1
|
Barbat B, Douzi B, Voulhoux R. Structural lessons on bacterial secretins. Biochimie 2023; 205:110-116. [PMID: 36096236 DOI: 10.1016/j.biochi.2022.08.019] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2022] [Revised: 07/26/2022] [Accepted: 08/31/2022] [Indexed: 11/30/2022]
Abstract
To exchange and communicate with their surroundings, bacteria have evolved multiple active and passive mechanisms for trans-envelope transport. Among the pore-forming complexes found in the outer membrane of Gram-negative bacteria, secretins are distinctive homo-oligomeric channels dedicated to the active translocation of voluminous structures such as folded proteins, assembled fibers, virus particles or DNA. Members of the bacterial secretin family share a common cylinder-shaped structure with a gated pore-forming part inserted in the outer membrane, and a periplasmic channel connected to the inner membrane components of the corresponding nanomachine. In this mini-review, we will present what recently determined 3D structures have told us about the mechanisms of translocation through secretins of large substrates to the bacterial surface or in the extracellular milieu.
Collapse
Affiliation(s)
- Brice Barbat
- LCB-UMR7283, CNRS, Aix Marseille Université, IMM, 13009, Marseille, France
| | | | - Romé Voulhoux
- LCB-UMR7283, CNRS, Aix Marseille Université, IMM, 13009, Marseille, France.
| |
Collapse
|
2
|
Gurung JM, Amer AAA, Chen S, Diepold A, Francis MS. Type III secretion by Yersinia pseudotuberculosis is reliant upon an authentic N-terminal YscX secretor domain. Mol Microbiol 2022; 117:886-906. [PMID: 35043994 PMCID: PMC9303273 DOI: 10.1111/mmi.14880] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2021] [Revised: 01/04/2022] [Accepted: 01/11/2022] [Indexed: 11/29/2022]
Abstract
YscX was discovered as an essential part of the Yersinia type III secretion system about 20 years ago. It is required for substrate secretion and is exported itself. Despite this central role, its precise function and mode of action remains unknown. In order to address this knowledge gap, this present study refocused attention on YscX to build on the recent advances in the understanding of YscX function. Our experiments identified a N-terminal secretion domain in YscX promoting its secretion, with the first five codons constituting a minimal signal capable of promoting secretion of the signalless β-lactamase reporter. Replacing the extreme YscX N-terminus with known secretion signals of other Ysc-Yop substrates revealed that the YscX N-terminal segment contains non-redundant information needed for YscX function. Further, both in cis deletion of the YscX N-terminus in the virulence plasmid and ectopic expression of epitope tagged YscX variants again lead to stable YscX production but not type III secretion of Yop effector proteins. Mislocalisation of the needle components, SctI and SctF, accompanied this general defect in Yops secretion. Hence, a coupling exists between YscX secretion permissiveness and the assembly of an operational secretion system.
Collapse
Affiliation(s)
- Jyoti M Gurung
- Department of Molecular Biology, Umeå University, Umeå, Sweden.,Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, Sweden
| | - Ayad A A Amer
- Department of Molecular Biology, Umeå University, Umeå, Sweden.,Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, Sweden
| | - Shiyun Chen
- Wuhan Institute of Virology, The Chinese Academy of Sciences, Wuhan, China
| | - Andreas Diepold
- Max Planck Institute for Terrestrial Microbiology, Department of Ecophysiology, Marburg, Germany
| | - Matthew S Francis
- Department of Molecular Biology, Umeå University, Umeå, Sweden.,Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, Sweden
| |
Collapse
|
3
|
Hotinger JA, Pendergrass HA, May AE. Molecular Targets and Strategies for Inhibition of the Bacterial Type III Secretion System (T3SS); Inhibitors Directly Binding to T3SS Components. Biomolecules 2021; 11:biom11020316. [PMID: 33669653 PMCID: PMC7922566 DOI: 10.3390/biom11020316] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Revised: 02/16/2021] [Accepted: 02/17/2021] [Indexed: 01/01/2023] Open
Abstract
The type III secretion system (T3SS) is a virulence apparatus used by many Gram-negative pathogenic bacteria to cause infections. Pathogens utilizing a T3SS are responsible for millions of infections yearly. Since many T3SS knockout strains are incapable of causing systemic infection, the T3SS has emerged as an attractive anti-virulence target for therapeutic design. The T3SS is a multiprotein molecular syringe that enables pathogens to inject effector proteins into host cells. These effectors modify host cell mechanisms in a variety of ways beneficial to the pathogen. Due to the T3SS’s complex nature, there are numerous ways in which it can be targeted. This review will be focused on the direct targeting of components of the T3SS, including the needle, translocon, basal body, sorting platform, and effector proteins. Inhibitors will be considered a direct inhibitor if they have a binding partner that is a T3SS component, regardless of the inhibitory effect being structural or functional.
Collapse
|
4
|
Miletic S, Goessweiner-Mohr N, Marlovits TC. The Structure of the Type III Secretion System Needle Complex. Curr Top Microbiol Immunol 2020; 427:67-90. [PMID: 31667599 DOI: 10.1007/82_2019_178] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The type III secretion system (T3SS) is an essential virulence factor of many pathogenic bacterial species including Salmonella, Yersinia, Shigella and enteropathogenic Escherichia coli (EPEC). It is an intricate molecular machine that spans the bacterial membranes and injects effector proteins into target host cells, enabling bacterial infection. The T3SS needle complex comprises of proteinaceous rings supporting a needle filament which extends out into the extracellular environment. It serves as the central conduit for translocating effector proteins. Multiple laboratories have dedicated a remarkable effort to decipher the structure and function of the needle complex. A combination of structural biology techniques such as cryo-electron microscopy (cryoEM), X-ray crystallography, nuclear magnetic resonance (NMR) spectroscopy and computer modelling have been utilized to study different structural components at progressively higher resolutions. This chapter will provide an overview of the structural details of the T3SS needle complex, shedding light on this essential component of this fascinating bacterial system.
Collapse
Affiliation(s)
- Sean Miletic
- Center for Structural Systems Biology, Institute for Structural and Systems Biology, Universitätsklinikum Hamburg-Eppendorf, 85 Notkestraße, Hamburg, 22607, Germany
| | | | - Thomas C Marlovits
- Center for Structural Systems Biology, Institute for Structural and Systems Biology, Universitätsklinikum Hamburg-Eppendorf, 85 Notkestraße, Hamburg, 22607, Germany.
| |
Collapse
|
5
|
Hu J, Worrall LJ, Hong C, Vuckovic M, Atkinson CE, Caveney N, Yu Z, Strynadka NCJ. Cryo-EM analysis of the T3S injectisome reveals the structure of the needle and open secretin. Nat Commun 2018; 9:3840. [PMID: 30242280 PMCID: PMC6155069 DOI: 10.1038/s41467-018-06298-8] [Citation(s) in RCA: 73] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2018] [Accepted: 07/20/2018] [Indexed: 11/09/2022] Open
Abstract
The bacterial type III secretion system, or injectisome, is a syringe shaped nanomachine essential for the virulence of many disease causing Gram-negative bacteria. At the core of the injectisome structure is the needle complex, a continuous channel formed by the highly oligomerized inner and outer membrane hollow rings and a polymerized helical needle filament which spans through and projects into the infected host cell. Here we present the near-atomic resolution structure of a needle complex from the prototypical Salmonella Typhimurium SPI-1 type III secretion system, with local masking protocols allowing for model building and refinement of the major membrane spanning components of the needle complex base in addition to an isolated needle filament. This work provides significant insight into injectisome structure and assembly and importantly captures the molecular basis for substrate induced gating in the giant outer membrane secretin portal family.
Collapse
Affiliation(s)
- J Hu
- Department of Biochemistry and Molecular Biology and the Centre for Blood Research, University of British Columbia, Vancouver, V6T 1Z3, BC, Canada
| | - L J Worrall
- Department of Biochemistry and Molecular Biology and the Centre for Blood Research, University of British Columbia, Vancouver, V6T 1Z3, BC, Canada
- HRMEM facility, University of British Columbia, Vancouver, V6T 1Z3, BC, Canada
| | - C Hong
- CryoEM Shared Resources, Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, 20147, VA, USA
| | - M Vuckovic
- Department of Biochemistry and Molecular Biology and the Centre for Blood Research, University of British Columbia, Vancouver, V6T 1Z3, BC, Canada
| | - C E Atkinson
- Department of Biochemistry and Molecular Biology and the Centre for Blood Research, University of British Columbia, Vancouver, V6T 1Z3, BC, Canada
- HRMEM facility, University of British Columbia, Vancouver, V6T 1Z3, BC, Canada
| | - N Caveney
- Department of Biochemistry and Molecular Biology and the Centre for Blood Research, University of British Columbia, Vancouver, V6T 1Z3, BC, Canada
| | - Z Yu
- CryoEM Shared Resources, Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, 20147, VA, USA
| | - N C J Strynadka
- Department of Biochemistry and Molecular Biology and the Centre for Blood Research, University of British Columbia, Vancouver, V6T 1Z3, BC, Canada.
| |
Collapse
|
6
|
Kooger R, Szwedziak P, Böck D, Pilhofer M. CryoEM of bacterial secretion systems. Curr Opin Struct Biol 2018; 52:64-70. [PMID: 30223223 DOI: 10.1016/j.sbi.2018.08.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Revised: 05/18/2018] [Accepted: 08/29/2018] [Indexed: 02/06/2023]
Abstract
The need for bacteria to interact with their environment has driven the evolution of elaborate secretion systems. By virtue of their function, secretion systems are macromolecular complexes associated with the cell envelope and therefore inherently difficult to study by conventional structural biology techniques. Cryo-electron microscopy (cryoEM) has become an invaluable technique to study large membrane-embedded complexes and led to major advances in the mechanistic understanding of secretion systems. CryoEM comprises of two main modalities, namely single particle analysis and tomography. Here, we review how detailed structures retrieved by single particle analysis combine elegantly with tomography experiments in which the secretion systems are observed in their native cellular context.
Collapse
Affiliation(s)
- Romain Kooger
- Institute of Molecular Biology & Biophysics, Eidgenössische Technische Hochschule Zürich, CH-8093 Zürich, Switzerland
| | - Piotr Szwedziak
- Institute of Molecular Biology & Biophysics, Eidgenössische Technische Hochschule Zürich, CH-8093 Zürich, Switzerland
| | - Désirée Böck
- Institute of Molecular Biology & Biophysics, Eidgenössische Technische Hochschule Zürich, CH-8093 Zürich, Switzerland
| | - Martin Pilhofer
- Institute of Molecular Biology & Biophysics, Eidgenössische Technische Hochschule Zürich, CH-8093 Zürich, Switzerland.
| |
Collapse
|
7
|
Majewski DD, Worrall LJ, Strynadka NCJ. Secretins revealed: structural insights into the giant gated outer membrane portals of bacteria. Curr Opin Struct Biol 2018; 51:61-72. [DOI: 10.1016/j.sbi.2018.02.008] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2017] [Accepted: 02/28/2018] [Indexed: 01/19/2023]
|
8
|
Rapisarda C, Tassinari M, Gubellini F, Fronzes R. Using Cryo-EM to Investigate Bacterial Secretion Systems. Annu Rev Microbiol 2018; 72:231-254. [PMID: 30004822 DOI: 10.1146/annurev-micro-090817-062702] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Bacterial secretion systems are responsible for releasing macromolecules to the extracellular milieu or directly into other cells. These membrane complexes are associated with pathogenicity and bacterial fitness. Understanding of these large assemblies has exponentially increased in the last few years thanks to electron microscopy. In fact, a revolution in this field has led to breakthroughs in characterizing the structures of secretion systems and other macromolecular machineries so as to obtain high-resolution images of complexes that could not be crystallized. In this review, we give a brief overview of structural advancements in the understanding of secretion systems, focusing in particular on cryo-electron microscopy, whether tomography or single-particle analysis. We describe how such techniques have contributed to knowledge of the mechanism of macromolecule secretion in bacteria and the impact they will have in the future.
Collapse
Affiliation(s)
- Chiara Rapisarda
- Structure et Fonction des Nanomachines Bactériennes, Institut Européen de Chimie et Biologie, 33607 Pessac, France; , .,CNRS UMR5234, Université de Bordeaux, 33076 Bordeaux, France
| | - Matteo Tassinari
- Institut Pasteur, Unité de Microbiologie Structurale, 75724 Paris, France; .,CNRS UMR3528, Institut Pasteur, 75015 Paris, France
| | - Francesca Gubellini
- Institut Pasteur, Unité de Microbiologie Structurale, 75724 Paris, France; .,CNRS UMR3528, Institut Pasteur, 75015 Paris, France
| | - Rémi Fronzes
- Structure et Fonction des Nanomachines Bactériennes, Institut Européen de Chimie et Biologie, 33607 Pessac, France; , .,CNRS UMR5234, Université de Bordeaux, 33076 Bordeaux, France
| |
Collapse
|
9
|
The role of EscD in supporting EscC polymerization in the type III secretion system of enteropathogenic Escherichia coli. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1860:384-395. [PMID: 28988128 DOI: 10.1016/j.bbamem.2017.10.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2017] [Revised: 10/01/2017] [Accepted: 10/02/2017] [Indexed: 11/23/2022]
Abstract
The type III secretion system (T3SS) is a multi-protein complex that plays a central role in the virulence of many Gram-negative bacterial pathogens. In enteropathogenic Escherichia coli, a prevalent cause of diarrheal diseases, the needle complex base of the T3SS is formed by multi-rings: two concentric inner-membrane rings made by the two oligomerizing proteins (EscD and EscJ), and an outer ring made of a single oligomerizing protein (EscC). Although the oligomerization activity of these proteins is critical for their function and can, therefore, affect the virulence of the pathogen, the mechanisms underlying the oligomerization of these proteins have yet to be identified. In this study, we report that the proteins forming the inner-membrane T3SS rings, EscJ and EscD proteins, are crucial for the oligomerization of EscC. Moreover, we elucidate the oligomerization process of EscD and determine the contribution of individual regions of the protein to its self-oligomerization activity. We show that the oligomerization motif of EscD is located at its N-terminal portion and that its transmembrane domain can self-oligomerize, thus contributing to the self-oligomerization of the full-length EscD.
Collapse
|
10
|
Cao SY, Liu WB, Tan YF, Yang HY, Zhang TT, Wang T, Wang XY, Song YJ, Yang RF, Du ZM. An Interaction between the Inner Rod Protein YscI and the Needle Protein YscF Is Required to Assemble the Needle Structure of the Yersinia Type Three Secretion System. J Biol Chem 2017; 292:5488-5498. [PMID: 28196868 DOI: 10.1074/jbc.m116.743591] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Revised: 02/09/2017] [Indexed: 11/06/2022] Open
Abstract
The type III secretion system is a highly conserved virulence mechanism that is widely distributed in Gram-negative bacteria. It has a syringe-like structure composed of a multi-ring basal body that spans the bacterial envelope and a projecting needle that delivers virulence effectors into host cells. Here, we showed that the Yersinia inner rod protein YscI directly interacts with the needle protein YscF inside the bacterial cells and that this interaction depends on amino acid residues 83-102 in the carboxyl terminus of YscI. Alanine substitution of Trp-85 or Ser-86 abrogated the binding of YscI to YscF as well as needle assembly and the secretion of effectors (Yops) and the needle tip protein LcrV. However, yscI null mutants that were trans-complemented with YscI mutants that bind YscF still assembled the needle and secreted Yops, demonstrating that a direct interaction between YscF and YscI is critical for these processes. Consistently, YscI mutants that did not bind YscF resulted in greatly decreased HeLa cell cytotoxicity. Together, these results show that YscI participates in needle assembly by directly interacting with YscF.
Collapse
Affiliation(s)
- Shi-Yang Cao
- From the State Key laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, China
| | - Wan-Bin Liu
- From the State Key laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, China
| | - Ya-Fang Tan
- From the State Key laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, China
| | - Hui-Ying Yang
- From the State Key laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, China
| | - Ting-Ting Zhang
- From the State Key laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, China
| | - Tong Wang
- From the State Key laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, China
| | - Xiao-Yi Wang
- From the State Key laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, China
| | - Ya-Jun Song
- From the State Key laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, China
| | - Rui-Fu Yang
- From the State Key laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, China
| | - Zong-Min Du
- From the State Key laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, China
| |
Collapse
|
11
|
Worrall LJ, Hong C, Vuckovic M, Deng W, Bergeron JRC, Majewski DD, Huang RK, Spreter T, Finlay BB, Yu Z, Strynadka NCJ. Near-atomic-resolution cryo-EM analysis of the Salmonella T3S injectisome basal body. Nature 2016; 540:597-601. [DOI: 10.1038/nature20576] [Citation(s) in RCA: 109] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Accepted: 10/25/2016] [Indexed: 12/17/2022]
|
12
|
Abstract
UNLABELLED Type IV pili (T4Ps) are surface appendages used by Gram-negative and Gram-positive pathogens for motility and attachment to epithelial surfaces. In Gram-negative bacteria, such as the important pediatric pathogen enteropathogenic Escherichia coli (EPEC), during extension and retraction, the pilus passes through an outer membrane (OM) pore formed by the multimeric secretin complex. The secretin is common to Gram-negative assemblies, including the related type 2 secretion (T2S) system and the type 3 secretion (T3S) system. The N termini of the secretin monomers are periplasmic and in some systems have been shown to mediate substrate specificity. In this study, we mapped the topology of BfpB, the T4P secretin from EPEC, using a combination of biochemical and biophysical techniques that allowed selective identification of periplasmic and extracellular residues. We applied rules based on solved atomic structures of outer membrane proteins (OMPs) to generate our topology model, combining the experimental results with secondary structure prediction algorithms and direct inspection of the primary sequence. Surprisingly, the C terminus of BfpB is extracellular, a result confirmed by flow cytometry for BfpB and a distantly related T4P secretin, PilQ, from Pseudomonas aeruginosa. Keeping with prior evidence, the C termini of two T2S secretins and one T3S secretin were not detected on the extracellular surface. On the basis of our data and structural constraints, we propose that BfpB forms a beta barrel with 16 transmembrane beta strands. We propose that the T4P secretins have a C-terminal segment that passes through the center of each monomer. IMPORTANCE Secretins are multimeric proteins that allow the passage of secreted toxins and surface structures through the outer membranes (OMs) of Gram-negative bacteria. To date, there have been no atomic structures of the C-terminal region of a secretin, although electron microscopy (EM) structures of the complex are available. This work provides a detailed topology prediction of the membrane-spanning domain of a type IV pilus (T4P) secretin. Our study used innovative techniques to provide new and comprehensive information on secretin topology, highlighting similarities and differences among secretin subfamilies. Additionally, the techniques used in this study may prove useful for the study of other OM proteins.
Collapse
|
13
|
ExsB is required for correct assembly of the Pseudomonas aeruginosa type III secretion apparatus in the bacterial membrane and full virulence in vivo. Infect Immun 2015; 83:1789-98. [PMID: 25690097 DOI: 10.1128/iai.00048-15] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2015] [Accepted: 02/06/2015] [Indexed: 01/31/2023] Open
Abstract
Pseudomonas aeruginosa is responsible for high-morbidity infections of cystic fibrosis patients and is a major agent of nosocomial infections. One of its most potent virulence factors is a type III secretion system (T3SS) that injects toxins directly into the host cell cytoplasm. ExsB, a lipoprotein localized in the bacterial outer membrane, is one of the components of this machinery, of which the function remained elusive until now. The localization of the exsB gene within the exsCEBA regulatory gene operon suggested an implication in the T3SS regulation, while its similarity with yscW from Yersinia spp. argued in favor of a role in machinery assembly. The present work shows that ExsB is necessary for full in vivo virulence of P. aeruginosa. Furthermore, the requirement of ExsB for optimal T3SS assembly and activity is demonstrated using eukaryotic cell infection and in vitro assays. In particular, ExsB promotes the assembly of the T3SS secretin in the bacterial outer membrane, highlighting the molecular role of ExsB as a pilotin. This involvement in the regulation of the T3S apparatus assembly may explain the localization of the ExsB-encoding gene within the regulatory gene operon.
Collapse
|
14
|
Kudryashev M, Diepold A, Amstutz M, Armitage JP, Stahlberg H, Cornelis GR. Y
ersinia enterocolitica
type
III
secretion injectisomes form regularly spaced clusters, which incorporate new machines upon activation. Mol Microbiol 2015; 95:875-84. [DOI: 10.1111/mmi.12908] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/12/2014] [Indexed: 11/29/2022]
Affiliation(s)
- Mikhail Kudryashev
- Center for Cellular Imaging and NanoAnalytics (C‐CINA) Biozentrum, University Basel WRO‐1058, Mattenstrasse 26 Basel 4058 Switzerland
- Focal Area Infection Biology Biozentrum, University of Basel Klingelbergstrasse 50/70 Basel 4056 Switzerland
| | - Andreas Diepold
- Department of Biochemistry University of Oxford South Parks Road Oxford OX1 3QU UK
| | - Marlise Amstutz
- Focal Area Infection Biology Biozentrum, University of Basel Klingelbergstrasse 50/70 Basel 4056 Switzerland
| | - Judith P. Armitage
- Department of Biochemistry University of Oxford South Parks Road Oxford OX1 3QU UK
| | - Henning Stahlberg
- Center for Cellular Imaging and NanoAnalytics (C‐CINA) Biozentrum, University Basel WRO‐1058, Mattenstrasse 26 Basel 4058 Switzerland
| | - Guy R. Cornelis
- Focal Area Infection Biology Biozentrum, University of Basel Klingelbergstrasse 50/70 Basel 4056 Switzerland
- Research Unit in Microorganism Biology University of Namur 61 rue de Bruxelles 5000 Namur Belgium
| |
Collapse
|
15
|
Diffusion of antibiotics through the PilQ secretin in Neisseria gonorrhoeae occurs through the immature, sodium dodecyl sulfate-labile form. J Bacteriol 2015; 197:1308-21. [PMID: 25605303 DOI: 10.1128/jb.02628-14] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
UNLABELLED In strains of Neisseria gonorrhoeae harboring the mtr and penB determinants that decrease permeation of antibiotics into the periplasm, mutation or deletion of the PilQ secretin of type IV pili increases resistance to penicillin by ∼3-fold, indicating a role for PilQ in antibiotic permeation. In this study, we examined spontaneously arising mutants with decreased susceptibility to penicillin. One class of mutants had a phenotype indistinguishable from that of a previously characterized pilQ2 mutation that interfered with the formation of SDS-resistant PilQ multimers. A second class of mutants contained frameshift mutations in genes upstream of pilQ in the pilMNOPQ operon that increased resistance to levels similar to those of the pilQ2 mutation. In-frame deletions of these genes were constructed, but only the frameshift mutations increased antibiotic resistance, suggesting that the mutations had polar effects on PilQ. Consistent with this result, titration of wild-type PilQ levels revealed a direct correlation between resistance and expression levels of PilQ. To determine which form of PilQ, the monomer or the multimer, was responsible for antibiotic permeation, we manipulated and quantified these forms in different mutants. Deletion of PilW, which is responsible for the maturation of PilQ into SDS-resistant multimers, had no effect on resistance. Moreover, Western blot analysis revealed that while SDS-resistant multimer levels were decreased by 26% in frameshift mutants, the levels of PilQ monomers were decreased by 48%. These data suggest that immature, SDS-labile complexes, not mature, SDS-resistant PilQ complexes, serve as the route of entry of antibiotics into the periplasm. IMPORTANCE The capacity of antibiotics to reach their target is crucial for their activity. In Neisseria gonorrhoeae, the PilQ secretin of type IV pili plays an important role in antibiotic influx when diffusion of antibiotics through porins is limited (e.g., in most resistant strains). On Western blots, PilQ exists both as a mature higher-order multimer and an immature, SDS-labile monomer. In this study, we examined spontaneously arising mutations in PilQ and in the genes upstream of PilQ in the pilMNOPQ operon that increase resistance to penicillin. We provide evidence that PilQ monomers associate by mass action to form immature multimers and that these complexes likely mediate the diffusion of antibiotics across the outer membrane.
Collapse
|
16
|
Abstract
Secretins are major constituents of bacterial type III secretion systems (T3SS). In this issue of Structure, Kowal and colleagues report on the cryo-EM structure of the native YscC secretin from Yersinia, revealing its internal symmetry and mode of length adaptation.
Collapse
Affiliation(s)
- Dirk W Heinz
- Helmholtz Centre for Infection Research, Inhoffenstraße 7, D-38124 Braunschweig, Germany.
| |
Collapse
|
17
|
Tosi T, Estrozi L, Job V, Guilvout I, Pugsley A, Schoehn G, Dessen A. Structural Similarity of Secretins from Type II and Type III Secretion Systems. Structure 2014; 22:1348-1355. [DOI: 10.1016/j.str.2014.07.005] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2013] [Revised: 06/02/2014] [Accepted: 07/21/2014] [Indexed: 01/07/2023]
|
18
|
Abstract
Bacteria secrete and harbor in their membranes a number of pore-forming proteins. Some of these are bona fide ion channels that may respond to changes in membrane tension, voltage, or pH. Others may be large translocons used for the secretion of folded or unfolded polypeptide substrates. Additionally, many secreted toxins insert into target cell membranes and form pores that either collapse membrane electrochemical gradients or provide conduits for the delivery of virulence factors. In all cases, electrophysiological approaches have yielded much progress in past decades in understanding the functional mechanisms of these pores. By monitoring the changes in current due to ion flow through the pores, these techniques are used as high-resolution tools to gather detailed information on the kinetic and permeation properties of these proteins, including those whose physiological role is not ion flux. This review highlights some of the electrophysiological studies that have advanced the field of transport by pore-forming proteins of bacterial origin.
Collapse
Affiliation(s)
- Anne H Delcour
- Department of Biology and Biochemistry, University of Houston, Houston, Texas 77204-5001;
| |
Collapse
|
19
|
Diepold A, Wagner S. Assembly of the bacterial type III secretion machinery. FEMS Microbiol Rev 2014; 38:802-22. [PMID: 24484471 DOI: 10.1111/1574-6976.12061] [Citation(s) in RCA: 113] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2013] [Revised: 01/02/2014] [Accepted: 01/13/2014] [Indexed: 11/29/2022] Open
Abstract
Many bacteria that live in contact with eukaryotic hosts, whether as symbionts or as pathogens, have evolved mechanisms that manipulate host cell behaviour to their benefit. One such mechanism, the type III secretion system, is employed by Gram-negative bacterial species to inject effector proteins into host cells. This function is reflected by the overall shape of the machinery, which resembles a molecular syringe. Despite the simplicity of the concept, the type III secretion system is one of the most complex known bacterial nanomachines, incorporating one to more than hundred copies of up to twenty different proteins into a multi-MDa transmembrane complex. The structural core of the system is the so-called needle complex that spans the bacterial cell envelope as a tripartite ring system and culminates in a needle protruding from the bacterial cell surface. Substrate targeting and translocation are accomplished by an export machinery consisting of various inner membrane embedded and cytoplasmic components. The formation of such a multimembrane-spanning machinery is an intricate task that requires precise orchestration. This review gives an overview of recent findings on the assembly of type III secretion machines, discusses quality control and recycling of the system and proposes an integrated assembly model.
Collapse
Affiliation(s)
- Andreas Diepold
- Department of Biochemistry, University of Oxford, Oxford, UK
| | | |
Collapse
|
20
|
Kowal J, Chami M, Ringler P, Müller S, Kudryashev M, Castaño-Díez D, Amstutz M, Cornelis G, Stahlberg H, Engel A. Structure of the Dodecameric Yersinia enterocolitica Secretin YscC and Its Trypsin-Resistant Core. Structure 2013; 21:2152-61. [DOI: 10.1016/j.str.2013.09.012] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2013] [Revised: 09/04/2013] [Accepted: 09/11/2013] [Indexed: 10/26/2022]
|
21
|
Abstract
Proteins called secretins form large multimeric complexes that are essential for macromolecular transit across the outer membrane of Gram-negative bacteria. Evidence suggests that the channels formed by some secretin complexes are not tightly closed, but their permeability properties have not been well characterized. Here, we used cell-free synthesis coupled with spontaneous insertion into liposomes to investigate the permeability of the secretin PulD. Leakage assays using preloaded liposomes indicated that PulD allows the efflux of small fluorescent molecules with a permeation cutoff similar to that of general porins. Other secretins were also found to form similar pores. To define the polypeptide region involved in determining the pore size, we analyzed a collection of PulD variants and studied the roles of gates 1 and 2, which were previously reported to affect the pore size of filamentous phage f1 secretin pIV, in assembly and pore formation. Liposome leakage and a novel in vivo assay showed that replacement of the conserved proline residue at position 443 in PulD by leucine increased the apparent size of the pore. The in vitro approach described here could be used to study the pore properties of membrane proteins whose production in vivo is toxic.
Collapse
|
22
|
Abstract
Secretion of effectors across bacterial membranes is usually mediated by large multisubunit complexes. In most cases, the secreted effectors are virulent factors normally associated to pathogenic diseases. The biogenesis of these secretion systems and the transport of the effectors are processes that require energy. This energy could be directly obtained by using the proton motive force, but in most cases the energy associated to these processes is derived from ATP hydrolysis. Here, a description of the machineries involved in generating the energy required for system biogenesis and substrate transport by type II, III and IV secretion systems is provided, with special emphasis on highlighting the structural similarities and evolutionary relationships among the secretion ATPases.
Collapse
Affiliation(s)
- Alejandro Peña
- Departamento de Biología Molecular, Universidad de Cantabria, UC-CSIC-SODERCAN, Santander, Spain
| | | |
Collapse
|
23
|
Kudryashev M, Stenta M, Schmelz S, Amstutz M, Wiesand U, Castaño-Díez D, Degiacomi MT, Münnich S, Bleck CK, Kowal J, Diepold A, Heinz DW, Dal Peraro M, Cornelis GR, Stahlberg H. In situ structural analysis of the Yersinia enterocolitica injectisome. eLife 2013; 2:e00792. [PMID: 23908767 PMCID: PMC3728920 DOI: 10.7554/elife.00792] [Citation(s) in RCA: 82] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2013] [Accepted: 06/27/2013] [Indexed: 12/20/2022] Open
Abstract
Injectisomes are multi-protein transmembrane machines allowing pathogenic bacteria to
inject effector proteins into eukaryotic host cells, a process called type III
secretion. Here we present the first three-dimensional structure of Yersinia
enterocolitica and Shigella flexneri injectisomes in
situ and the first structural analysis of the Yersinia injectisome.
Unexpectedly, basal bodies of injectisomes inside the bacterial cells showed length
variations of 20%. The in situ structures of the Y. enterocolitica
and S. flexneri injectisomes had similar dimensions and were
significantly longer than the isolated structures of related injectisomes. The
crystal structure of the inner membrane injectisome component YscD appeared elongated
compared to a homologous protein, and molecular dynamics simulations documented its
elongation elasticity. The ring-shaped secretin YscC at the outer membrane was
stretched by 30–40% in situ, compared to its isolated liposome-embedded
conformation. We suggest that elasticity is critical for some two-membrane spanning
protein complexes to cope with variations in the intermembrane distance. DOI:http://dx.doi.org/10.7554/eLife.00792.001 Humans and other animals can use the five senses—touch, taste, sight, smell,
and hearing—to interpret the world around them. Single-celled organisms,
however, must rely on molecular cues to understand their immediate surroundings. In
particular, bacteria gather information about external conditions, including
potential hosts nearby, by secreting protein sensors that can relay messages back to
the cell. Bacteria export these sensors via secretion systems that enable the organism both to
receive information about the environment and to invade a host cell. A total of seven
separate secretion systems, known as types I–VII, have been identified. These
different secretion systems handle distinct cargoes, allowing the bacterial cell to
respond to a range of feedback from the external milieu. The type III secretion system, also known as the ‘injectisome’, is
found in bacterial species that are enclosed by two membranes separated by a
periplasmic space. The injectisome comprises different components that combine to
form the basal body, which spans the inner and outer membranes, and a projection from
the basal body, called the hollow needle, that mediates the export of cargo from a
bacterium to its host or the local environment. The distance between the inner and outer membranes may vary across species or
according to environmental conditions, so the basal body must be able to accommodate
these changes. However, no mechanism has yet been established that might introduce
such elasticity into the injectisome. Now, Kudryashev et al. have generated
three-dimensional structures for the injectisomes of two species of bacteria,
Shigella flexneri and Yersinia enterocolitica,
and shown that the size of the basal body can fluctuate by up to 20%. Kudryashev et al. imaged whole injectisomes in these two species and found that the
height of the basal body was proportional to the distance between the inner and outer
membranes. To probe how this could occur, the properties of two proteins that are
important components of the basal body were studied in greater detail. YscD, a
protein that extends across the periplasmic space, was crystallized and its structure
was then determined and used to develop a computer model to assess its
compressibility: this model indicated that YscD could stretch or contract by up to
50% of its total length. The outer membrane component YscC also appeared elastic:
when the protein was isolated and introduced into synthetic membranes, its length was
reduced 30–40% relative to that observed in intact bacterial membranes. A further experiment confirmed the adaptability of the basal body: when the
separation of the membranes was deliberately increased by placing bacteria in a
high-salt medium, the basal body extended approximately 10% in length. Cumulatively,
therefore, these experiments suggest that the in-built flexibility of the basal body
of the injectisome allows bacteria to adjust to environmental changes while
maintaining their sensory abilities and host-invasion potential. DOI:http://dx.doi.org/10.7554/eLife.00792.002
Collapse
Affiliation(s)
- Mikhail Kudryashev
- Center for Cellular Imaging and NanoAnalytics (C-CINA) , Biozentrum, University of Basel , Basel , Switzerland
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
24
|
Bergeron JRC, Worrall LJ, Sgourakis NG, DiMaio F, Pfuetzner RA, Felise HB, Vuckovic M, Yu AC, Miller SI, Baker D, Strynadka NCJ. A refined model of the prototypical Salmonella SPI-1 T3SS basal body reveals the molecular basis for its assembly. PLoS Pathog 2013; 9:e1003307. [PMID: 23633951 PMCID: PMC3635987 DOI: 10.1371/journal.ppat.1003307] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2012] [Accepted: 03/02/2013] [Indexed: 12/22/2022] Open
Abstract
The T3SS injectisome is a syringe-shaped macromolecular assembly found in pathogenic Gram-negative bacteria that allows for the direct delivery of virulence effectors into host cells. It is composed of a “basal body”, a lock-nut structure spanning both bacterial membranes, and a “needle” that protrudes away from the bacterial surface. A hollow channel spans throughout the apparatus, permitting the translocation of effector proteins from the bacterial cytosol to the host plasma membrane. The basal body is composed largely of three membrane-embedded proteins that form oligomerized concentric rings. Here, we report the crystal structures of three domains of the prototypical Salmonella SPI-1 basal body, and use a new approach incorporating symmetric flexible backbone docking and EM data to produce a model for their oligomeric assembly. The obtained models, validated by biochemical and in vivo assays, reveal the molecular details of the interactions driving basal body assembly, and notably demonstrate a conserved oligomerization mechanism. Gram-negative bacteria such as E. coli, Salmonella, Shigella, Pseudomonas aeruginosa, and Yersinia pestis are responsible for a wide range of diseases, from pneumonia to lethal diarrhea and plague. A common trait shared by these bacteria is their capacity to inject toxins directly inside the cells of infected individuals, thanks to a syringe-shaped “nano-machine” called the Type III Secretion System injectisome. These toxins lead to modifications of the host cell, allowing the bacteria to replicate efficiently and/or to evade the immune system, and are necessary to establish an infection. As a consequence, the injectisome is an important potential target for the development of novel therapeutics against bacterial infection. In this study, we focus on the basal body, an essential region of the injectisome that forms the continuous hollow channel across both membranes of the bacteria. We have used an array of biophysical methods to obtain an atomic model of the basal body. This model provides new insights as to how the basal body assembles at the surface of bacteria, and could be used for the design of novel antibiotics.
Collapse
Affiliation(s)
- Julien R. C. Bergeron
- Department of Biochemistry and Molecular Biology, and Centre for Blood Research, University of British Columbia, Vancouver, British Columbia, Canada
| | - Liam J. Worrall
- Department of Biochemistry and Molecular Biology, and Centre for Blood Research, University of British Columbia, Vancouver, British Columbia, Canada
| | - Nikolaos G. Sgourakis
- Department of Biochemistry, University of Washington, Seattle, Washington, United States of America
| | - Frank DiMaio
- Department of Biochemistry, University of Washington, Seattle, Washington, United States of America
| | - Richard A. Pfuetzner
- Department of Microbiology, University of Washington, Seattle, Washington, United States of America
| | - Heather B. Felise
- Department of Microbiology, University of Washington, Seattle, Washington, United States of America
| | - Marija Vuckovic
- Department of Biochemistry and Molecular Biology, and Centre for Blood Research, University of British Columbia, Vancouver, British Columbia, Canada
| | - Angel C. Yu
- Department of Biochemistry and Molecular Biology, and Centre for Blood Research, University of British Columbia, Vancouver, British Columbia, Canada
| | - Samuel I. Miller
- Department of Microbiology, University of Washington, Seattle, Washington, United States of America
- Department of Genome Sciences, University of Washington, Seattle, Washington, United States of America
- Department of Medicine, University of Washington, Seattle, Washington, United States of America
| | - David Baker
- Department of Biochemistry, University of Washington, Seattle, Washington, United States of America
- Department of Genome Sciences, University of Washington, Seattle, Washington, United States of America
- Howard Hughes Medical Institute, University of Washington, Seattle, Washington, United States of America
- * E-mail: (DB); (NCJS)
| | - Natalie C. J. Strynadka
- Department of Biochemistry and Molecular Biology, and Centre for Blood Research, University of British Columbia, Vancouver, British Columbia, Canada
- * E-mail: (DB); (NCJS)
| |
Collapse
|
25
|
Demarcating SurA activities required for outer membrane targeting of Yersinia pseudotuberculosis adhesins. Infect Immun 2013; 81:2296-308. [PMID: 23589578 DOI: 10.1128/iai.01208-12] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
SurA is a periplasmic protein folding factor involved in chaperoning and trafficking of outer membrane proteins across the Gram-negative bacterial periplasm. In addition, SurA also possesses peptidyl-prolyl cis/trans isomerase activity. We have previously reported that in enteropathogenic Yersinia pseudotuberculosis, SurA is needed for bacterial virulence and envelope integrity. In this study, we investigated the role of SurA in the assembly of important Yersinia adhesins. Using genetic mutation, biochemical characterization, and an in vitro-based bacterial host cell association assay, we confirmed that surface localization of the invasin adhesin is dependent on SurA. As a surA deletion also has some impact on the levels of individual components of the BAM complex in the Yersinia outer membrane, abolished invasin surface assembly could reflect both a direct loss of SurA-dependent periplasmic targeting and a potentially compromised BAM complex assembly platform in the outer membrane. To various degrees, the assembly of two other adhesins, Ail and the pH 6 antigen fibrillum PsaA, also depends on SurA. Consequently, loss of SurA leads to a dramatic reduction in Yersinia attachment to eukaryotic host cells. Genetic complementation of surA deletion mutants indicated a prominent role for SurA chaperone function in outer membrane protein assembly. Significantly, the N terminus of SurA contributed most of this SurA chaperone function. Despite a dominant chaperoning role, it was also evident that SurA isomerization activity did make a modest contribution to this assembly process.
Collapse
|
26
|
Chatterjee S, Chaudhury S, McShan AC, Kaur K, De Guzman RN. Structure and biophysics of type III secretion in bacteria. Biochemistry 2013; 52:2508-17. [PMID: 23521714 DOI: 10.1021/bi400160a] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Many plant and animal bacterial pathogens assemble a needle-like nanomachine, the type III secretion system (T3SS), to inject virulence proteins directly into eukaryotic cells to initiate infection. The ability of bacteria to inject effectors into host cells is essential for infection, survival, and pathogenesis for many Gram-negative bacteria, including Salmonella, Escherichia, Shigella, Yersinia, Pseudomonas, and Chlamydia spp. These pathogens are responsible for a wide variety of diseases, such as typhoid fever, large-scale food-borne illnesses, dysentery, bubonic plague, secondary hospital infections, and sexually transmitted diseases. The T3SS consists of structural and nonstructural proteins. The structural proteins assemble the needle apparatus, which consists of a membrane-embedded basal structure, an external needle that protrudes from the bacterial surface, and a tip complex that caps the needle. Upon host cell contact, a translocon is assembled between the needle tip complex and the host cell, serving as a gateway for translocation of effector proteins by creating a pore in the host cell membrane. Following delivery into the host cytoplasm, effectors initiate and maintain infection by manipulating host cell biology, such as cell signaling, secretory trafficking, cytoskeletal dynamics, and the inflammatory response. Finally, chaperones serve as regulators of secretion by sequestering effectors and some structural proteins within the bacterial cytoplasm. This review will focus on the latest developments and future challenges concerning the structure and biophysics of the needle apparatus.
Collapse
Affiliation(s)
- Srirupa Chatterjee
- Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas 66045, USA
| | | | | | | | | |
Collapse
|
27
|
Yang H, Tan Y, Zhang T, Tang L, Wang J, Ke Y, Guo Z, Yang X, Yang R, Du Z. Identification of novel protein-protein interactions of Yersinia pestis type III secretion system by yeast two hybrid system. PLoS One 2013; 8:e54121. [PMID: 23349800 PMCID: PMC3551969 DOI: 10.1371/journal.pone.0054121] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2012] [Accepted: 12/10/2012] [Indexed: 01/03/2023] Open
Abstract
Type III secretion system (T3SS) of the plague bacterium Y. pestis encodes a syringe-like structure consisting of more than 20 proteins, which can inject virulence effectors into host cells to modulate the cellular functions. Here in this report, interactions among the possible components in T3SS of Yersinia pestis were identified using yeast mating technique. A total of 57 genes, including all the pCD1-encoded genes except those involved in plasmid replication and partition, pseudogenes, and the putative transposase genes, were subjected to yeast mating analysis. 21 pairs of interaction proteins were identified, among which 9 pairs had been previously reported and 12 novel pairs were identified in this study. Six of them were tested by GST pull down assay, and interaction pairs of YscG-SycD, YscG-TyeA, YscI-YscF, and YopN-YpCD1.09c were successfully validated, suggesting that these interactions might play potential roles in function of Yersinia T3SS. Several potential new interactions among T3SS components could help to understand the assembly and regulation of Yersinia T3SS.
Collapse
Affiliation(s)
- Huiying Yang
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, China
| | - Yafang Tan
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, China
| | - Tingting Zhang
- Department of Clinical Medicine, College of Veterinary Medicine, Sichuan Agricultural University, Yaan, Sichuan, China
| | - Liujun Tang
- State Key Laboratory of Proteomics, Beijing Proteome Research Center, Beijing Institute of Radiation Medicine, Beijing, China
| | - Jian Wang
- State Key Laboratory of Proteomics, Beijing Proteome Research Center, Beijing Institute of Radiation Medicine, Beijing, China
| | - Yuehua Ke
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, China
| | - Zhaobiao Guo
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, China
| | - Xiaoming Yang
- State Key Laboratory of Proteomics, Beijing Proteome Research Center, Beijing Institute of Radiation Medicine, Beijing, China
| | - Ruifu Yang
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, China
| | - Zongmin Du
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, China
| |
Collapse
|
28
|
Protein export according to schedule: architecture, assembly, and regulation of type III secretion systems from plant- and animal-pathogenic bacteria. Microbiol Mol Biol Rev 2012; 76:262-310. [PMID: 22688814 DOI: 10.1128/mmbr.05017-11] [Citation(s) in RCA: 299] [Impact Index Per Article: 24.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Flagellar and translocation-associated type III secretion (T3S) systems are present in most gram-negative plant- and animal-pathogenic bacteria and are often essential for bacterial motility or pathogenicity. The architectures of the complex membrane-spanning secretion apparatuses of both systems are similar, but they are associated with different extracellular appendages, including the flagellar hook and filament or the needle/pilus structures of translocation-associated T3S systems. The needle/pilus is connected to a bacterial translocon that is inserted into the host plasma membrane and mediates the transkingdom transport of bacterial effector proteins into eukaryotic cells. During the last 3 to 5 years, significant progress has been made in the characterization of membrane-associated core components and extracellular structures of T3S systems. Furthermore, transcriptional and posttranscriptional regulators that control T3S gene expression and substrate specificity have been described. Given the architecture of the T3S system, it is assumed that extracellular components of the secretion apparatus are secreted prior to effector proteins, suggesting that there is a hierarchy in T3S. The aim of this review is to summarize our current knowledge of T3S system components and associated control proteins from both plant- and animal-pathogenic bacteria.
Collapse
|
29
|
Diepold A, Wiesand U, Amstutz M, Cornelis GR. Assembly of theYersiniainjectisome: the missing pieces. Mol Microbiol 2012; 85:878-92. [DOI: 10.1111/j.1365-2958.2012.08146.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
|
30
|
Structure–functional analysis of the Dictyoglomus cell envelope. Syst Appl Microbiol 2012; 35:279-90. [DOI: 10.1016/j.syapm.2012.06.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2011] [Revised: 06/18/2012] [Accepted: 06/19/2012] [Indexed: 11/23/2022]
|
31
|
Kosarewicz A, Königsmaier L, Marlovits TC. The blueprint of the type-3 injectisome. Philos Trans R Soc Lond B Biol Sci 2012; 367:1140-54. [PMID: 22411984 DOI: 10.1098/rstb.2011.0205] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Type-3 secretion systems are sophisticated syringe-like nanomachines present in many animal and plant Gram-negative pathogens. They are capable of translocating an arsenal of specific bacterial toxins (effector proteins) from the prokaryotic cytoplasm across the three biological membranes directly into the eukaryotic cytosol, some of which modulate host cell mechanisms for the benefit of the pathogen. They populate a particular biological niche, which is maintained by specific, pathogen-dependent effectors. In contrast, the needle complex, which is the central component of this specialized protein delivery machine, is structurally well-conserved. It is a large supramolecular cylindrical structure composed of multiple copies of a relatively small subset of proteins, is embedded in the bacterial membranes and protrudes from the pathogen's surface with a needle filament. A central channel traverses the entire needle complex, and serves as a hollow conduit for proteins destined to travel this secretion pathway. In the past few years, there has been a tremendous increase in an understanding on both the structural and the mechanistic level. This review will thus focus on new insights of this remarkable molecular machine.
Collapse
Affiliation(s)
- Agata Kosarewicz
- Research Institute of Molecular Pathology, Dr. Bohr Gasse 7, A-1030 Vienna, Austria
| | | | | |
Collapse
|
32
|
EscA is a crucial component of the type III secretion system of enteropathogenic Escherichia coli. J Bacteriol 2012; 194:2819-28. [PMID: 22447907 DOI: 10.1128/jb.00103-12] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
The virulence of many Gram-negative pathogens is associated with type III secretion systems (T3SSs), which deliver virulence effector proteins into the cytoplasm of host cells. Components of enteropathogenic Escherichia coli (EPEC) T3SS are encoded within the locus of enterocyte effacement (LEE). While most LEE-encoded T3SS proteins in EPEC have assigned names and functions, a few of them remain poorly characterized. Here, we studied a small LEE-encoded protein, Orf15, that shows no homology to other T3SS/flagellar proteins and is only present in attaching and effacing pathogens, including enterohemorrhagic E. coli and Citrobacter rodentium. Our findings demonstrated that it is essential for type III secretion (T3S) and that it is localized to the periplasm and associated with the inner membrane. Membrane association was driven by the N-terminal 19 amino acid residues, which were also shown to be essential for T3S. Consistent with its localization, Orf15 was found to interact with the EPEC T3SS outer membrane ring component, EscC, which was previously shown to be embedded within the outer membrane and protruding into the periplasmic space. Interestingly, we found that the predicted coiled-coil structure of Orf15 is critical for the protein's function. Overall, our findings suggest that Orf15 is a structural protein that contributes to the structural integrity of the T3S complex, and therefore we propose to rename it EscA.
Collapse
|
33
|
Müller SA, Engel A. Looking back at a quarter-century of research at the Maurice E. Müller Institute for Structural Biology. J Struct Biol 2011; 177:3-13. [PMID: 22115996 DOI: 10.1016/j.jsb.2011.11.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2011] [Revised: 11/04/2011] [Accepted: 11/05/2011] [Indexed: 10/15/2022]
Abstract
The Maurice E. Müller Institute, embedded in the infrastructure of the Biozentrum, University of Basel, was founded in 1985 and financed by the Maurice E. Müller Foundation of Switzerland. For 26 years its two founders, Ueli Aebi and Andreas Engel, pursued the vision of integrated structural biology. This paper reviews selected publications issuing from the Maurice E. Müller Institute for Structural Biology and marks the end of this era.
Collapse
Affiliation(s)
- Shirley A Müller
- Center for Cellular Imaging and Nano Analytics, Biozentrum, University of Basel, Mattenstrasse 26, CH-4058 Basel, Switzerland
| | | |
Collapse
|
34
|
Diepold A, Wiesand U, Cornelis GR. The assembly of the export apparatus (YscR,S,T,U,V) of the Yersinia type III secretion apparatus occurs independently of other structural components and involves the formation of an YscV oligomer. Mol Microbiol 2011; 82:502-14. [DOI: 10.1111/j.1365-2958.2011.07830.x] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
|
35
|
Korotkov KV, Gonen T, Hol WGJ. Secretins: dynamic channels for protein transport across membranes. Trends Biochem Sci 2011; 36:433-43. [PMID: 21565514 DOI: 10.1016/j.tibs.2011.04.002] [Citation(s) in RCA: 124] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2011] [Revised: 04/06/2011] [Accepted: 04/08/2011] [Indexed: 12/16/2022]
Abstract
Secretins form megadalton bacterial-membrane channels in at least four sophisticated multiprotein systems that are crucial for translocation of proteins and assembled fibers across the outer membrane of many species of bacteria. Secretin subunits contain multiple domains, which interact with numerous other proteins, including pilotins, secretion-system partner proteins, and exoproteins. Our understanding of the structure of secretins is rapidly progressing, and it is now recognized that features common to all secretins include a cylindrical arrangement of 12-15 subunits, a large periplasmic vestibule with a wide opening at one end and a periplasmic gate at the other. Secretins might also play a key role in the biogenesis of their cognate secretion systems.
Collapse
|
36
|
Tarry M, Jääskeläinen M, Paino A, Tuominen H, Ihalin R, Högbom M. The extra-membranous domains of the competence protein HofQ show DNA binding, flexibility and a shared fold with type I KH domains. J Mol Biol 2011; 409:642-53. [PMID: 21530539 DOI: 10.1016/j.jmb.2011.04.034] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2011] [Revised: 04/08/2011] [Accepted: 04/12/2011] [Indexed: 10/18/2022]
Abstract
Secretins form large oligomeric assemblies in the membrane that control both macromolecular secretion and uptake. Several Pasteurellaceae are naturally competent for transformation, but the mechanism for DNA assimilation is largely unknown. In Haemophilus influenzae, the secretin ComE has been demonstrated to be essential for DNA uptake. In closely related Aggregatibacter actinomycetemcomitans, an opportunistic pathogen in periodontitis, the ComE homolog HofQ is believed to be the outer membrane DNA translocase. Here, we report the structure of the extra-membranous domains of HofQ at 2.3 Å resolution by X-ray crystallography. We also show that the extra-membranous domains of HofQ are capable of DNA binding. The structure reveals two secretin-like folds, the first of which is formed by means of a domain swap. The second domain displays extensive structural similarity to K homology (KH) domains, including the presence of a GxxG motif, which is essential for the nucleotide-binding function of KH domains, suggesting a possible mechanism for DNA binding by HofQ. The data indicate a direct involvement in DNA acquisition and provide insight into the molecular basis for natural competence.
Collapse
Affiliation(s)
- Michael Tarry
- Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden
| | | | | | | | | | | |
Collapse
|
37
|
Burkhardt J, Vonck J, Averhoff B. Structure and function of PilQ, a secretin of the DNA transporter from the thermophilic bacterium Thermus thermophilus HB27. J Biol Chem 2011; 286:9977-84. [PMID: 21285351 DOI: 10.1074/jbc.m110.212688] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Secretins are a family of large bacterial outer membrane protein complexes mediating the transport of complex structures, such as type IV pili, DNA and filamentous phage, or various proteins, such as extracellular enzymes and pathogenicity determinants. PilQ of the thermophilic bacterium Thermus thermophilus HB27 is a member of the secretin family required for natural transformation. Here we report the isolation, structural, and functional analyses of a unique PilQ from T. thermophilus. Native PAGE, gel filtration chromatography, and electrophoretic mobility shift analyses indicated that PilQ forms a macromolecular homopolymeric complex that binds dsDNA. Electron microscopy showed that the PilQ complex is 15 nm wide and 34 nm long and consists of an extraordinary stable "cone" and "cup" structure and five ring structures with a large central channel. Moreover, the electron microscopic images together with secondary structure analyses combined with structural data of type II protein secretion system and type III protein secretion system secretins suggest that the individual rings are formed by conserved domains of alternating α-helices and β-sheets. The unprecedented length of the PilQ complex correlated well with the distance between the inner and outer membrane of T. thermophilus. Indeed, PilQ was found immunologically in both membranes, indicating that the PilQ complex spans the entire cell periphery of T. thermophilus. This is consistent with the hypothesis that PilQ accommodates a PilA4 comprising pseudopilus mediating DNA transport across the outer membrane and periplasmic space in a single-step process.
Collapse
Affiliation(s)
- Janin Burkhardt
- Molecular Microbiology and Bioenergetics, Institute of Molecular Biosciences, Goethe University, Max-von-Laue-Strasse 9, D-60438 Frankfurt/Main, Germany
| | | | | |
Collapse
|
38
|
Cornelis GR. The type III secretion injectisome, a complex nanomachine for intracellular 'toxin' delivery. Biol Chem 2011; 391:745-51. [PMID: 20482311 DOI: 10.1515/bc.2010.079] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The type III secretion injectisome is a nanomachine that delivers bacterial proteins into the cytosol of eukaryotic target cells. It consists of a cylindrical basal structure spanning the two bacterial membranes and the peptidoglycan, connected to a hollow needle, eventually followed by a filament (animal pathogens) or to a long pilus (plant pathogens). Export employs a type III pathway. During assembly, all the protein subunits of external elements are sequentially exported by the basal structure itself, implying that the export apparatus can switch its substrate specificity over time. The length of the needle is controlled by a protein that it also secreted during assembly and presumably acts as a molecular ruler.
Collapse
Affiliation(s)
- Guy R Cornelis
- Biozentrum der Universität Basel, CH-4056 Basel, Switzerland.
| |
Collapse
|
39
|
Outer membrane translocons: structural insights into channel formation. Trends Microbiol 2010; 19:40-8. [PMID: 21130656 DOI: 10.1016/j.tim.2010.10.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2010] [Revised: 10/18/2010] [Accepted: 10/29/2010] [Indexed: 01/26/2023]
Abstract
Gram-negative bacteria need to maintain the integrity of their outer membrane while also regulating the secretion of toxins and other macromolecules. A variety of dedicated outer membrane proteins (OMPs) facilitate this process. Recent structural work has shown that some of these proteins adopt classical β-barrel transmembrane structures and rely on structural changes within the barrel lumen to allow passage of substrate proteins. Other secretion systems have OMP components which use transmembrane α-helices and appear to function in a different way. Here we review a selection of recent structural studies which have major ramifications for our understanding of the passage of macromolecules across the outer membrane.
Collapse
|
40
|
Worrall LJ, Lameignere E, Strynadka NCJ. Structural overview of the bacterial injectisome. Curr Opin Microbiol 2010; 14:3-8. [PMID: 21112241 DOI: 10.1016/j.mib.2010.10.009] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2010] [Revised: 10/27/2010] [Accepted: 10/29/2010] [Indexed: 12/30/2022]
Abstract
The bacterial injectisome is a specialized protein-export system utilized by many pathogenic Gram-negative bacteria for the delivery of virulence proteins into the hosts they infect. This needle-like molecular nanomachine comprises >20 proteins creating a continuous passage from bacterial to host cytoplasm. The last few years have witnessed significant progress in our understanding of the structure of the injectisome with important contributions from X-ray crystallography, NMR and EM. This review will present the current state of the structure of the injectisome with particular focus on the molecular structures of individual components and how these assemble together in a functioning T3SS.
Collapse
Affiliation(s)
- Liam J Worrall
- Department of Biochemistry and Molecular Biology, University of British Columbia, Life Sciences Centre, 2350 Health Sciences Mall Vancouver, British Columbia, Canada
| | | | | |
Collapse
|
41
|
Structure of the cholera toxin secretion channel in its closed state. Nat Struct Mol Biol 2010; 17:1226-32. [PMID: 20852644 PMCID: PMC2950906 DOI: 10.1038/nsmb.1910] [Citation(s) in RCA: 119] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2010] [Accepted: 07/27/2010] [Indexed: 01/26/2023]
Abstract
The type II secretion system (T2SS) is a macromolecular complex spanning the inner and outer membranes of Gram-negative bacteria. Remarkably, the T2SS secretes folded proteins, including multimeric assemblies such as cholera toxin and heat-labile enterotoxin from Vibrio cholerae and enterotoxigenic Escherichia coli, respectively. The major outer membrane T2SS protein is the 'secretin' GspD. Cryo-EM reconstruction of the V. cholerae secretin at 19-Å resolution reveals a dodecameric structure reminiscent of a barrel, with a large channel at its center that contains a closed periplasmic gate. The GspD periplasmic domain forms a vestibule with a conserved constriction, and it binds to a pentameric exoprotein and to the trimeric tip of the T2SS pseudopilus. By combining our results with structures of the cholera toxin and T2SS pseudopilus tip, we provide a structural basis for a possible secretion mechanism of the T2SS.
Collapse
|
42
|
Diepold A, Amstutz M, Abel S, Sorg I, Jenal U, Cornelis GR. Deciphering the assembly of the Yersinia type III secretion injectisome. EMBO J 2010; 29:1928-40. [PMID: 20453832 DOI: 10.1038/emboj.2010.84] [Citation(s) in RCA: 126] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2010] [Accepted: 04/13/2010] [Indexed: 01/05/2023] Open
Abstract
The assembly of the Yersinia enterocolitica type III secretion injectisome was investigated by grafting fluorescent proteins onto several components, YscC (outer-membrane (OM) ring), YscD (forms the inner-membrane (IM) ring together with YscJ), YscN (ATPase), and YscQ (putative C ring). The recombinant injectisomes were functional and appeared as fluorescent spots at the cell periphery. Epistasis experiments with the hybrid alleles in an array of injectisome mutants revealed a novel outside-in assembly order: whereas YscC formed spots in the absence of any other structural protein, formation of YscD foci required YscC, but not YscJ. We therefore propose that the assembly starts with YscC and proceeds through the connector YscD to YscJ, which was further corroborated by co-immunoprecipitation experiments. Completion of the membrane rings allowed the subsequent assembly of cytosolic components. YscN and YscQ attached synchronously, requiring each other, the interacting proteins YscK and YscL, but no further injectisome component for their assembly. These results show that assembly is initiated by the formation of the OM ring and progresses inwards to the IM ring and, finally, to a large cytosolic complex.
Collapse
Affiliation(s)
- Andreas Diepold
- Infection Biology, Biozentrum der Universität Basel, Basel, Switzerland
| | | | | | | | | | | |
Collapse
|
43
|
Login FH, Fries M, Wang X, Pickersgill RW, Shevchik VE. A 20-residue peptide of the inner membrane protein OutC mediates interaction with two distinct sites of the outer membrane secretin OutD and is essential for the functional type II secretion system in Erwinia chrysanthemi. Mol Microbiol 2010; 76:944-55. [PMID: 20444086 DOI: 10.1111/j.1365-2958.2010.07149.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The type II secretion system (T2SS) is widely exploited by proteobacteria to secrete enzymes and toxins involved in bacterial survival and pathogenesis. The outer membrane pore formed by the secretin OutD and the inner membrane protein OutC are two key components of the secretion complex, involved in secretion specificity. Here, we show that the periplasmic regions of OutC and OutD interact directly and map the interaction site of OutC to a 20-residue peptide named OutCsip (secretin interacting peptide, residues 139-158). This peptide interacts in vitro with two distinct sites of the periplasmic region of OutD, one located on the N0 subdomain and another overlapping the N2-N3' subdomains. The two interaction sites of OutD have different modes of binding to OutCsip. A single substitution, V143S, located within OutCsip prevents its interaction with one of the two binding sites of OutD and fully inactivates the T2SS. We show that the N0 subdomain of OutD interacts also with a second binding site within OutC located in the region proximal to the transmembrane segment. We suggest that successive interactions between these distinct regions of OutC and OutD may have functional importance in switching the secretion machine.
Collapse
Affiliation(s)
- Frédéric H Login
- Université de Lyon, F-69003, Université Lyon 1, Lyon, F-69622, INSA-Lyon, Villeurbanne, F-69621, CNRS, UMR5240, Microbiologie Adaptation et Pathogénie, Lyon, F-69622, France
| | | | | | | | | |
Collapse
|
44
|
Type III secretion systems shape up as they ship out. Curr Opin Microbiol 2009; 13:47-52. [PMID: 20015680 DOI: 10.1016/j.mib.2009.11.001] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2009] [Accepted: 11/14/2009] [Indexed: 11/23/2022]
Abstract
Virulence associated protein type III secretion systems (T3SSs) are intricately structured organic nanosyringes that achieve the translocation of bacterial proteins from the prokaryotic cytoplasm across three membranes into the host cytosol. The substrates for these systems number in the hundreds, with remarkably diverse biological activities, modulating host cell biology for the benefit of the pathogen. Although there has been tremendous progress on the structure and function of the T3SS substrates, there has been comparatively little progress on the much more highly conserved secretion apparatus itself. This review summarizes recent advances in the field of structural microbiology that have begun to address this shortcoming, finally bringing to bear the power of structural biology to this central virulence system of Gram-negative bacterial pathogens.
Collapse
|
45
|
Mapingire OS, Henderson NS, Duret G, Thanassi DG, Delcour AH. Modulating effects of the plug, helix, and N- and C-terminal domains on channel properties of the PapC usher. J Biol Chem 2009; 284:36324-36333. [PMID: 19850919 DOI: 10.1074/jbc.m109.055798] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The chaperone/usher system is one of the best characterized pathways for protein secretion and assembly of cell surface appendages in Gram-negative bacteria. In particular, this pathway is used for biogenesis of the P pilus, a key virulence factor used by uropathogenic Escherichia coli to adhere to the host urinary tract. The P pilus individual subunits bound to the periplasmic chaperone PapD are delivered to the outer membrane PapC usher, which serves as an assembly platform for subunit incorporation into the pilus and secretion of the pilus fiber to the cell surface. PapC forms a dimeric, twin pore complex, with each monomer composed of a 24-stranded transmembrane beta-barrel channel, an internal plug domain that occludes the channel, and globular N- and C-terminal domains that are located in the periplasm. Here we have used planar lipid bilayer electrophysiology to characterize the pore properties of wild type PapC and domain deletion mutants for the first time. The wild type pore is closed most of the time but displays frequent short-lived transitions to various open states. In comparison, PapC mutants containing deletions of the plug domain, an alpha-helix that caps the plug domain, or the N- and C-terminal domains form channels with higher open probability but still exhibiting dynamic behavior. Removal of the plug domain results in a channel with extremely large conductance. These observations suggest that the plug gates the usher channel closed and that the periplasmic domains and alpha-helix function to modulate the gating activity of the PapC twin pore.
Collapse
Affiliation(s)
- Owen S Mapingire
- Department of Biology and Biochemistry, University of Houston, Houston, Texas 77204
| | - Nadine S Henderson
- Center for Infectious Diseases, Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, New York 11794
| | - Guillaume Duret
- Department of Biology and Biochemistry, University of Houston, Houston, Texas 77204
| | - David G Thanassi
- Center for Infectious Diseases, Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, New York 11794.
| | - Anne H Delcour
- Department of Biology and Biochemistry, University of Houston, Houston, Texas 77204.
| |
Collapse
|
46
|
Three-dimensional reconstruction of the Shigella T3SS transmembrane regions reveals 12-fold symmetry and novel features throughout. Nat Struct Mol Biol 2009; 16:477-85. [PMID: 19396171 PMCID: PMC2681179 DOI: 10.1038/nsmb.1599] [Citation(s) in RCA: 99] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2008] [Accepted: 04/03/2009] [Indexed: 01/03/2023]
Abstract
Type III secretion systems (T3SSs) mediate bacterial protein translocation into eukaryotic cells, a process essential for virulence of many Gram-negative pathogens. They are composed of a cytoplasmic secretion machinery and a base that bridges both bacterial membranes, into which a hollow, external needle is embedded. When isolated, the latter two parts are termed the 'needle complex'. An incomplete understanding of the structure of the needle complex has hampered studies of T3SS function. To estimate the stoichiometry of its components, we measured the mass of its subdomains by scanning transmission electron microscopy (STEM). We determined subunit symmetries by analysis of top and side views within negatively stained samples in low-dose transmission electron microscopy (TEM). Application of 12-fold symmetry allowed generation of a 21-25-A resolution, three-dimensional reconstruction of the needle complex base, revealing many new features and permitting tentative docking of the crystal structure of EscJ, an inner membrane component.
Collapse
|
47
|
A conserved structural motif mediates formation of the periplasmic rings in the type III secretion system. Nat Struct Mol Biol 2009; 16:468-76. [PMID: 19396170 DOI: 10.1038/nsmb.1603] [Citation(s) in RCA: 157] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2008] [Accepted: 04/08/2009] [Indexed: 11/09/2022]
Abstract
The type III secretion system (T3SS) is a macromolecular 'injectisome' that allows bacterial pathogens to transport virulence proteins into the eukaryotic host cell. This macromolecular complex is composed of connected ring-like structures that span both bacterial membranes. The crystal structures of the periplasmic domain of the outer membrane secretin EscC and the inner membrane protein PrgH reveal the conservation of a modular fold among the three proteins that form the outer membrane and inner membrane rings of the T3SS. This leads to the hypothesis that this conserved fold provides a common ring-building motif that allows for the assembly of the variably sized outer membrane and inner membrane rings characteristic of the T3SS. Using an integrated structural and experimental approach, we generated ring models for the periplasmic domain of EscC and placed them in the context of the assembled T3SS, providing evidence for direct interaction between the outer membrane and inner membrane ring components and an unprecedented span of the outer membrane secretin.
Collapse
|
48
|
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
| | | | | | | | | |
Collapse
|
49
|
Meng G, Fronzes R, Chandran V, Remaut H, Waksman G. Protein oligomerization in the bacterial outer membrane (Review). Mol Membr Biol 2009; 26:136-45. [PMID: 19225986 DOI: 10.1080/09687680802712422] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The formation of homo-oligomeric assemblies is a well-established characteristic of many soluble proteins and enzymes. Oligomerization has been shown to increase protein stability, allow allosteric cooperativity, shape reaction compartments and provide multivalent interaction sites in soluble proteins. In comparison, our understanding of the prevalence and reasons behind protein oligomerization in membrane proteins is relatively sparse. Recent progress in structural biology of bacterial outer membrane proteins has suggested that oligomerization may be as common and versatile as in soluble proteins. Here we review the current understanding of oligomerization in the bacterial outer membrane from a structural and functional point of view.
Collapse
Affiliation(s)
- Guoyu Meng
- Institute of Structural and Molecular Biology, University College London and Birkbeck College, London, UK
| | | | | | | | | |
Collapse
|
50
|
Engel A. Chapter 9 Scanning Transmission Electron Microscopy. ACTA ACUST UNITED AC 2009. [DOI: 10.1016/s1076-5670(09)59009-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/25/2023]
|