a role for the mature C-terminal domain, but not the RGD motif, during infection. Mol Microbiol 2009; 71:1574-90. [PMID: 19220744 DOI: 10.1111/j.1365-2958.2009.06623.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Bacteria of the Bordetella genus cause respiratory tract infections. Both broad host range (e.g. Bordetella bronchiseptica) and human-adapted (e.g. Bordetella pertussis) strains produce a surface-exposed and secreted protein called filamentous haemagglutinin (FHA) that functions in adherence and immunomodulation. Previous studies using B. pertussis and cultured mammalian cells identified several FHA domains with potential roles in host cell interactions, including an Arg-Gly-Asp (RGD) triplet that was reported to bind integrins on epithelial cells and monocytes to activate host signalling pathways. We show here that, in contrast to our previous report, the fhaB genes of B. pertussis and B. bronchiseptica are functionally interchangeable, at least with regard to the various in vitro and in vivo assays investigated. This result is significant because it indicates that information obtained studying FHA using B. bronchiseptica and natural-host animal models should apply to B. pertussis FHA as well. We also show that the C-terminus of mature FHA, which we name the MCD, mediates adherence to epithelial and macrophage-like cells and is required for colonization of the rat respiratory tract and modulation of the inflammatory response in mouse lungs. We could not, however, detect a role for the RGD in any of these processes.
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Affiliation(s)
- Steven M Julio
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA 93106-9610, USA
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24
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Gottig N, Garavaglia BS, Garofalo CG, Orellano EG, Ottado J. A filamentous hemagglutinin-like protein of Xanthomonas axonopodis pv. citri, the phytopathogen responsible for citrus canker, is involved in bacterial virulence. PLoS One 2009; 4:e4358. [PMID: 19194503 PMCID: PMC2632755 DOI: 10.1371/journal.pone.0004358] [Citation(s) in RCA: 117] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2008] [Accepted: 12/29/2008] [Indexed: 11/19/2022] Open
Abstract
Xanthomonas axonopodis pv. citri, the phytopathogen responsible for citrus canker has a number of protein secretion systems and among them, at least one type V protein secretion system belonging to the two-partner secretion pathway. This system is mainly associated to the translocation of large proteins such as adhesins to the outer membrane of several pathogens. Xanthomonas axonopodis pv. citri possess a filamentous hemagglutinin-like protein in close vicinity to its putative transporter protein, XacFhaB and XacFhaC, respectively. Expression analysis indicated that XacFhaB was induced in planta during plant-pathogen interaction. By mutation analysis of XacFhaB and XacFhaC genes we determined that XacFhaB is involved in virulence both in epiphytic and wound inoculations, displaying more dispersed and fewer canker lesions. Unexpectedly, the XacFhaC mutant in the transporter protein produced an intermediate virulence phenotype resembling wild type infection, suggesting that XacFhaB could be secreted by another partner different from XacFhaC. Moreover, XacFhaB mutants showed a general lack of adhesion and were affected in leaf surface attachment and biofilm formation. In agreement with the in planta phenotype, adhesin lacking cells moved faster in swarming plates. Since no hyperflagellation phenotype was observed in this bacteria, the faster movement may be attributed to the lack of cell-to-cell aggregation. Moreover, XacFhaB mutants secreted more exopolysaccharide that in turn may facilitate its motility. Our results suggest that this hemagglutinin-like protein is required for tissue colonization being mainly involved in surface attachment and biofilm formation, and that plant tissue attachment and cell-to-cell aggregation are dependent on the coordinated action of adhesin molecules and exopolysaccharides.
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Affiliation(s)
- Natalia Gottig
- Molecular Biology Division, Instituto de Biología Molecular y Celular de Rosario, Consejo Nacional de Investigaciones Científicas y Técnicas, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina
| | - Betiana S. Garavaglia
- Molecular Biology Division, Instituto de Biología Molecular y Celular de Rosario, Consejo Nacional de Investigaciones Científicas y Técnicas, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina
| | - Cecilia G. Garofalo
- Molecular Biology Division, Instituto de Biología Molecular y Celular de Rosario, Consejo Nacional de Investigaciones Científicas y Técnicas, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina
| | - Elena G. Orellano
- Molecular Biology Division, Instituto de Biología Molecular y Celular de Rosario, Consejo Nacional de Investigaciones Científicas y Técnicas, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina
| | - Jorgelina Ottado
- Molecular Biology Division, Instituto de Biología Molecular y Celular de Rosario, Consejo Nacional de Investigaciones Científicas y Técnicas, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina
- * E-mail:
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25
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Newman CL, Stathopoulos C. Autotransporter and Two-Partner Secretion: Delivery of Large-Size Virulence Factors by Gram-Negative Bacterial Pathogens. Crit Rev Microbiol 2008; 30:275-86. [PMID: 15646401 DOI: 10.1080/10408410490499872] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
A number of protein secretion mechanisms have been identified in gram-negative pathogens. Many of these secretion systems are dependent upon the Sec translocase for protein export from the cytoplasm into the periplasm and then utilize other mechanisms for transport from the periplasm through the outer membrane. In this article, we review secretion similarities between autotransporter and two-partner secretion systems, and we report similarities between the autotransporter secretion mechanism with that of intimin/invasins. Considering that many secreted proteins are virulence factors, a better understanding of their secretion mechanisms will aid in the development of disease treatments and new bacterial vaccines.
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Affiliation(s)
- Cheryl L Newman
- Department of Biology & Biochemistry, University of Houston, Houston, Texas 77204, USA
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26
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Two-partner secretion systems of Neisseria meningitidis associated with invasive clonal complexes. Infect Immun 2008; 76:4649-58. [PMID: 18678657 DOI: 10.1128/iai.00393-08] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The two-partner secretion (TPS) pathway is widespread among gram-negative bacteria and facilitates the secretion of very large and often virulence-related proteins. TPS systems consist of a secreted TpsA protein and a TpsB protein involved in TpsA transport across the outer membrane. Sequenced Neisseria meningitidis genomes contain up to five TpsA- and two TpsB-encoding genes. Here, we investigated the distribution of TPS-related open reading frames in a collection of disease isolates. Three distinct TPS systems were identified among meningococci. System 1 was ubiquitous, while systems 2 and 3 were significantly more prevalent among isolates of hyperinvasive clonal complexes than among isolates of poorly invasive clonal complexes. In laboratory cultures, systems 1 and 2 were expressed. However, several sera from patients recovering from disseminated meningococcal disease recognized the TpsAs of systems 2 and 3, indicating the expression of these systems during infection. Furthermore, we showed that the major secreted TpsAs of systems 1 and 2 depend on their cognate TpsBs for transport across the outer membrane and that the system 1 TpsAs undergo processing. Together, our data indicate that TPS systems may contribute to the virulence of N. meningitidis.
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27
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Mazar J, Cotter PA. New insight into the molecular mechanisms of two-partner secretion. Trends Microbiol 2007; 15:508-15. [DOI: 10.1016/j.tim.2007.10.005] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2007] [Revised: 08/15/2007] [Accepted: 10/25/2007] [Indexed: 12/29/2022]
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28
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Schmitt C, Turner D, Boesl M, Abele M, Frosch M, Kurzai O. A functional two-partner secretion system contributes to adhesion of Neisseria meningitidis to epithelial cells. J Bacteriol 2007; 189:7968-76. [PMID: 17873034 PMCID: PMC2168671 DOI: 10.1128/jb.00851-07] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Neisseria meningitidis is a frequent commensal of the human nasopharynx causing severe invasive infections in rare cases. A functional two-partner secretion (TPS) system in N. meningitidis, composed of the secreted effector protein HrpA and its cognate transporter HrpB, is identified and characterized in this study. Although all meningococcal strains harbor at least one TPS system, the hrpA genes display significant C-terminal sequence variation. Meningococcal genes encoding the TPS effector proteins and their transporters are closely associated and transcribed into a single mRNA. HrpA proteins are translocated across the meningococcal outer membrane by their cognate transporters HrpB and mainly released into the environment. During this process, HrpA is proteolytically processed to a mature 180-kDa form. In contrast to other known TPS systems, immature HrpA proteins are stable in the absence of HrpB and accumulate within the bacterial cell. A small percentage of mature HrpA remains associated with the bacteria and contributes to the interaction of meningococci with epithelial cells.
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Affiliation(s)
- Corinna Schmitt
- University of Wuerzburg, Institute of Hygiene and Microbiology, Josef-Schneider-Str. 2, E1, 97080 Wuerzburg, Germany
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29
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Saier MH. Protein Secretion and Membrane Insertion Systems in Gram-Negative Bacteria. J Membr Biol 2007; 214:75-90. [PMID: 17546510 DOI: 10.1007/s00232-006-0049-7] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2006] [Revised: 11/07/2006] [Indexed: 12/30/2022]
Abstract
In contrast to other organisms, gram-negative bacteria have evolved numerous systems for protein export. Eight types are known that mediate export across or insertion into the cytoplasmic membrane, while eight specifically mediate export across or insertion into the outer membrane. Three of the former secretory pathway (SP) systems, type I SP (ISP, ABC), IIISP (Fla/Path) and IVSP (Conj/Vir), can export proteins across both membranes in a single energy-coupled step. A fourth generalized mechanism for exporting proteins across the two-membrane envelope in two distinct steps (which we here refer to as type II secretory pathways [IISP]) utilizes either the general secretory pathway (GSP or Sec) or the twin-arginine targeting translocase for translocation across the inner membrane, and either the main terminal branch or one of several protein-specific export systems for translocation across the outer membrane. We here survey the various well-characterized protein translocation systems found in living organisms and then focus on the systems present in gram-negative bacteria. Comparisons between these systems suggest specific biogenic, mechanistic and evolutionary similarities as well as major differences.
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Affiliation(s)
- Milton H Saier
- Division of Biological Sciences, University of California at San Diego, La Jolla, CA 92093-0116, USA.
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30
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Choi PS, Dawson AJ, Bernstein HD. Characterization of a novel two-partner secretion system in Escherichia coli O157:H7. J Bacteriol 2007; 189:3452-61. [PMID: 17322314 PMCID: PMC1855909 DOI: 10.1128/jb.01751-06] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Gram-negative bacteria contain multiple secretion pathways that facilitate the translocation of proteins across the outer membrane. The two-partner secretion (TPS) system is composed of two essential components, a secreted exoprotein and a pore-forming beta barrel protein that is thought to transport the exoprotein across the outer membrane. A putative TPS system was previously described in the annotation of the genome of Escherichia coli O157:H7 strain EDL933. We found that the two components of this system, which we designate OtpA and OtpB, are not predicted to belong to either of the two major subtypes of TPS systems (hemolysins and adhesins) based on their sequences. Nevertheless, we obtained direct evidence that OtpA and OtpB constitute a bona fide TPS system. We found that secretion of OtpA into the extracellular environment in E. coli O157:H7 requires OtpB and that when OtpA was produced in an E. coli K-12 strain, its secretion was strictly dependent on the production of OtpB. Furthermore, using OtpA/OtpB as a model system, we show that protein secretion via the TPS pathway is extremely rapid.
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Affiliation(s)
- Peter S Choi
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-0538, USA
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Winter LE, Barenkamp SJ. Antibodies specific for the high-molecular-weight adhesion proteins of nontypeable Haemophilus influenzae are opsonophagocytic for both homologous and heterologous strains. CLINICAL AND VACCINE IMMUNOLOGY : CVI 2006; 13:1333-42. [PMID: 17021246 PMCID: PMC1694446 DOI: 10.1128/cvi.00221-06] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The HMW1/HMW2-like adhesion proteins of nontypeable Haemophilus influenzae (NTHI) are expressed by 75% of NTHI strains. Antibodies directed against these proteins are opsonophagocytic in vitro and are protective in an animal model of infection. The objective of the present study was to determine the opsonophagocytic activity of high-titer anti-HMW1/HMW2 immune sera against both homologous and heterologous NTHI strains. Chinchillas were immunized with purified HMW1/HMW2-like proteins from five prototype NTHI strains. Serum opsonophagocytic activity was monitored in an assay that uses a human promyelocytic cell line, HL-60, as the source of phagocytic cells. Preimmune sera did not demonstrate opsonophagocytic killing of any strains. In contrast, the immune sera demonstrated killing of the five homologous NTHI strains at titers ranging from 1:320 to 1:640. The immune sera also demonstrated killing of eight heterologous NTHI strains that express HMW1/HMW2-like proteins at titers ranging from 0 to 1:640. Killing of heterologous strains sometimes demonstrated a prozone phenomenon. None of the immune sera killed NTHI strains that did not express HMW1/HMW2-like proteins. Adsorption of immune sera with HMW1/HMW2-like proteins purified from either homologous or heterologous NTHI strains eliminated opsonophagocytic killing of homologous strains in most cases. These data demonstrate that antibodies produced following immunization with the HMW1/HMW2-like proteins are opsonophagocytic for both homologous and heterologous NTHI and strongly suggest that common epitopes recognized by functionally active antibodies exist on the HMW1/HMW2-like proteins of unrelated NTHI strains. The results argue for the continued investigation of the HMW1/HMW2-like proteins as potential vaccine candidates for the prevention of NTHI disease.
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Affiliation(s)
- Linda E Winter
- Department of Pediatrics, St. Louis University School of Medicine, Saint Louis, MO 63104-1095, USA
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Mazar J, Cotter PA. Topology and maturation of filamentous haemagglutinin suggest a new model for two‐partner secretion. Mol Microbiol 2006; 62:641-54. [PMID: 16999837 DOI: 10.1111/j.1365-2958.2006.05392.x] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Two-partner secretion (TPS) is the most widely distributed secretion pathway known. These systems export large exoproteins through highly conserved channel-forming beta-barrel proteins. Filamentous haemagglutinin (FHA), expressed by Bordetella species, is the prototypical TPS family member. Here we show that the C-terminus of mature FHA, as opposed to the N-terminus as previously proposed, is exposed on the cell surface and is required for mediating adherence to cultured epithelial cells. We show that the C-terminus of the FHA pro-protein (FhaB) is required for FHA function in vitro and in vivo and we show that cleavage of FhaB to form FHA is not the mechanism by which FHA is released from the cell. Based on these data, we propose a new model for TPS. This model provides an explanation for the energetics of export of globular protein domains across membranes in the absence of ATP and it suggests a new mechanism for the control of protein folding.
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Affiliation(s)
- Joseph Mazar
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, CA 93106-9610, USA
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Schleiff E, Soll J. Membrane protein insertion: mixing eukaryotic and prokaryotic concepts. EMBO Rep 2006; 6:1023-7. [PMID: 16264426 PMCID: PMC1371041 DOI: 10.1038/sj.embor.7400563] [Citation(s) in RCA: 112] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2005] [Accepted: 09/22/2005] [Indexed: 11/09/2022] Open
Abstract
Proteins are translocated across or inserted into membranes by machines that are composed of soluble and membrane-anchored subunits. The molecular action of these machines and their evolutionary origin are at present the focus of intense research. For instance, our understanding of the mode of insertion of beta-barrel membrane proteins into the outer membrane of endosymbiotically derived organelles has increased rapidly during the past few years. In particular, the identification of the Omp85/YaeT-involving pathways in Neisseria meningitidis, Escherichia coli and cyanobacteria, and homologues of Omp85/YaeT in chloroplasts and mitochondria, has provided new clues about the ancestral beta-barrel protein insertion pathway. This review focuses on recent advances in the elucidation of the evolutionarily conserved concepts that underlie the translocation and insertion of beta-barrel membrane proteins.
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Affiliation(s)
- Enrico Schleiff
- Department of Biology I, Ludwig-Maximilians-Universität Munich, Menzinger Strasse 67, 80638 Munich, Germany.
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Hodak H, Clantin B, Willery E, Villeret V, Locht C, Jacob-Dubuisson F. Secretion signal of the filamentous haemagglutinin, a model two-partner secretion substrate. Mol Microbiol 2006; 61:368-82. [PMID: 16771844 DOI: 10.1111/j.1365-2958.2006.05242.x] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The sorting of proteins to their proper subcellular compartment requires specific addressing signals that mediate interactions with ad hoc transport machineries. In Gram-negative bacteria, the widespread two-partner secretion (TPS) pathway is dedicated to the secretion of large, mostly virulence-related proteins. The secreted TpsA proteins carry a characteristic 250-residue-long N-terminal 'TPS domain' essential for secretion, while their TpsB transporters are pore-forming proteins that specifically recognize their respective TpsA partners and mediate their translocation across the outer membrane. However, the nature of the secretion signal has not been elucidated yet. The whooping cough agent Bordetella pertussis secretes its major adhesin filamentous haemagglutinin (FHA) via the TpsB transporter FhaC. In this work, we show specific interactions between an N-terminal fragment of FHA containing the TPS domain and FhaC by using two different techniques, an overlay assay and a pull-down of the complex. FhaC recognizes only non-native conformations of the TPS domain, corroborating the model that in vivo, periplasmic FHA is not yet folded. By generating single amino acid substitutions, we have identified interaction determinants forming the secretion signal. They are found unexpectedly far into the TPS domain and include both conserved and variable residues, which most likely explains the specificity of the TpsA-TpsB interaction. The N-terminal domain of FhaC is involved in the FHA-FhaC interaction, in agreement with its proposed function and periplasmic localization.
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Affiliation(s)
- Hélène Hodak
- INSERM U629, 1 rue Calmette, F-59019 Lille Cedex, France
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Surana NK, Buscher AZ, Hardy GG, Grass S, Kehl-Fie T, St Geme JW. Translocator Proteins in the Two-partner Secretion Family Have Multiple Domains. J Biol Chem 2006; 281:18051-8. [PMID: 16648638 DOI: 10.1074/jbc.m600036200] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The two-partner secretion pathway in Gram-negative bacteria consists of a TpsA exoprotein and a cognate TpsB outer membrane translocator protein. Previous work has demonstrated that the TpsB protein forms a beta-barrel structure with pore forming activity and facilitates translocation of the TpsA protein across the outer membrane. In this study, we characterized the functional domains of the Haemophilus influenzae HMW1B protein, a TpsB protein that interacts with the H. influenzae HMW1 adhesin. Using c-Myc epitope tag insertions and cysteine substitution mutagenesis, we discovered that HMW1B contains an N-terminal surface-localized domain, an internal periplasmic domain, and a C-terminal membrane anchor. Functional and biochemical analysis of the c-Myc epitope tag insertions and a series of HMW1B deletion constructs demonstrated that the periplasmic domain is required for secretion of HMW1 and that the C-terminal membrane anchor (HMW1B-(234-545)) is capable of oligomerization and pore formation. Similar to our observations with HMW1B, examination of a Bordetella pertussis TpsB protein called FhaC revealed that the C terminus of FhaC (FhaC-(232-585)) is capable of pore formation. We speculate that all TpsB proteins have a modular structure, with a periplasmic domain that interacts with the cognate TpsA protein and with pore forming activity contained within the C terminus.
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Affiliation(s)
- Neeraj K Surana
- The Edward Mallinckrodt Department of Pediatrics and the Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110, USA
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van Ulsen P, Tommassen J. Protein secretion and secreted proteins in pathogenicNeisseriaceae. FEMS Microbiol Rev 2006; 30:292-319. [PMID: 16472308 DOI: 10.1111/j.1574-6976.2006.00013.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
Secreted proteins of pathogenic bacteria are often essential virulence factors. They are involved, for example, in the adherence of the bacteria to host cells or required to suppress the host's defence mechanisms. Until recently, only IgA1 protease had been studied in detail in the NeisseriaceaeNeisseria meningitidis and Neisseria gonorrhoeae. The availability of their genome sequences, however, has boosted research in this area. Here, we present a survey of the secretome of the pathogenic Neisseriaceae, based on the available genome sequences, and the current knowledge of the functions and structures of the secreted proteins. Of the six protein-secretion pathways that are widely disseminated among Gram-negative bacteria, three pathways appear to be present among the Neisseriaceae, i.e. the autotransporter-, the two-partner- and the type I-secretion mechanisms. Comparison of the predicted secretomes reveals a considerable flexibility. As compared with N. meningitidis and the nonpathogen N. lactamica, N. gonorrhoeae appears to have a considerably degenerated secretome, which may reflect its altered niche occupancy. The flexibility of the secretome may be enhanced by the presence of ORFs in the genomes potentially encoding fragments of secreted proteins. We hypothesize that these ORFs may substitute for the corresponding fragments in the full-length genes through genetic recombination, thereby changing the host-cell receptor specificity of the secreted protein.
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Affiliation(s)
- Peter van Ulsen
- Department of Molecular Microbiology and Institute of Biomembranes, Utrecht University, Utrecht, The Netherlands
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Abstract
Omp85 is a protein found in Gram-negative bacteria where it serves to integrate proteins into the bacterial outer membrane. Members of the Omp85 family of proteins are defined by the presence of two domains: an N-terminal, periplasmic domain rich in POTRA repeats and a C-terminal beta-barrel domain embedded in the outer membrane. The widespread distribution of Omp85 family members together with their fundamental role in outer membrane assembly suggests the ancestral Omp85 arose early in the evolution of prokaryotic cells. Mitochondria, derived from an ancestral bacterial endosymbiont, also use a member of the Omp85 family to assemble proteins in their outer membranes. More distant relationships are seen between the Omp85 family and both the core proteins in two-partner secretion systems and the Toc75 family of protein translocases found in plastid outer envelopes. Aspects of the ancestry and molecular architecture of the Omp85 family of proteins is providing insight into the mechanism by which proteins might be integrated and assembled into bacterial outer membranes.
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Affiliation(s)
- Ian E Gentle
- Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville 3010, Australia
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38
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Julio SM, Cotter PA. Characterization of the filamentous hemagglutinin-like protein FhaS in Bordetella bronchiseptica. Infect Immun 2005; 73:4960-71. [PMID: 16041011 PMCID: PMC1201180 DOI: 10.1128/iai.73.8.4960-4971.2005] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Filamentous hemagglutinin (FHA) is a large (>200 kDa), rod-shaped protein expressed by bordetellae that is both surface-associated and secreted. FHA mediates bacterial adherence to epithelial cells and macrophages in vitro and is absolutely required for tracheal colonization in vivo. The recently sequenced Bordetella bronchiseptica genome revealed the presence of a gene, fhaS, that is nearly identical to fhaB, the FHA structural gene. We show that although fhaS expression requires the BvgAS virulence control system, it is maximal only under a subset of conditions in which BvgAS is active, suggesting an additional level of regulation. We also show that, like FHA, FhaS undergoes a C-terminal proteolytic processing event and is both surface-associated and secreted and that export across the outer membrane requires the channel-forming protein FhaC. Unlike FHA, however, FhaS was unable to mediate adherence of B. bronchiseptica to epithelial cell lines in vitro and was not required for respiratory tract colonization in vivo. In a coinfection experiment, a DeltafhaS strain was out-competed by wild-type B. bronchiseptica, indicating that fhaS is expressed in vivo and that FhaS contributes to bacterial fitness in a manner revealed when the mutant must compete with wild-type bacteria. These data suggest that FHA and FhaS perform distinct functions during the Bordetella infectious cycle. A survey of various Bordetella strains revealed two distinct fhaS alleles that segregate according to pathogen host range and that B. parapertussis(hu) most likely acquired its fhaS allele from B. pertussis horizontally, suggesting fhaS may contribute to host-species specificity.
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Affiliation(s)
- Steven M Julio
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA 93106-9610, USA
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Moslavac S, Mirus O, Bredemeier R, Soll J, von Haeseler A, Schleiff E. Conserved pore-forming regions in polypeptide-transporting proteins. FEBS J 2005; 272:1367-78. [PMID: 15752354 DOI: 10.1111/j.1742-4658.2005.04569.x] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Transport of solutes and polypeptides across membranes is an essential process for every cell. In the past, much focus has been placed on helical transporters. Recently, the beta-barrel-shaped transporters have also attracted some attention. The members of this family are found in the outer bacterial membrane and the outer membrane of endosymbiotically derived organelles. Here we analyze the features and the evolutionary development of a specified translocator family, namely the beta-barrel-shaped polypeptide-transporters. We identified sequence motifs, which characterize all transporters of this family, as well as motifs specific for a certain subgroup of proteins of this class. The general motifs are related to the structural composition of the pores. Further analysis revealed a defined distance of two motifs to the C-terminal portion of the proteins. Furthermore, the evolutionary relationship of the proteins and the motifs are discussed.
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Protein secretion through autotransporter and two-partner pathways. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2005; 1694:235-57. [PMID: 15546669 DOI: 10.1016/j.bbamcr.2004.03.008] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2003] [Revised: 03/18/2004] [Accepted: 03/26/2004] [Indexed: 01/19/2023]
Abstract
Two distinct protein secretion pathways, the autotransporter (AT) and the two-partner secretion (TPS) pathways are characterized by their apparent simplicity. Both are devoted to the translocation across the outer membrane of mostly large proteins or protein domains. As implied by their name, AT proteins contain their own transporter domain, covalently attached to the C-terminal extremity of the secreted passenger domain, while TPS systems are composed of two separate proteins, with TpsA being the secreted protein and TpsB its specific transporter. In both pathways, the secreted proteins are exported in a Sec-dependent manner across the inner membrane, after which they cross the outer membrane with the help of their cognate transporters. The AT translocator domains and the TpsB proteins constitute distinct families of protein-translocating, outer membrane porins of Gram-negative bacteria. Both types of transporters insert into the outer membrane as beta-barrel proteins possibly forming oligomeric pores in the case of AT and serve as conduits for their cognate secreted proteins or domains across the outer membrane. Translocation appears to be folding-sensitive in both pathways, indicating that AT passenger domains and TpsA proteins cross the periplasm and the outer membrane in non-native conformations and fold progressively at the cell surface. A major difference between AT and TPS pathways arises from the manner by which specificity is established between the secreted protein and its transporter. In AT, the covalent link between the passenger and the translocator domains ensures the translocation of the former without the need for a specific molecular recognition between the two modules. In contrast, the TPS pathway has solved the question of specific recognition between the TpsA proteins and their transporters by the addition to the TpsA proteins of an N-proximal module, the conserved TPS domain, which represents a hallmark of the TPS pathway.
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Henderson IR, Navarro-Garcia F, Desvaux M, Fernandez RC, Ala'Aldeen D. Type V protein secretion pathway: the autotransporter story. Microbiol Mol Biol Rev 2004; 68:692-744. [PMID: 15590781 PMCID: PMC539010 DOI: 10.1128/mmbr.68.4.692-744.2004] [Citation(s) in RCA: 595] [Impact Index Per Article: 29.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Gram-negative bacteria possess an outer membrane layer which constrains uptake and secretion of solutes and polypeptides. To overcome this barrier, bacteria have developed several systems for protein secretion. The type V secretion pathway encompasses the autotransporter proteins, the two-partner secretion system, and the recently described type Vc or AT-2 family of proteins. Since its discovery in the late 1980s, this family of secreted proteins has expanded continuously, due largely to the advent of the genomic age, to become the largest group of secreted proteins in gram-negative bacteria. Several of these proteins play essential roles in the pathogenesis of bacterial infections and have been characterized in detail, demonstrating a diverse array of function including the ability to condense host cell actin and to modulate apoptosis. However, most of the autotransporter proteins remain to be characterized. In light of new discoveries and controversies in this research field, this review considers the autotransporter secretion process in the context of the more general field of bacterial protein translocation and exoprotein function.
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Affiliation(s)
- Ian R Henderson
- Division of Immunity and Infection, University of Birmingham, Birmingham B15 2TT, UK.
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42
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Brown NF, Logue CA, Boddey JA, Scott R, Hirst RG, Beacham IR. Identification of a novel two-partner secretion system from Burkholderia pseudomallei. Mol Genet Genomics 2004; 272:204-15. [PMID: 15316770 DOI: 10.1007/s00438-004-1039-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2003] [Accepted: 06/22/2004] [Indexed: 10/26/2022]
Abstract
Two adjacent genes, bpaA and bpaB, whose products display significant similarity to a number of two-partner secretion (TPS) systems have been identified in Burkholderia pseudomallei strain 08, but are absent from the closely related avirulent species B. thailandensis. They possess a number of sequence features characteristic of TPS systems, including the presence of an NPNGI motif in a region of BpaA which strongly resembles a TPS secretion domain. BpaA is a very large protein (approximately 530 kDa) and contains three repeats, each 600-800-amino acids long. Putative membrane-spanning regions in BpaB were identified through alignment with TpsB family members, and this also revealed an N-terminal extension not found in other TpsB proteins. The bpaA gene was found to be absent from the majority of B. pseudomallei strains. It appears that bpaAB are located within a putative genomic island that is inserted in close proximity to a methionine tRNA(CAT)-encoding gene. Expression of BpaA was undetectable in cells grown in laboratory media. However, owing to the similarity of BpaA to known adhesin molecules, a potential role of BpaA in virulence was investigated in cell culture and in an animal model, but no evidence for such a role was found in these test systems.
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Affiliation(s)
- N F Brown
- School of Health Science, Griffith University-Gold Coast Campus, PMB 50 Gold Coast Mail Centre, QLD 4217, Gold Coast, Queensland, Australia
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Desvaux M, Parham NJ, Henderson IR. The autotransporter secretion system. Res Microbiol 2004; 155:53-60. [PMID: 14990256 DOI: 10.1016/j.resmic.2003.10.002] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2003] [Accepted: 10/03/2003] [Indexed: 01/13/2023]
Abstract
The type V secretion system includes the autotransporter family, the two-partner system and the Oca family. The autotransporter secretion process involving first the translocation of the precursor through the inner membrane and then its translocation through the outer membrane via a pore formed by a beta-barrel is reviewed.
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Affiliation(s)
- Mickaël Desvaux
- Bacterial Pathogenesis and Genomics Unit, Division of Immunity and Infection, The Medical School, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
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Ward CK, Mock JR, Hansen EJ. The LspB protein is involved in the secretion of the LspA1 and LspA2 proteins by Haemophilus ducreyi. Infect Immun 2004; 72:1874-84. [PMID: 15039306 PMCID: PMC375143 DOI: 10.1128/iai.72.4.1874-1884.2004] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The LspA1 and LspA2 proteins of Haemophilus ducreyi 35000 are two very large macromolecules that can be detected in concentrated culture supernatant fluid. Both of these proteins exhibit homology with the N-terminal region of the Bordetella pertussis filamentous hemagglutinin (FHA), which is involved in secretion of the latter macromolecule. The lspA2 open reading frame is flanked upstream by a gene, lspB, that encodes a predicted protein with homology to the B. pertussis FhaC outer membrane protein that is involved in secretion of FHA across the outer membrane. The H. ducreyi lspB gene encodes a protein with a predicted molecular mass of 66,573 Da. Reverse transcription-PCR analysis suggested that the lspB gene was transcribed together with the lspA2 gene on a single mRNA transcript. Polyclonal H. ducreyi LspB antiserum reacted with a 64-kDa antigen present in the Sarkosyl-insoluble cell envelope fraction of H. ducreyi 35000, which indicated that the LspB protein is likely an outer membrane protein. Concentrated culture supernatant fluids from H. ducreyi lspB and lspA1 lspB mutants did not contain detectable LspA1 and detectable LspA2, respectively. However, complementation of the lspB mutant with the wild-type lspB gene on a plasmid restored LspB protein expression and resulted in release of detectable amounts of the LspA1 protein into culture supernatant fluid. When evaluated in the temperature-dependent rabbit model of infection, the lspB mutant was attenuated in the ability to cause lesions and was never recovered in a viable form from lesions. These results indicated that the H. ducreyi LspB protein is involved in secretion of the LspA1 and LspA2 proteins across the outer membrane.
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Affiliation(s)
- Christine K Ward
- Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9048, USA
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45
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Clantin B, Hodak H, Willery E, Locht C, Jacob-Dubuisson F, Villeret V. The crystal structure of filamentous hemagglutinin secretion domain and its implications for the two-partner secretion pathway. Proc Natl Acad Sci U S A 2004; 101:6194-9. [PMID: 15079085 PMCID: PMC395945 DOI: 10.1073/pnas.0400291101] [Citation(s) in RCA: 137] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2004] [Accepted: 03/03/2004] [Indexed: 11/18/2022] Open
Abstract
Filamentous hemagglutinin (FHA), the major 230-kDa adhesin of the whooping cough agent Bordetella pertussis, is one of the most efficiently secreted proteins in Gram-negative bacteria. FHA is secreted by means of the two-partner secretion (TPS) pathway. Several important human, animal, and plant pathogens also secrete adhesins and other virulence factors by using this mode of secretion. A TPS system is composed of two separate proteins, with TpsA the secreted protein and TpsB its associated specific outermembrane transporter. All TPS-secreted proteins contain a distinctive N-proximal module essential for secretion, the TPS domain. We report here the 1.7- A structure of a functionally secreted 30-kDa N-terminal fragment of FHA. It reveals that the TPS domain folds into a beta-helix, with three extrahelical motifs, a beta-hairpin, a four-stranded beta-sheet, and an N-terminal capping, mostly formed by the nonconserved regions of the TPS domain. The structure thus explains why the TPS domain is able to initiate folding of the beta-helical motifs that form the central domain of the adhesin, because it is itself a beta-helical scaffold. It also contains less conserved extrahelical regions most likely involved in specific properties, such as the recognition of the outer-membrane transporter. This structure is representative of the TPS domains found so far in >100 secreted proteins from pathogenic bacteria. It also provides a mechanistic insight into how protein folding may be linked to secretion in the TPS pathway.
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Affiliation(s)
- Bernard Clantin
- Institut Fédératif de Recherche du Centre National de la Recherche Scientifique 3, Lille Cedex, France
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46
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Abstract
We introduce a model of DNA sequence evolution which can account for biases in mutation rates that depend on the identity of the neighboring bases. An analytic solution for this class of models is developed by adopting well-known methods of nonlinear dynamics. Results are presented for the CpG-methylation-deamination process, which dominates point substitutions in vertebrates. The dinucleotide frequencies generated by the model (using empirically obtained mutation rates) match the overall pattern observed in noncoding DNA. A web-based tool has been constructed to compute single- and dinucleotide frequencies for arbitrary neighbor-dependent mutation rates. Also provided is the backward procedure to infer the mutation rates using maximum likelihood analysis given the observed single- and dinucleotide frequencies. Reasonable estimates of the mutation rates can be obtained very efficiently, using generic noncoding DNA sequences as input, after masking out long homonucleotide subsequences. Our method is much more convenient and versatile to use than the traditional method of deducing mutation rates by counting mutation events in carefully chosen sequences. More generally, our approach provides a more realistic but still tractable description of noncoding genomic DNA and may be used as a null model for various sequence analysis applications.
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Affiliation(s)
- Peter F Arndt
- Department of Physics, University of California at San Diego, La Jolla, CA 92093, USA.
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Yen MR, Peabody CR, Partovi SM, Zhai Y, Tseng YH, Saier MH. Protein-translocating outer membrane porins of Gram-negative bacteria. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1562:6-31. [PMID: 11988218 DOI: 10.1016/s0005-2736(02)00359-0] [Citation(s) in RCA: 150] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Five families of outer membrane porins that function in protein secretion in Gram-negative bacteria are currently recognized. In this report, these five porin families are analyzed from structural and phylogenetic standpoints. They are the fimbrial usher protein (FUP), outer membrane factor (OMF), autotransporter (AT), two-partner secretion (TPS) and outer membrane secretin (Secretin) families. All members of these families in the current databases were identified, and all full-length homologues were multiply aligned for structural and phylogenetic analyses. The organismal distribution of homologues in each family proved to be unique with some families being restricted to proteobacteria and others being widespread in other bacterial kingdoms as well as eukaryotes. The compositions of and size differences between subfamilies provide evidence for specific orthologous relationships, which agree with available functional information and intra-subfamily phylogeny. The results reveal that horizontal transfer of genes encoding these proteins between phylogenetically distant organisms has been exceptionally rare although transfer within select bacterial kingdoms may have occurred. The resultant in silico analyses are correlated with available experimental evidence to formulate models relevant to the structures and evolutionary origins of these proteins.
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Affiliation(s)
- Ming Ren Yen
- Division of Biology 0116, 9500 Gilman Drive, University of California at San Diego, La Jolla, CA 92093-0116, USA
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Nelson KM, Young GM, Miller VL. Identification of a locus involved in systemic dissemination of Yersinia enterocolitica. Infect Immun 2001; 69:6201-8. [PMID: 11553561 PMCID: PMC98752 DOI: 10.1128/iai.69.10.6201-6208.2001] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2001] [Accepted: 06/18/2001] [Indexed: 11/20/2022] Open
Abstract
A putative LysR-type transcriptional activator, Hre20, was identified previously in an in vivo expression technology screen designed to identify factors which are expressed early during infection by Yersinia enterocolitica (G. M. Young and V. L. Miller, Mol. Microbiol. 25:319-328, 1997). An insertion in hre20, now designated rscR, resulted in increased splenic dissemination of bacteria during infection in a BALB/c mouse model. A nonpolar mutation was generated in rscR, and examination of this strain in the BALB/c mouse model demonstrated that the mutation in rscR was responsible for the increased dissemination to the spleen that was seen in the original experiments. RscR is homologous to the LysR family of transcriptional regulators; thus, a screen was undertaken to identify genes regulated by RscR. A strain containing an insertion in the chromosomal rscR gene and carrying rscR on a plasmid under the control of the inducible araBAD promoter was mutagenized with an mTn5Km-2 transposon containing a promoterless lacZY. Eighteen insertions were identified which appeared to respond to levels of RscR, and these were classified into four allelic groups based on Southern blot hybridization analysis. Representative members were sequenced from three allelic groups. Sequencing revealed insertions in an ORF with no known homologues, a homologue of OmpF of Serratia marcescens, and a locus (designated rscBAC) with similarity to the hmwABC locus of Haemophilus influenzae. The hmwABC locus promotes adherence of H. influenzae to host cells (S. J. Barenkamp and J. W. St. Geme III, Infect. Immun. 62:3320-3328, 1994; J. W. St. Geme III, S. Falkow, and S. J. Barenkamp, Proc. Natl. Acad. Sci. USA 90:2875-2879, 1993). A strain containing a deletion mutant of rscA, the hmwA homologue, exhibits increased splenic dissemination of bacteria during infection in a BALB/c mouse model, similar to the rscR mutant. This suggests that the phenotype of an rscR mutant is due to the loss of RscA.
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Affiliation(s)
- K M Nelson
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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Coutte L, Antoine R, Drobecq H, Locht C, Jacob-Dubuisson F. Subtilisin-like autotransporter serves as maturation protease in a bacterial secretion pathway. EMBO J 2001; 20:5040-8. [PMID: 11566869 PMCID: PMC125627 DOI: 10.1093/emboj/20.18.5040] [Citation(s) in RCA: 107] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Proteins of Gram-negative bacteria destined to the extracellular milieu must cross the two cellular membranes and then fold at the appropriate time and place. The synthesis of a precursor may be a strategy to maintain secretion competence while preventing aggregation or premature folding (especially for large proteins). The secretion of 230 kDa filamentous haemagglutinin (FHA) of Bordetella pertussis requires the synthesis and the maturation of a 367 kDa precursor that undergoes the proteolytic removal of its approximately 130 kDa C-terminal intramolecular chaperone domain. We have identified a specific protease, SphB1, responsible for the timely maturation of the precursor FhaB, which allows for extracellular release of FHA. SphB1 is a large exported protein with a subtilisin-like domain and a C-terminal domain typical of bacterial autotransporters. SphB1 is the first described subtilisin-like protein that serves as a specialized maturation protease in a secretion pathway of Gram-negative bacteria. This is reminiscent of pro-protein convertases of eukaryotic cells.
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Affiliation(s)
| | | | - Hervé Drobecq
- INSERM U447 and
CNRS UMR 8525, IBL, Institut Pasteur de Lille, 1 rue Calmette, 59019 Lille Cedex, France Corresponding author e-mail:
| | | | - Françoise Jacob-Dubuisson
- INSERM U447 and
CNRS UMR 8525, IBL, Institut Pasteur de Lille, 1 rue Calmette, 59019 Lille Cedex, France Corresponding author e-mail:
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Jacob-Dubuisson F, Locht C, Antoine R. Two-partner secretion in Gram-negative bacteria: a thrifty, specific pathway for large virulence proteins. Mol Microbiol 2001; 40:306-13. [PMID: 11309114 DOI: 10.1046/j.1365-2958.2001.02278.x] [Citation(s) in RCA: 213] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
A collection of large virulence exoproteins, including Ca2+-independent cytolysins, an iron acquisition protein and several adhesins, are secreted by the two-partner secretion (TPS) pathway in various Gram-negative bacteria. The hallmarks of the TPS pathway are the presence of an N-proximal module called the 'secretion domain' in the exoproteins that we have named the TpsA family, and the channel-forming beta-barrel transporter proteins we refer to as the TpsB family. The genes for cognate exoprotein and transporter protein are usually organized in an operon. Specific secretion signals are present in a highly conserved region of the secretion domain of TpsAs. TpsBs probably serve as specific receptors of the TpsA secretion signals and as channels for the translocation of the exoproteins across the outer membrane. A subfamily of transporters also mediates activation of their cognate cytolysins upon secretion. The exoproteins are synthesized as precursors with an N-terminal cleavable signal peptide, and a subset of them carries an extended signal peptide of unknown function. According to our current model, the exoproteins are probably translocated across the cytoplasmic membrane in a Sec-dependent fashion, and their signal peptide is probably processed by a LepB-type signal peptidase. The N-proximal secretion domain directs the exoproteins towards their transporters early, so that translocation across both membranes is coupled. The exoproteins transit through the periplasm in an extended conformation and fold progressively at the cell surface before eventually being released into the extracellular milieu. Several adhesins also undergo extensive proteolytic processing upon secretion. The genes of many new TpsAs and TpsBs are found in recently sequenced genomes, suggesting that the TPS pathway is widespread.
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Affiliation(s)
- F Jacob-Dubuisson
- INSERM U447, IBL, Institut Pasteur de Lille, 1 rue Calmette, 59019 Lille Cedex, France.
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