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Tassinari M, Rudzite M, Filloux A, Low HH. Assembly mechanism of a Tad secretion system secretin-pilotin complex. Nat Commun 2023; 14:5643. [PMID: 37704603 PMCID: PMC10499894 DOI: 10.1038/s41467-023-41200-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2023] [Accepted: 08/25/2023] [Indexed: 09/15/2023] Open
Abstract
The bacterial Tight adherence Secretion System (TadSS) assembles surface pili that drive cell adherence, biofilm formation and bacterial predation. The structure and mechanism of the TadSS is mostly unknown. This includes characterisation of the outer membrane secretin through which the pilus is channelled and recruitment of its pilotin. Here we investigate RcpA and TadD lipoprotein from Pseudomonas aeruginosa. Light microscopy reveals RcpA colocalising with TadD in P. aeruginosa and when heterologously expressed in Escherichia coli. We use cryogenic electron microscopy to determine how RcpA and TadD assemble a secretin channel with C13 and C14 symmetries. Despite low sequence homology, we show that TadD shares a similar fold to the type 4 pilus system pilotin PilF. We establish that the C-terminal four residues of RcpA bind TadD - an interaction essential for secretin formation. The binding mechanism between RcpA and TadD appears distinct from known secretin-pilotin pairings in other secretion systems.
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Affiliation(s)
- Matteo Tassinari
- Department of Infectious Disease, Imperial College, London, SW7 2AZ, UK
- Human Technopole, Milan, Italy
| | - Marta Rudzite
- Department of Life Sciences, Imperial College, London, SW7 2AZ, UK
| | - Alain Filloux
- Department of Life Sciences, Imperial College, London, SW7 2AZ, UK
- Singapore Centre for Environmental Life Sciences Engineering, Nanyang Technological University, Singapore, Singapore
| | - Harry H Low
- Department of Infectious Disease, Imperial College, London, SW7 2AZ, UK.
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2
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Meir A, Macé K, Vegunta Y, Williams SM, Waksman G. Substrate recruitment mechanism by gram-negative type III, IV, and VI bacterial injectisomes. Trends Microbiol 2023; 31:916-932. [PMID: 37085348 DOI: 10.1016/j.tim.2023.03.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2022] [Revised: 03/09/2023] [Accepted: 03/13/2023] [Indexed: 04/23/2023]
Abstract
Bacteria use a wide arsenal of macromolecular substrates (DNA and proteins) to interact with or infect prokaryotic and eukaryotic cells. To do so, they utilize substrate-injecting secretion systems or injectisomes. However, prior to secretion, substrates must be recruited to specialized recruitment platforms and then handed over to the secretion apparatus for secretion. In this review, we provide an update on recent advances in substrate recruitment and delivery by gram-negative bacterial recruitment platforms associated with Type III, IV, and VI secretion systems.
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Affiliation(s)
- Amit Meir
- Institute of Structural and Molecular Biology, Birkbeck and UCL, Malet Street, London WC1E 7HX, UK; Current address: MRC Centre for Virus Research, School of Infection and Immunity, University of Glasgow, Glasgow, UK.
| | - Kévin Macé
- Institute of Structural and Molecular Biology, Birkbeck and UCL, Malet Street, London WC1E 7HX, UK
| | - Yogesh Vegunta
- Institute of Structural and Molecular Biology, Birkbeck and UCL, Malet Street, London WC1E 7HX, UK
| | - Sunanda M Williams
- Institute of Structural and Molecular Biology, Birkbeck and UCL, Malet Street, London WC1E 7HX, UK
| | - Gabriel Waksman
- Institute of Structural and Molecular Biology, Birkbeck and UCL, Malet Street, London WC1E 7HX, UK; Institute of Structural and Molecular Biology, University College London, Gower Street, London WC1E 6BT, UK.
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3
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Bcr4 Is a Chaperone for the Inner Rod Protein in the Bordetella Type III Secretion System. Microbiol Spectr 2022; 10:e0144322. [PMID: 36040173 PMCID: PMC9603008 DOI: 10.1128/spectrum.01443-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Bordetella bronchiseptica injects virulence proteins called effectors into host cells via a type III secretion system (T3SS) conserved among many Gram-negative bacteria. Small proteins called chaperones are required to stabilize some T3SS components or localize them to the T3SS machinery. In a previous study, we identified a chaperone-like protein named Bcr4 that regulates T3SS activity in B. bronchiseptica. Bcr4 does not show strong sequence similarity to well-studied T3SS proteins of other bacteria, and its function remains to be elucidated. Here, we investigated the mechanism by which Bcr4 controls T3SS activity. A pulldown assay revealed that Bcr4 interacts with BscI, based on its homology to other bacterial proteins, to be an inner rod protein of the T3SS machinery. An additional pulldown assay using truncated Bcr4 derivatives and secretion profiles of B. bronchiseptica producing truncated Bcr4 derivatives showed that the Bcr4 C-terminal region is necessary for the interaction with BscI and activation of the T3SS. Moreover, the deletion of BscI abolished the secretion of type III secreted proteins from B. bronchiseptica and the translocation of a cytotoxic effector into cultured mammalian cells. Finally, we show that BscI is unstable in the absence of Bcr4. These results suggest that Bcr4 supports the construction of the T3SS machinery by stabilizing BscI. This is the first demonstration of a chaperone for the T3SS inner rod protein among the virulence bacteria possessing the T3SS. IMPORTANCE The type III secretion system (T3SS) is a needle-like complex that projects outward from bacterial cells. Bordetella bronchiseptica uses the T3SS to inject virulence proteins into host cells. Our previous study reported that a protein named Bcr4 is essential for the secretion of virulence proteins from B. bronchiseptica bacterial cells and delivery through the T3SS. Because other bacteria lack a Bcr4 homologue, the function of Bcr4 has not been elucidated. In this study, we discovered that Bcr4 interacts with BscI, a component of the T3SS machinery. We show that a B. bronchiseptica BscI-deficient strain was unable to secrete type III secreted proteins. Furthermore, in a B. bronchiseptica strain that overproduces T3SS component proteins, Bcr4 is required to maintain BscI in bacterial cells. These results suggest that Bcr4 stabilizes BscI to allow construction of the T3SS in B. bronchiseptica.
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Secreted in a Type III Secretion System-Dependent Manner, EsaH and EscE Are the Cochaperones of the T3SS Needle Protein EsaG of Edwardsiella piscicida. mBio 2022; 13:e0125022. [PMID: 35861543 PMCID: PMC9426511 DOI: 10.1128/mbio.01250-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The intracellular EscE protein tightly controls the secretion of the type III secretion system (T3SS) middle and late substrates in Edwardsiella piscicida. However, the regulation of secretion by EscE is incompletely understood. In this work, we reveal that EscE interacts with EsaH and EsaG. The crystal structures of the EscE-EsaH complex and EscE-EsaG-EsaH complex were resolved at resolutions of 1.4 Å and 1.8 Å, respectively. EscE and EsaH form a hydrophobic groove to engulf the C-terminal region of EsaG (56 to 73 amino acids [aa]), serving as the cochaperones of T3SS needle protein EsaG in E. piscicida. V61, K62, M64, and M65 of EsaG play a pivotal role in maintaining the conformation of the ternary complex of EscE-EsaG-EsaH, thereby maintaining the stability of EsaG. An in vivo experiment revealed that EscE and EsaH stabilize each other, and both of them stabilize EsaG. Meanwhile, either EscE or EsaH can be secreted through the T3SS. The secondary structure of EsaH lacks the fourth and fifth α helices presented in its homologs PscG, YscG, and AscG. Insertion of the α4 and α5 helices of PscG or swapping the N-terminal 25 aa of PscG with those of EsaH starkly decreases the protein level of the chimeric EsaH, resulting in instability of EsaG and deactivation of the T3SS. To the best of our knowledge, these data represent the first reported structure of the T3SS needle complex of pathogens from Enterobacteriaceae and the first evidence for the secretion of T3SS needle chaperones. IMPORTANCE Edwardsiella piscicida causes severe hemorrhagic septicemia in fish. Inactivation of the type III secretion system (T3SS) increases its 50% lethal dose (LD50) by ~10 times. The secretion of T3SS middle and late substrates in E. piscicida is tightly controlled by the intracellular steady-state protein level of EscE, but the mechanism is incompletely understood. In this study, EscE was found to interact with and stabilize EsaH in E. piscicida. The EscE-EsaH complex is structurally analogous to T3SS needle chaperones. Further study revealed that EscE and EsaH form a hydrophobic groove to engulf the C-terminal region of EsaG, serving as the cochaperones stabilizing the T3SS needle protein EsaG. Interestingly, both EscE and EsaH are secreted. Our study reveals that the EscE-EsaH complex controls T3SS protein secretion by stabilizing EsaG, whose secretion in turn leads to the secretion of the middle and late T3SS substrates.
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RNA thermometer-coordinated assembly of the Yersinia injectisome. J Mol Biol 2022; 434:167667. [PMID: 35667470 DOI: 10.1016/j.jmb.2022.167667] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Revised: 05/20/2022] [Accepted: 05/30/2022] [Indexed: 11/21/2022]
Abstract
The type III secretion system (T3SS) is indispensable for successful host cell infection by many Gram-negative pathogens. The molecular syringe delivers effector proteins that suppress the host immune response. Synthesis of T3SS components in Yersinia pseudotuberculosis relies on host body temperature, which induces the RNA thermometer (RNAT)-controlled translation of lcrF coding for a virulence master regulator that activates transcription of the T3SS regulon. The assembly of the secretion machinery follows a strict coordinated succession referred to as outside-in assembly, in which the membrane ring complex and the export apparatus represent the nucleation points. Two components essential for the initial assembly are YscJ and YscT. While YscJ connects the membrane ring complex with the export apparatus in the inner membrane, YscT is required for a functional export apparatus. Previous transcriptome-wide RNA structuromics data suggested the presence of unique intercistronic RNATs upstream of yscJ and yscT. Here, we show by reporter gene fusions that both upstream regions confer translational control. Moreover, we demonstrate the temperature-induced opening of the Shine-Dalgarno region, which facilitates ribosome binding, by in vitro structure probing and toeprinting methods. Rationally designed thermostable RNAT variants of the yscJ and yscT thermometers confirmed their physiological relevance with respect to T3SS assembly and host infection. Since we have shown in a recent study that YopN, the gatekeeper of type III secretion, also is under RNAT control, it appears that the synthesis, assembly and functionality of the Yersinia T3S machinery is coordinated by RNA-based temperature sensors at multiple levels.
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6
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Gilzer D, Schreiner M, Niemann HH. Direct interaction of a chaperone-bound type III secretion substrate with the export gate. Nat Commun 2022; 13:2858. [PMID: 35654781 PMCID: PMC9163089 DOI: 10.1038/s41467-022-30487-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Accepted: 04/29/2022] [Indexed: 12/12/2022] Open
Abstract
Several gram-negative bacteria employ type III secretion systems (T3SS) to inject effector proteins into eukaryotic host cells directly from the bacterial cytoplasm. The export gate SctV (YscV in Yersinia) binds substrate:chaperone complexes such as YscX:YscY, which are essential for formation of a functional T3SS. Here, we present structures of the YscX:YscY complex alone and bound to nonameric YscV. YscX binds its chaperone YscY at two distinct sites, resembling the heterotrimeric complex of the T3SS needle subunit with its chaperone and co-chaperone. In the ternary complex the YscX N-terminus, which mediates YscX secretion, occupies a binding site within one YscV that is also used by flagellar chaperones, suggesting the interaction's importance for substrate recognition. The YscX C-terminus inserts between protomers of the YscV ring where the stalk protein binds to couple YscV to the T3SS ATPase. This primary YscV-YscX interaction is essential for the formation of a secretion-competent T3SS.
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Affiliation(s)
- Dominic Gilzer
- Department of Chemistry, Bielefeld University, Universitaetstrasse 25, 33615, Bielefeld, Germany
| | - Madeleine Schreiner
- Department of Chemistry, Bielefeld University, Universitaetstrasse 25, 33615, Bielefeld, Germany
| | - Hartmut H Niemann
- Department of Chemistry, Bielefeld University, Universitaetstrasse 25, 33615, Bielefeld, Germany.
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7
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Dey S, Chakravarty A, Guha Biswas P, De Guzman RN. The type III secretion system needle, tip, and translocon. Protein Sci 2019; 28:1582-1593. [PMID: 31301256 DOI: 10.1002/pro.3682] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2019] [Revised: 07/05/2019] [Accepted: 07/08/2019] [Indexed: 11/06/2022]
Abstract
Many Gram-negative bacteria pathogenic to plants and animals deploy the type III secretion system (T3SS) to inject virulence factors into their hosts. All bacteria that rely on the T3SS to cause infectious diseases in humans have developed antibiotic resistance. The T3SS is an attractive target for developing new antibiotics because it is essential in virulence, and part of its structural component is exposed on the bacterial surface. The structural component of the T3SS is the needle apparatus, which is assembled from over 20 different proteins and consists of a base, an extracellular needle, a tip, and a translocon. This review summarizes the current knowledge on the structure and assembly of the needle, tip, and translocon.
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Affiliation(s)
- Supratim Dey
- Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas
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8
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Lombardi C, Tolchard J, Bouillot S, Signor L, Gebus C, Liebl D, Fenel D, Teulon JM, Brock J, Habenstein B, Pellequer JL, Faudry E, Loquet A, Attrée I, Dessen A, Job V. Structural and Functional Characterization of the Type Three Secretion System (T3SS) Needle of Pseudomonas aeruginosa. Front Microbiol 2019; 10:573. [PMID: 31001211 PMCID: PMC6455054 DOI: 10.3389/fmicb.2019.00573] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Accepted: 03/05/2019] [Indexed: 01/23/2023] Open
Abstract
The type three secretion system (T3SS) is a macromolecular protein nano-syringe used by different bacterial pathogens to inject effectors into host cells. The extracellular part of the syringe is a needle-like filament formed by the polymerization of a 9-kDa protein whose structure and proper localization on the bacterial surface are key determinants for efficient toxin injection. Here, we combined in vivo, in vitro, and in silico approaches to characterize the Pseudomonas aeruginosa T3SS needle and its major component PscF. Using a combination of mutagenesis, phenotypic analyses, immunofluorescence, proteolysis, mass spectrometry, atomic force microscopy, electron microscopy, and molecular modeling, we propose a model of the P. aeruginosa needle that exposes the N-terminal region of each PscF monomer toward the outside of the filament, while the core of the fiber is formed by the C-terminal helix. Among mutations introduced into the needle protein PscF, D76A, and P47A/Q54A caused a defect in the assembly of the needle on the bacterial surface, although the double mutant was still cytotoxic on macrophages in a T3SS-dependent manner and formed filamentous structures in vitro. These results suggest that the T3SS needle of P. aeruginosa displays an architecture that is similar to that of other bacterial needles studied to date and highlight the fact that small, targeted perturbations in needle assembly can inhibit T3SS function. Therefore, the T3SS needle represents an excellent drug target for small molecules acting as virulence blockers that could disrupt pathogenesis of a broad range of bacteria.
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Affiliation(s)
- Charlotte Lombardi
- Univ. Grenoble Alpes, CEA, CNRS, Institut de Biologie Structurale (IBS), Grenoble, France
| | - James Tolchard
- Institute of Chemistry and Biology of Membranes and Nanoobjects, Institut Européen de Chimie et Biologie (CBMN), UMR5248 CNRS, University of Bordeaux, Pessac, France
| | - Stephanie Bouillot
- Univ. Grenoble Alpes, Bacterial Pathogenesis and Cellular Responses Group, U1036 INSERM, ERL5261 CNRS, CEA, Grenoble, France
| | - Luca Signor
- Univ. Grenoble Alpes, CEA, CNRS, Institut de Biologie Structurale (IBS), Grenoble, France
| | - Caroline Gebus
- Univ. Grenoble Alpes, Bacterial Pathogenesis and Cellular Responses Group, U1036 INSERM, ERL5261 CNRS, CEA, Grenoble, France
| | - David Liebl
- Univ. Grenoble Alpes, Bacterial Pathogenesis and Cellular Responses Group, U1036 INSERM, ERL5261 CNRS, CEA, Grenoble, France
| | - Daphna Fenel
- Univ. Grenoble Alpes, CEA, CNRS, Institut de Biologie Structurale (IBS), Grenoble, France
| | - Jean-Marie Teulon
- Univ. Grenoble Alpes, CEA, CNRS, Institut de Biologie Structurale (IBS), Grenoble, France
| | - Juliane Brock
- Univ. Grenoble Alpes, CEA, CNRS, Institut de Biologie Structurale (IBS), Grenoble, France
| | - Birgit Habenstein
- Institute of Chemistry and Biology of Membranes and Nanoobjects, Institut Européen de Chimie et Biologie (CBMN), UMR5248 CNRS, University of Bordeaux, Pessac, France
| | - Jean-Luc Pellequer
- Univ. Grenoble Alpes, CEA, CNRS, Institut de Biologie Structurale (IBS), Grenoble, France
| | - Eric Faudry
- Univ. Grenoble Alpes, Bacterial Pathogenesis and Cellular Responses Group, U1036 INSERM, ERL5261 CNRS, CEA, Grenoble, France
| | - Antoine Loquet
- Institute of Chemistry and Biology of Membranes and Nanoobjects, Institut Européen de Chimie et Biologie (CBMN), UMR5248 CNRS, University of Bordeaux, Pessac, France
| | - Ina Attrée
- Univ. Grenoble Alpes, Bacterial Pathogenesis and Cellular Responses Group, U1036 INSERM, ERL5261 CNRS, CEA, Grenoble, France
| | - Andréa Dessen
- Univ. Grenoble Alpes, CEA, CNRS, Institut de Biologie Structurale (IBS), Grenoble, France.,Brazilian Biosciences National Laboratory (LNBio), Centro Nacional de Pesquisa em Energia e Materiais (CNPEM), Campinas, Brazil
| | - Viviana Job
- Univ. Grenoble Alpes, CEA, CNRS, Institut de Biologie Structurale (IBS), Grenoble, France.,Univ. Grenoble Alpes, Bacterial Pathogenesis and Cellular Responses Group, U1036 INSERM, ERL5261 CNRS, CEA, Grenoble, France
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9
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Takaya A, Takeda H, Tashiro S, Kawashima H, Yamamoto T. Chaperone-mediated secretion switching from early to middle substrates in the type III secretion system encoded by Salmonella pathogenicity island 2. J Biol Chem 2019; 294:3783-3793. [PMID: 30651351 DOI: 10.1074/jbc.ra118.005072] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Revised: 01/07/2019] [Indexed: 11/06/2022] Open
Abstract
The bacterial type III secretion system (T3SS) delivers virulence proteins, called effectors, into eukaryotic cells. T3SS comprises a transmembrane secretion apparatus and a complex network of specialized chaperones that target protein substrates to this secretion apparatus. However, the regulation of secretion switching from early (needle and inner rod) to middle (tip/filament and translocators) substrates is incompletely understood. Here, we investigated chaperone-mediated secretion switching from early to middle substrates in the T3SS encoded by Salmonella pathogenicity island 2 (SPI2), essential for systemic infection. Our findings revealed that the protein encoded by ssaH regulates the secretion of an inner rod and early substrate, SsaI. Structural modeling revealed that SsaH is structurally similar to class III chaperones, known to associate with proteins in various pathogenic bacteria. The SPI2 protein SsaE was identified as a class V chaperone homolog and partner of SsaH. A pulldown analysis disclosed that SsaH and SsaE form a heterodimer, which interacted with another early substrate, the needle protein SsaG. Moreover, SsaE also helped stabilize SsaH and a middle substrate, SseB. We also found that SsaE regulates cellular SsaH levels to translocate the early substrates SsaG and SsaI and then promotes the translocation of SseB by stabilizing it. In summary, our results indicate that the class III chaperone SsaH facilitates SsaI secretion, and a heterodimer of SsaH and the type V chaperone SsaE then switches secretion to SsaG. This is the first report of a chaperone system that regulates both early and middle substrates during substrate switching for T3SS assembly.
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Affiliation(s)
- Akiko Takaya
- From the Laboratory of Microbiology and Immunology, Graduate School of Pharmaceutical Sciences, Chiba University, Chiba 260-8675, Japan and
| | - Hikari Takeda
- From the Laboratory of Microbiology and Immunology, Graduate School of Pharmaceutical Sciences, Chiba University, Chiba 260-8675, Japan and
| | - Shogo Tashiro
- From the Laboratory of Microbiology and Immunology, Graduate School of Pharmaceutical Sciences, Chiba University, Chiba 260-8675, Japan and
| | - Hiroto Kawashima
- From the Laboratory of Microbiology and Immunology, Graduate School of Pharmaceutical Sciences, Chiba University, Chiba 260-8675, Japan and
| | - Tomoko Yamamoto
- Medical Mycology Research Center, Chiba University, Chiba 260-8673, Japan
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Habenstein B, El Mammeri N, Tolchard J, Lamon G, Tawani A, Berbon M, Loquet A. Structures of Type III Secretion System Needle Filaments. Curr Top Microbiol Immunol 2019; 427:109-131. [PMID: 31974760 DOI: 10.1007/82_2019_192] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Among the Gram-negative bacterial secretion systems, type III secretion systems (T3SS) possess a unique extracellular molecular apparatus called the needle. This macromolecular protein assembly is a nanometre-size filament formed by the helical arrangement of hundreds of copies of a single, small protein, which is highly conserved between T3SSs from animal to plant bacterial pathogens. The needle filament forms a hollow tube with a channel ~20 Å in diameter that serves as a conduit for proteins secreted into the targeted host cell. In the past ten years, technical breakthroughs in biophysical techniques such as cryo-electron microscopy (cryo-EM) and solid-state NMR (SSNMR) spectroscopy have uncovered atomic resolution details about the T3SS needle assembly. Several high-resolution structures of Salmonella typhimurium and Shigella flexneri T3SS needles have been reported demonstrating a common structural fold. These structural models have been used to explain the active role of the needle in transmitting the host-cell contact signal from the tip to the base of the T3SS through conformational changes as well as during the injection of effector proteins. In this chapter, we summarize the current knowledge about the structure and the role of the T3SS needle during T3SS assembly and effector secretion.
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Affiliation(s)
- Birgit Habenstein
- University of Bordeaux, CNRS, UMR 5248, European Institute of Chemistry and Biology, 2 rue Robert Escarpit, Pessac, 33607, France.
| | - Nadia El Mammeri
- University of Bordeaux, CNRS, UMR 5248, European Institute of Chemistry and Biology, 2 rue Robert Escarpit, Pessac, 33607, France
| | - James Tolchard
- University of Bordeaux, CNRS, UMR 5248, European Institute of Chemistry and Biology, 2 rue Robert Escarpit, Pessac, 33607, France
| | - Gaëlle Lamon
- University of Bordeaux, CNRS, UMR 5248, European Institute of Chemistry and Biology, 2 rue Robert Escarpit, Pessac, 33607, France
| | - Arpita Tawani
- University of Bordeaux, CNRS, UMR 5248, European Institute of Chemistry and Biology, 2 rue Robert Escarpit, Pessac, 33607, France
| | - Mélanie Berbon
- University of Bordeaux, CNRS, UMR 5248, European Institute of Chemistry and Biology, 2 rue Robert Escarpit, Pessac, 33607, France
| | - Antoine Loquet
- University of Bordeaux, CNRS, UMR 5248, European Institute of Chemistry and Biology, 2 rue Robert Escarpit, Pessac, 33607, France.
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11
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Wagner S, Grin I, Malmsheimer S, Singh N, Torres-Vargas CE, Westerhausen S. Bacterial type III secretion systems: a complex device for the delivery of bacterial effector proteins into eukaryotic host cells. FEMS Microbiol Lett 2018; 365:5068689. [PMID: 30107569 PMCID: PMC6140923 DOI: 10.1093/femsle/fny201] [Citation(s) in RCA: 112] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Accepted: 08/08/2018] [Indexed: 12/21/2022] Open
Abstract
Virulence-associated type III secretion systems (T3SS) serve the injection of bacterial effector proteins into eukaryotic host cells. They are able to secrete a great diversity of substrate proteins in order to modulate host cell function, and have evolved to sense host cell contact and to inject their substrates through a translocon pore in the host cell membrane. T3SS substrates contain an N-terminal signal sequence and often a chaperone-binding domain for cognate T3SS chaperones. These signals guide the substrates to the machine where substrates are unfolded and handed over to the secretion channel formed by the transmembrane domains of the export apparatus components and by the needle filament. Secretion itself is driven by the proton motive force across the bacterial inner membrane. The needle filament measures 20-150 nm in length and is crowned by a needle tip that mediates host-cell sensing. Secretion through T3SS is a highly regulated process with early, intermediate and late substrates. A strict secretion hierarchy is required to build an injectisome capable of reaching, sensing and penetrating the host cell membrane, before host cell-acting effector proteins are deployed. Here, we review the recent progress on elucidating the assembly, structure and function of T3SS injectisomes.
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Affiliation(s)
- Samuel Wagner
- University of Tübingen, Interfaculty Institute of Microbiology and Infection Medicine (IMIT), Elfriede-Aulhorn-Str. 6, 72076 Tübingen, Germany
- German Center for Infection Research (DZIF), partner-site Tübingen, Elfriede-Aulhorn-Str. 6, 72076 Tübingen, Germany
| | - Iwan Grin
- University of Tübingen, Interfaculty Institute of Microbiology and Infection Medicine (IMIT), Elfriede-Aulhorn-Str. 6, 72076 Tübingen, Germany
| | - Silke Malmsheimer
- University of Tübingen, Interfaculty Institute of Microbiology and Infection Medicine (IMIT), Elfriede-Aulhorn-Str. 6, 72076 Tübingen, Germany
| | - Nidhi Singh
- University of Tübingen, Interfaculty Institute of Microbiology and Infection Medicine (IMIT), Elfriede-Aulhorn-Str. 6, 72076 Tübingen, Germany
| | - Claudia E Torres-Vargas
- University of Tübingen, Interfaculty Institute of Microbiology and Infection Medicine (IMIT), Elfriede-Aulhorn-Str. 6, 72076 Tübingen, Germany
| | - Sibel Westerhausen
- University of Tübingen, Interfaculty Institute of Microbiology and Infection Medicine (IMIT), Elfriede-Aulhorn-Str. 6, 72076 Tübingen, Germany
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12
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Souza CDA, Richards KL, Park Y, Schwartz M, Torruellas Garcia J, Schesser Bartra S, Plano GV. The YscE/YscG chaperone and YscF N-terminal sequences target YscF to the Yersinia pestis type III secretion apparatus. MICROBIOLOGY-SGM 2018; 164:338-348. [PMID: 29458689 DOI: 10.1099/mic.0.000610] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The needle structures of type III secretion (T3S) systems are formed by the secretion and polymerization of a needle subunit protein, YscF in Yersinia pestis. A subset of T3S systems employ unique heterodimeric chaperones, YscE and YscG in Y. pestis, to prevent the polymerization of needle subunits within the bacterial cell. We demonstrate that the YscE/YscG chaperone is also required for stable YscF expression and for secretion of YscF. Overexpression of a functional maltose-binding protein (MBP)-YscG hybrid protein stabilized cytoplasmic YscF but YscF was not secreted in the absence of YscE. Furthermore, a YscE mutant protein was identified that functioned with YscG to stabilize cytosolic YscF; however, YscF was not secreted. These findings confirm a role for the YscE/YscG chaperone in YscF secretion and suggest that YscE may have a specific role in this process. Recent studies have shown that YscF deleted of its N-terminal 15 residues is still secreted and functional, suggesting that YscF may not require an N-terminal secretion signal. However, we demonstrate that YscF contains an N-terminal secretion signal and that a functional N-terminal signal is required for YscF secretion.
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Affiliation(s)
| | | | - YoSon Park
- Department of Genetics, University of Pennsylvania, Perelman School of Medicine, Philadelphia, PA 19104, USA
| | - Michael Schwartz
- Department of Microbiology and Immunology, University of Miami, Miller School of Medicine, Miami, FL 33101, USA
| | - Julie Torruellas Garcia
- Department of Biological Sciences, Nova Southeastern University, Fort Lauderdale, FL 33314, USA
| | - Sara Schesser Bartra
- Department of Microbiology and Immunology, University of Miami, Miller School of Medicine, Miami, FL 33101, USA
| | - Gregory V Plano
- Department of Microbiology and Immunology, University of Miami, Miller School of Medicine, Miami, FL 33101, USA
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13
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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.
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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
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14
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Abstract
Type III secretion (T3S) systems are found in a large number of gram-negative bacteria where they function to manipulate the biology of infected hosts. Hosts targeted by T3S systems are widely distributed in nature and are represented by animals and plants. T3S systems are found in diverse genera of bacteria and they share a common core structure and function. Effector proteins are delivered by T3S systems into targeted host cells without prior secretion of the effectors into the environment. Instead, an assembled translocon structure functions to translocate effectors across eukaryotic cell membranes. In many cases, T3S systems are essential virulence factors and in some instances they promote symbiotic interactions.
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Affiliation(s)
- Danielle L Jessen Condry
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND, USA.
| | - Matthew L Nilles
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND, USA
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15
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A Method for Characterizing the Type III Secretion System's Contribution to Pathogenesis: Homologous Recombination to Generate Yersinia pestis Type III Secretion System Mutants. Methods Mol Biol 2016. [PMID: 27837489 DOI: 10.1007/978-1-4939-6649-3_13] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
The type III (T3S) secretion system of many gram-negative bacteria is a surface-exposed protein secretion apparatus used to directly inject bacterial effector molecules into eukaryotic cells. These effector molecules contribute to bacterial pathogenesis in many ways, and have been shown to be crucial for infectivity. Here, we describe a protocol for using homologous recombination to generate T3S system mutants to assess the role of different T3S system proteins in bacterial pathogenesis.
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16
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Huang YC, Lin YC, Wei CF, Deng WL, Huang HC. The pathogenicity factor HrpF interacts with HrpA and HrpG to modulate type III secretion system (T3SS) function and t3ss expression in Pseudomonas syringae pv. averrhoi. MOLECULAR PLANT PATHOLOGY 2016; 17:1080-94. [PMID: 26638129 PMCID: PMC6638529 DOI: 10.1111/mpp.12349] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2015] [Revised: 11/05/2015] [Accepted: 11/29/2015] [Indexed: 05/08/2023]
Abstract
To ensure the optimal infectivity on contact with host cells, pathogenic Pseudomonas syringae has evolved a complex mechanism to control the expression and construction of the functional type III secretion system (T3SS) that serves as a dominant pathogenicity factor. In this study, we showed that the hrpF gene of P. syringae pv. averrhoi, which is located upstream of hrpG, encodes a T3SS-dependent secreted/translocated protein. Mutation of hrpF leads to the loss of bacterial ability on elicitation of disease symptoms in the host and a hypersensitive response in non-host plants, and the secretion or translocation of the tested T3SS substrates into the bacterial milieu or plant cells. Moreover, overexpression of hrpF in the wild-type results in delayed HR and reduced t3ss expression. The results of protein-protein interactions demonstrate that HrpF interacts directly with HrpG and HrpA in vitro and in vivo, and protein stability assays reveal that HrpF assists HrpA stability in the bacterial cytoplasm, which is reduced by a single amino acid substitution at the 67th lysine residue of HrpF with alanine. Taken together, the data presented here suggest that HrpF has two roles in the assembly of a functional T3SS: one by acting as a negative regulator, possibly involved in the HrpSVG regulation circuit via binding to HrpG, and the other by stabilizing HrpA in the bacterial cytoplasm via HrpF-HrpA interaction prior to the secretion and formation of Hrp pilus on the bacterial surface.
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Affiliation(s)
- Yi-Chiao Huang
- Department of Plant Pathology, National Chung Hsing University, Taichung, 40227, Taiwan
- Graduate Institute of Biotechnology, National Chung Hsing University, Taichung, 40227, Taiwan
| | - Yuan-Chuen Lin
- Graduate Institute of Biotechnology, National Chung Hsing University, Taichung, 40227, Taiwan
| | - Chia-Fong Wei
- Graduate Institute of Biotechnology, National Chung Hsing University, Taichung, 40227, Taiwan
| | - Wen-Ling Deng
- Department of Plant Pathology, National Chung Hsing University, Taichung, 40227, Taiwan
- Agricultural Biotechnology Center, National Chung Hsing University, Taichung, 40227, Taiwan
| | - Hsiou-Chen Huang
- Graduate Institute of Biotechnology, National Chung Hsing University, Taichung, 40227, Taiwan
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17
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Structure of the Cellulose Synthase Complex of Gluconacetobacter hansenii at 23.4 Å Resolution. PLoS One 2016; 11:e0155886. [PMID: 27214134 PMCID: PMC4877109 DOI: 10.1371/journal.pone.0155886] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2016] [Accepted: 05/05/2016] [Indexed: 01/08/2023] Open
Abstract
Bacterial crystalline cellulose is used in biomedical and industrial applications, but the molecular mechanisms of synthesis are unclear. Unlike most bacteria, which make non-crystalline cellulose, Gluconacetobacter hansenii extrudes profuse amounts of crystalline cellulose. Its cellulose synthase (AcsA) exists as a complex with accessory protein AcsB, forming a 'terminal complex' (TC) that has been visualized by freeze-fracture TEM at the base of ribbons of crystalline cellulose. The catalytic AcsAB complex is embedded in the cytoplasmic membrane. The C-terminal portion of AcsC is predicted to form a translocation channel in the outer membrane, with the rest of AcsC possibly interacting with AcsD in the periplasm. It is thus believed that synthesis from an organized array of TCs coordinated with extrusion by AcsC and AcsD enable this bacterium to make crystalline cellulose. The only structural data that exist for this system are the above mentioned freeze-fracture TEM images, fluorescence microscopy images revealing that TCs align in a row, a crystal structure of AcsD bound to cellopentaose, and a crystal structure of PilZ domain of AcsA. Here we advance our understanding of the structural basis for crystalline cellulose production by bacterial cellulose synthase by determining a negative stain structure resolved to 23.4 Å for highly purified AcsAB complex that catalyzed incorporation of UDP-glucose into β-1,4-glucan chains, and responded to the presence of allosteric activator cyclic diguanylate. Although the AcsAB complex was functional in vitro, the synthesized cellulose was not visible in TEM. The negative stain structure revealed that AcsAB is very similar to that of the BcsAB synthase of Rhodobacter sphaeroides, a non-crystalline cellulose producing bacterium. The results indicate that the crystalline cellulose producing and non-crystalline cellulose producing bacteria share conserved catalytic and membrane translocation components, and support the hypothesis that it is the extrusion mechanism and order in linearly arrayed TCs that enables production of crystalline cellulose.
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18
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Edwardsiella tarda EscE (Orf13 Protein) Is a Type III Secretion System-Secreted Protein That Is Required for the Injection of Effectors, Secretion of Translocators, and Pathogenesis in Fish. Infect Immun 2015; 84:2-10. [PMID: 26459509 DOI: 10.1128/iai.00986-15] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Accepted: 10/03/2015] [Indexed: 11/20/2022] Open
Abstract
The type III secretion system (T3SS) of Edwardsiella tarda is crucial for its intracellular survival and pathogenesis in fish. The orf13 gene (escE) of E. tarda is located 84 nucleotides (nt) upstream of esrC in the T3SS gene cluster. We found that EscE is secreted and translocated in a T3SS-dependent manner and that amino acids 2 to 15 in the N terminus were required for a completely functional T3SS in E. tarda. Deletion of escE abolished the secretion of T3SS translocators, as well as the secretion and translocation of T3SS effectors, but did not influence their intracellular protein levels in E. tarda. Complementation of the escE mutant with a secretion-incompetent EscE derivative restored the secretion of translocators and effectors. Interestingly, the effectors that were secreted and translocated were positively correlated with the EscE protein level in E. tarda. The escE mutant was attenuated in the blue gourami fish infection model, as its 50% lethal dose (LD50) increased to 4 times that of the wild type. The survival rate of the escE mutant-strain-infected fish was 69%, which was much higher than that of the fish infected with the wild-type bacteria (6%). Overall, EscE represents a secreted T3SS regulator that controls effector injection and translocator secretion, thus contributing to E. tarda pathogenesis in fish. The homology of EscE within the T3SSs of other bacterial species suggests that the mechanism of secretion and translocation control used by E. tarda may be commonly used by other bacterial pathogens.
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19
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Wang R, Zhong Y, Gu X, Yuan J, Saeed AF, Wang S. The pathogenesis, detection, and prevention of Vibrio parahaemolyticus. Front Microbiol 2015; 6:144. [PMID: 25798132 PMCID: PMC4350439 DOI: 10.3389/fmicb.2015.00144] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2015] [Accepted: 02/07/2015] [Indexed: 12/02/2022] Open
Abstract
Vibrio parahaemolyticus, a Gram-negative motile bacterium that inhabits marine and estuarine environments throughout the world, is a major food-borne pathogen that causes life-threatening diseases in humans after the consumption of raw or undercooked seafood. The global occurrence of V. parahaemolyticus accentuates the importance of investigating its virulence factors and their effects on the human host. This review describes the virulence factors of V. parahaemolyticus reported to date, including hemolysin, urease, two type III secretion systems and two type VI secretion systems, which both cause both cytotoxicity in cultured cells and enterotoxicity in animal models. We describe various types of detection methods, based on virulence factors, that are used for quantitative detection of V. parahaemolyticus in seafood. We also discuss some useful preventive measures and therapeutic strategies for the diseases mediated by V. parahaemolyticus, which can reduce, to some extent, the damage to humans and aquatic animals attributable to V. parahaemolyticus. This review extends our understanding of the pathogenic mechanisms of V. parahaemolyticus mediated by virulence factors and the diseases it causes in its human host. It should provide new insights for the diagnosis, treatment, and prevention of V. parahaemolyticus infection.
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Affiliation(s)
- Rongzhi Wang
- Key Laboratory of Biopesticide and Chemical Biology of Education Ministry and Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, School of Life Sciences, Fujian Agriculture and Forestry University Fuzhou, China
| | - Yanfang Zhong
- Key Laboratory of Biopesticide and Chemical Biology of Education Ministry and Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, School of Life Sciences, Fujian Agriculture and Forestry University Fuzhou, China
| | - Xiaosong Gu
- Key Laboratory of Biopesticide and Chemical Biology of Education Ministry and Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, School of Life Sciences, Fujian Agriculture and Forestry University Fuzhou, China
| | - Jun Yuan
- Key Laboratory of Biopesticide and Chemical Biology of Education Ministry and Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, School of Life Sciences, Fujian Agriculture and Forestry University Fuzhou, China
| | - Abdullah F Saeed
- Key Laboratory of Biopesticide and Chemical Biology of Education Ministry and Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, School of Life Sciences, Fujian Agriculture and Forestry University Fuzhou, China
| | - Shihua Wang
- Key Laboratory of Biopesticide and Chemical Biology of Education Ministry and Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, School of Life Sciences, Fujian Agriculture and Forestry University Fuzhou, China
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20
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The N terminus of type III secretion needle protein YscF from Yersinia pestis functions to modulate innate immune responses. Infect Immun 2015; 83:1507-22. [PMID: 25644012 DOI: 10.1128/iai.02687-14] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The type III secretion system is employed by many pathogens, including the genera Yersinia, Shigella, Pseudomonas, and Salmonella, to deliver effector proteins into eukaryotic cells. The injectisome needle is formed by the polymerization of a single protein, e.g., YscF (Yersinia pestis), PscF (Pseudomonas aeruginosa), PrgI (Salmonella enterica SPI-1), SsaG (Salmonella enterica SPI-2), or MxiH (Shigella flexneri). In this study, we demonstrated that the N termini of some needle proteins, particularly the N terminus of YscF from Yersinia pestis, influences host immune responses. The N termini of several needle proteins were truncated and tested for the ability to induce inflammatory responses in a human monocytic cell line (THP-1 cells). Truncated needle proteins induced proinflammatory cytokines to different magnitudes than the corresponding wild-type proteins, except SsaG. Notably, N-terminally truncated YscF induced significantly higher activation of NF-κB and/or AP-1 and higher induction of proinflammatory cytokines, suggesting that a function of the N terminus of YscF is interference with host sensing of YscF, consistent with Y. pestis pathogenesis. To directly test the ability of the N terminus of YscF to suppress cytokine induction, a YscF-SsaG chimera with 15 N-terminal amino acids from YscF added to SsaG was constructed. The chimeric YscF-SsaG induced lower levels of cytokines than wild-type SsaG. However, the addition of 15 random amino acids to SsaG had no effect on NF-κB/AP-1 activation. These results suggest that the N terminus of YscF can function to decrease cytokine induction, perhaps contributing to a favorable immune environment leading to survival of Y. pestis within the eukaryotic host.
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21
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Mercante V, Duarte CM, Sánchez CM, Zalguizuri A, Caetano-Anollés G, Lepek VC. The absence of protein Y4yS affects negatively the abundance of T3SS Mesorhizobium loti secretin, RhcC2, in bacterial membranes. FRONTIERS IN PLANT SCIENCE 2015; 6:12. [PMID: 25688250 PMCID: PMC4311626 DOI: 10.3389/fpls.2015.00012] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/10/2014] [Accepted: 01/06/2015] [Indexed: 06/04/2023]
Abstract
Mesorhizobium loti MAFF303099 has a functional type III secretion system (T3SS) that is involved in the determination of nodulation competitiveness on Lotus. The M. loti T3SS cluster contains gene y4yS (mlr8765) that codes for a protein of unknown function (Y4yS). A mutation in the y4yS gene favors the M. loti symbiotic competitive ability on Lotus tenuis cv. Esmeralda and affects negatively the secretion of proteins through T3SS. Here we localize Y4yS in the bacterial membrane using a translational reporter peptide fusion. In silico analysis indicated that this protein presents a tetratricopeptide repeat (TPR) domain, a signal peptide and a canonical lipobox LGCC in the N-terminal sequence. These features that are shared with proteins required for the formation of the secretin complex in type IV secretion systems and in the Tad system, together with its localization, suggest that the y4yS-encoded protein is required for the formation of the M. loti T3SS secretin (RhcC2) complex. Remarkably, analysis of RhcC2 in the wild-type and M. loti y4yS mutant strains indicated that the absence of Y4yS affects negatively the accumulation of normal levels of RhcC2 in the membrane.
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Affiliation(s)
- Virginia Mercante
- Instituto de Investigaciones Biotecnológicas “Dr. Rodolfo A. Ugalde,” Universidad Nacional de San MartínBuenos Aires, Argentina
| | - Cecilia M. Duarte
- Instituto de Investigaciones Biotecnológicas “Dr. Rodolfo A. Ugalde,” Universidad Nacional de San MartínBuenos Aires, Argentina
| | - Cintia M. Sánchez
- Instituto de Investigaciones Biotecnológicas “Dr. Rodolfo A. Ugalde,” Universidad Nacional de San MartínBuenos Aires, Argentina
| | - Andrés Zalguizuri
- Instituto de Investigaciones Biotecnológicas “Dr. Rodolfo A. Ugalde,” Universidad Nacional de San MartínBuenos Aires, Argentina
| | - Gustavo Caetano-Anollés
- Evolutionary Bioinformatics Laboratory, Department of Crop Sciences, University of IllinoisUrbana-Champaign, USA
| | - Viviana C. Lepek
- Instituto de Investigaciones Biotecnológicas “Dr. Rodolfo A. Ugalde,” Universidad Nacional de San MartínBuenos Aires, Argentina
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22
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Dai W, Li Z. Conserved type III secretion system exerts important roles in Chlamydia trachomatis. INTERNATIONAL JOURNAL OF CLINICAL AND EXPERIMENTAL PATHOLOGY 2014; 7:5404-5414. [PMID: 25337183 PMCID: PMC4203154] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 07/31/2014] [Accepted: 08/23/2014] [Indexed: 06/04/2023]
Abstract
Upon infection, Chlamydiae alter host cellular functions in a variety of ways. Chlamydial infection prevents host cell apoptosis, induces re-organization of the actin cytoskeleton and alters host cellular signaling mechanisms. Chlamydia is among the many pathogenic Gram-negative bacteria that employ the type III secretion system (T3SS) to overcome host defenses and exploit available resources. T3SS are used by many Gram-negative bacterial pathogens to manipulate eukaryotic host cells through the delivery of effector proteins into their cytosol and membranes. T3SS is an evolutionarily refined, virulence determinant of Gram-negative bacteria where more than 20 proteins form an apparatus, generally termed injectisome, to achieve the vectorial secretion and translocation of anti-host effector proteins. This review describes challenges and recent advances that have revealed how Chlamydia trachomatis utilizes diversification to produce a conserved T3SS that exerts an important role in Chlamydia trachomatis.
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Affiliation(s)
- Wenting Dai
- Pathogenic Biology Institute, School of Medicine, University of South China Hengyang City, Hunan Province, P. R. China
| | - Zhongyu Li
- Pathogenic Biology Institute, School of Medicine, University of South China Hengyang City, Hunan Province, P. R. China
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23
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Abrusci P, McDowell MA, Lea SM, Johnson S. Building a secreting nanomachine: a structural overview of the T3SS. Curr Opin Struct Biol 2014; 25:111-7. [PMID: 24704748 PMCID: PMC4045390 DOI: 10.1016/j.sbi.2013.11.001] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2013] [Revised: 11/05/2013] [Accepted: 11/06/2013] [Indexed: 12/21/2022]
Abstract
To fulfill complex biological tasks, such as locomotion and protein translocation, bacteria assemble macromolecular nanomachines. One such nanodevice, the type III secretion system (T3SS), has evolved to provide a means of transporting proteins from the bacterial cytoplasm across the periplasmic and extracellular spaces. T3SS can be broadly classified into two highly homologous families: the flagellar T3SS which drive cell motility, and the non-flagellar T3SS (NF-T3SS) that inject effector proteins into eukaryotic host cells, a trait frequently associated with virulence. Although the structures and symmetries of ancillary components of the T3SS have diversified to match requirements of different species adapted to different niches, recent genetic, molecular and structural studies demonstrate that these systems are built by arranging homologous modular protein assemblies.
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Affiliation(s)
- Patrizia Abrusci
- Sir William Dunn School of Pathology, Oxford University, South Parks Road, Oxford OX1 3RE, United Kingdom
| | - Melanie A McDowell
- Sir William Dunn School of Pathology, Oxford University, South Parks Road, Oxford OX1 3RE, United Kingdom
| | - Susan M Lea
- Sir William Dunn School of Pathology, Oxford University, South Parks Road, Oxford OX1 3RE, United Kingdom.
| | - Steven Johnson
- Sir William Dunn School of Pathology, Oxford University, South Parks Road, Oxford OX1 3RE, United Kingdom
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24
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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.
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Affiliation(s)
- Andreas Diepold
- Department of Biochemistry, University of Oxford, Oxford, UK
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25
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Burkinshaw BJ, Strynadka NCJ. Assembly and structure of the T3SS. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1843:1649-63. [PMID: 24512838 DOI: 10.1016/j.bbamcr.2014.01.035] [Citation(s) in RCA: 94] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2013] [Revised: 01/27/2014] [Accepted: 01/29/2014] [Indexed: 02/06/2023]
Abstract
The Type III Secretion System (T3SS) is a multi-mega Dalton apparatus assembled from more than twenty components and is found in many species of animal and plant bacterial pathogens. The T3SS creates a contiguous channel through the bacterial and host membranes, allowing injection of specialized bacterial effector proteins directly to the host cell. In this review, we discuss our current understanding of T3SS assembly and structure, as well as highlight structurally characterized Salmonella effectors. This article is part of a Special Issue entitled: Protein trafficking and secretion in bacteria. Guest Editors: Anastassios Economou and Ross Dalbey.
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Affiliation(s)
- Brianne J Burkinshaw
- Department of Biochemistry and Molecular Biology, Center for Blood Research, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Natalie C J Strynadka
- Department of Biochemistry and Molecular Biology, Center for Blood Research, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada.
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26
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Mutations in the Pseudomonas aeruginosa needle protein gene pscF confer resistance to phenoxyacetamide inhibitors of the type III secretion system. Antimicrob Agents Chemother 2014; 58:2211-20. [PMID: 24468789 DOI: 10.1128/aac.02795-13] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The type III secretion system (T3SS) is a clinically important virulence mechanism in Pseudomonas aeruginosa that secretes and translocates effector toxins into host cells, impeding the host's rapid innate immune response to infection. Inhibitors of T3SS may be useful as prophylactic or adjunctive therapeutic agents to augment the activity of antibiotics in P. aeruginosa infections, such as pneumonia and bacteremia. One such inhibitor, the phenoxyacetamide MBX 1641, exhibits very responsive structure-activity relationships, including striking stereoselectivity, in its inhibition of P. aeruginosa T3SS. These features suggest interaction with a specific, but unknown, protein target. Here, we identify the apparent molecular target by isolating inhibitor-resistant mutants and mapping the mutation sites by deep sequencing. Selection and sequencing of four independent mutants resistant to the phenoxyacetamide inhibitor MBX 2359 identified the T3SS gene pscF, encoding the needle apparatus, as the only locus of mutations common to all four strains. Transfer of the wild-type and mutated alleles of pscF, together with its chaperone and cochaperone genes pscE and pscG, to a ΔpscF P. aeruginosa strain demonstrated that each of the single-codon mutations in pscF is necessary and sufficient to provide secretion and translocation that is resistant to a variety of phenoxyacetamide inhibitor analogs but not to T3SS inhibitors with different chemical scaffolds. These results implicate the PscF needle protein as an apparent new molecular target for T3SS inhibitor discovery and suggest that three other chemically distinct T3SS inhibitors interact with one or more different targets or a different region of PscF.
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Houben ENG, Korotkov KV, Bitter W. Take five - Type VII secretion systems of Mycobacteria. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2013; 1843:1707-16. [PMID: 24263244 DOI: 10.1016/j.bbamcr.2013.11.003] [Citation(s) in RCA: 140] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2013] [Revised: 11/07/2013] [Accepted: 11/09/2013] [Indexed: 11/18/2022]
Abstract
Mycobacteria use type VII secretion (T7S) systems to secrete proteins across their complex cell envelope. Pathogenic mycobacteria, such as the notorious pathogen Mycobacterium tuberculosis, have up to five of these secretion systems, named ESX-1 to ESX-5. At least three of these secretion systems are essential for mycobacterial virulence and/or viability. Elucidating T7S is therefore essential to understand the success of M. tuberculosis and other pathogenic mycobacteria as pathogens, and could be instrumental to identify novel targets for drug- and vaccine-development. Recently, significant progress has been achieved in the identification of T7S substrates and a general secretion motif. In addition, a start has been made with unraveling the mechanism of secretion and the structural analysis of the different subunits. This review summarizes these recent findings, which are incorporated in a working model of this complex machinery. This article is part of a Special Issue entitled: Protein trafficking and secretion in bacteria. Guest Editors: Anastassios Economou and Ross Dalbey.
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Affiliation(s)
- Edith N G Houben
- VU University, Amsterdam, The Netherlands; VU University Medical Center, Amsterdam, The Netherlands.
| | | | - Wilbert Bitter
- VU University, Amsterdam, The Netherlands; VU University Medical Center, Amsterdam, The Netherlands
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Abstract
Members of the order Chlamydiales comprise a group of exquisitely evolved parasites of eukaryotic hosts that extends from single-celled amoeba to mammals. The most notable are human pathogens and include the agent of oculogenital disease Chlamydia trachomatis, the respiratory pathogen C. pneumoniae, and the zoonotic agent C. psittaci. All of these species are obligate intracellular bacteria that develop within parasitophorous vesicles termed inclusions. This demanding lifestyle necessitates orchestrated entry into nonphagocytic cells, creation of a privileged intracellular niche, and subversion of potent host defenses. All chlamydial genomes contain the coding capacity for a nonflagellar type III secretion system, and this mechanism has arisen as an essential contributor to chlamydial virulence. The emergence of tractable approaches to the genetic manipulation of chlamydiae raises the possibility of explosive progress in understanding this important contributor to chlamydial pathogenesis. This minireview considers challenges and recent advances that have revealed how chlamydiae have maintained conserved aspects of T3S while exploiting diversification to yield a system that exerts a fundamental role in the unique biology of Chlamydia species.
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Generation and Characterization of a scFv Antibody Against T3SS Needle of Vibrio parahaemolyticus. Indian J Microbiol 2013; 54:143-50. [PMID: 25320414 DOI: 10.1007/s12088-013-0428-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2013] [Accepted: 09/25/2013] [Indexed: 12/31/2022] Open
Abstract
Vibrio parahaemolyticus, a halophilic gram-negative bacterium, is a food-borne pathogen that largely inhabits marine and estuarine environments, and poses a serious threat to human and animal health all over the world. The hollow "needle" channel, a specific assemble of T3SS which exists in most of gram-negative bacteria, plays a key role in the transition of virulence effectors to host cells. In this study, needle protein VP1694 was successfully expressed and purified, and the fusion protein Trx-VP1694 was used to immunize Balb/c mice. Subsequently, a phage single-chain fragment variable antibody (scFv) library was constructed, and a specific scFv against VP1694 named scFv-FA7 was screened by phage display panning. To further identify the characters of scFv, the soluble expression vector pACYC-scFv-skp was constructed and the soluble scFv was purified by Ni(2+) affinity chromatography. ELISA analysis showed that the scFv-FA7 was specific to VP1694 antigen, and its affinity constant was 1.07 × 10(8 )L/mol. These results offer a molecular basis to prevent and cure diseases by scFv, and also provide a new strategy for further research on virulence mechanism of T3SS in V. parahaemolyticus by scFv.
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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.
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Affiliation(s)
- Alejandro Peña
- Departamento de Biología Molecular, Universidad de Cantabria, UC-CSIC-SODERCAN, Santander, Spain
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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.
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Affiliation(s)
- Srirupa Chatterjee
- Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas 66045, USA
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EscE and EscG are cochaperones for the type III needle protein EscF of enteropathogenic Escherichia coli. J Bacteriol 2013; 195:2481-9. [PMID: 23524615 DOI: 10.1128/jb.00118-13] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Type III secretion systems (T3SSs) are central virulence mechanisms used by a variety of Gram-negative bacteria to inject effector proteins into host cells. The needle polymer is an essential part of the T3SS that provides the effector proteins a continuous channel into the host cytoplasm. It has been shown for a few T3SSs that two chaperones stabilize the needle protein within the bacterial cytosol to prevent its premature polymerization. In this study, we characterized the chaperones of the enteropathogenic Escherichia coli (EPEC) needle protein EscF. We found that Orf2 and Orf29, two poorly characterized proteins encoded within the EPEC locus of enterocyte effacement (LEE), function as the needle protein cochaperones. Our finding demonstrated that both Orf2 and Orf29 are essential for type III secretion (T3S). In addition, we found that Orf2 and Orf29 associate with the bacterial membrane and form a complex with EscF. Orf2 and Orf29 were also shown to disrupt the polymerization of EscF in vitro. Prediction of the tertiary structures of Orf2 and Orf29 showed high structural homology to chaperones of other T3SS needle proteins. Overall, our data suggest that Orf2 and Orf29 function as the chaperones of the needle protein, and therefore, they have been renamed EscE and EscG.
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Tomalka AG, Stopford CM, Lee PC, Rietsch A. A translocator-specific export signal establishes the translocator-effector secretion hierarchy that is important for type III secretion system function. Mol Microbiol 2012; 86:1464-81. [PMID: 23121689 DOI: 10.1111/mmi.12069] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/11/2012] [Indexed: 11/29/2022]
Abstract
Type III secretion systems are used by many Gram-negative pathogens to directly deliver effector proteins into the cytoplasm of host cells. To accomplish this, bacteria secrete translocator proteins that form a pore in the host-cell membrane through which the effector proteins are then introduced into the host cell. Evidence from multiple systems indicates that the pore-forming translocator proteins are exported before effectors, but how this secretion hierarchy is established is unclear. Here we used the Pseudomonas aeruginosa translocator protein PopD as a model to identify its export signals. The N-terminal secretion signal and chaperone, PcrH, are required for export under all conditions. Two novel signals in PopD, one proximal to the chaperone binding site and one at the very C-terminus of the protein, are required for export of PopD before effector proteins. These novel export signals establish the translocator-effector secretion hierarchy, which in turn, is critical for the delivery of effectors into host cells.
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Affiliation(s)
- Amanda G Tomalka
- Department of Molecular Biology and Microbiology, Case Western Reserve University, 10900 Euclid Ave., Cleveland, OH 44106-4960, USA
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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.
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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]
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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.
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Affiliation(s)
- Agata Kosarewicz
- Research Institute of Molecular Pathology, Dr. Bohr Gasse 7, A-1030 Vienna, Austria
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Schreiner M, Niemann HH. Crystal structure of the Yersinia enterocolitica type III secretion chaperone SycD in complex with a peptide of the minor translocator YopD. BMC STRUCTURAL BIOLOGY 2012; 12:13. [PMID: 22708907 PMCID: PMC3443056 DOI: 10.1186/1472-6807-12-13] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/08/2012] [Accepted: 06/18/2012] [Indexed: 11/23/2022]
Abstract
Background Type III secretion systems are used by Gram-negative bacteria as “macromolecular syringes” to inject effector proteins into eukaryotic cells. Two hydrophobic proteins called translocators form the necessary pore in the host cell membrane. Both translocators depend on binding to a single chaperone in the bacterial cytoplasm to ensure their stability and efficient transport through the secretion needle. It was suggested that the conserved chaperones bind the more divergent translocators via a hexapeptide motif that is found in both translocators and conserved between species. Results We crystallized a synthetic decapeptide from the Yersinia enterocolitica minor type III secretion translocator YopD bound to its cognate chaperone SycD and determined the complex structure at 2.5 Å resolution. The structure of peptide-bound SycD is almost identical to that of apo SycD with an all helical fold consisting of three tetratricopeptide repeats (TPRs) and an additional C-terminal helix. Peptide-bound SycD formed a kinked head-to-head dimer that had previously been observed for the apo form of SycD. The homodimer interface comprises both helices of the first tetratricopeptide repeat. The YopD peptide bound in extended conformation into a mainly hydrophobic groove on the concave side of SycD. TPRs 1 and 2 of SycD form three hydrophobic pockets that accommodated the conserved hydrophobic residues at position 1, 3 and 6 of the translocator hexapeptide sequence. Two tyrosines that are highly conserved among translocator chaperones contribute to the hydrophobic patches but also form hydrogen bonds to the peptide backbone. Conclusions The interaction between SycD and YopD is very similar to the binding of the Pseudomonas minor translocator PopD to its chaperone PcrH and the Shigella major translocator IpaB to its chaperone IpgC. This confirms the prediction made by Kolbe and co-workers that a hexapeptide with hydrophobic residues at three positions is a conserved chaperone binding motif. Because the hydrophobic groove on the concave side of translocator chaperones is involved in binding of the major and the minor translocator, simultaneous binding of both translocators to a single type III secretion class II chaperone appears unlikely.
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Affiliation(s)
- Madeleine Schreiner
- Department of Chemistry, Bielefeld University, PO Box 10 01 31, 33501 Bielefeld, Germany
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Structure of a type III secretion needle at 7-Å resolution provides insights into its assembly and signaling mechanisms. Proc Natl Acad Sci U S A 2012; 109:4461-6. [PMID: 22388746 DOI: 10.1073/pnas.1116126109] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Type III secretion systems of Gram-negative bacteria form injection devices that deliver effector proteins into eukaryotic cells during infection. They span both bacterial membranes and the extracellular space to connect with the host cell plasma membrane. Their extracellular portion is a needle-like, hollow tube that serves as a secretion conduit for effector proteins. The needle of Shigella flexneri is approximately 50-nm long and 7-nm thick and is made by the helical assembly of one protein, MxiH. We provide a 7-Å resolution 3D image reconstruction of the Shigella needle by electron cryomicroscopy, which resolves α-helices and a β-hairpin that has never been observed in the crystal and solution structures of needle proteins, including MxiH. An atomic model of the needle based on the 3D-density map, in comparison with that of the bacterial-flagellar filament, provides insights into how such a thin tubular structure is stably assembled by intricate intermolecular interactions. The map also illuminates how the needle-length control protein functions as a ruler within the central channel during export of MxiH for assembly at the distal end of the needle, and how the secretion-activation signal may be transduced through a conformational change of the needle upon host-cell contact.
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Barta ML, Dickenson NE, Patil M, Keightley A, Wyckoff GJ, Picking WD, Picking WL, Geisbrecht BV. The structures of coiled-coil domains from type III secretion system translocators reveal homology to pore-forming toxins. J Mol Biol 2012; 417:395-405. [PMID: 22321794 DOI: 10.1016/j.jmb.2012.01.026] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2011] [Revised: 01/03/2012] [Accepted: 01/11/2012] [Indexed: 11/25/2022]
Abstract
Many pathogenic Gram-negative bacteria utilize type III secretion systems (T3SSs) to alter the normal functions of target cells. Shigella flexneri uses its T3SS to invade human intestinal cells to cause bacillary dysentery (shigellosis) that is responsible for over one million deaths per year. The Shigella type III secretion apparatus is composed of a basal body spanning both bacterial membranes and an exposed oligomeric needle. Host altering effectors are secreted through this energized unidirectional conduit to promote bacterial invasion. The active needle tip complex of S. flexneri is composed of a tip protein, IpaD, and two pore-forming translocators, IpaB and IpaC. While the atomic structure of IpaD has been elucidated and studied, structural data on the hydrophobic translocators from the T3SS family remain elusive. We present here the crystal structures of a protease-stable fragment identified within the N-terminal regions of IpaB from S. flexneri and SipB from Salmonella enterica serovar Typhimurium determined at 2.1 Å and 2.8 Å limiting resolution, respectively. These newly identified domains are composed of extended-length (114 Å in IpaB and 71 Å in SipB) coiled-coil motifs that display a high degree of structural homology to one another despite the fact that they share only 21% sequence identity. Further structural comparisons also reveal substantial similarity to the coiled-coil regions of pore-forming proteins from other Gram-negative pathogens, notably, colicin Ia. This suggests that these mechanistically separate and functionally distinct membrane-targeting proteins may have diverged from a common ancestor during the course of pathogen-specific evolutionary events.
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Affiliation(s)
- Michael L Barta
- School of Biological Sciences, University of Missouri-Kansas City, Kansas City, MO 64110, USA
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Izoré T, Job V, Dessen A. Biogenesis, regulation, and targeting of the type III secretion system. Structure 2011; 19:603-12. [PMID: 21565695 DOI: 10.1016/j.str.2011.03.015] [Citation(s) in RCA: 98] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2011] [Revised: 03/28/2011] [Accepted: 03/29/2011] [Indexed: 01/21/2023]
Abstract
The type III secretion system (T3SS) is employed by a number of Gram-negative bacterial pathogens to inject toxins into eukaryotic cells. The biogenesis of this complex machinery requires the regulated interaction between over 20 cytosolic, periplasmic, and membrane-imbedded proteins, many of which undergo processes such as polymerization, partner recognition, and partial unfolding. Elements of this intricate macromolecular system have been characterized through electron microscopy, crystallography, and NMR techniques, allowing for an initial understanding of the spatiotemporal regulation of T3SS-related events. Here, we report recent advances in the structural characterization of T3SS proteins from a number of bacteria, and provide an overview of recently identified small molecule T3SS inhibitors that could potentially be explored for novel antibacterial development.
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Affiliation(s)
- Thierry Izoré
- Bacterial Pathogenesis Group, Institut de Biologie Structurale, Université Grenoble I, 38027 Grenoble, France
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Crystal structure of the heteromolecular chaperone, AscE-AscG, from the type III secretion system in Aeromonas hydrophila. PLoS One 2011; 6:e19208. [PMID: 21559439 PMCID: PMC3084799 DOI: 10.1371/journal.pone.0019208] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2011] [Accepted: 03/22/2011] [Indexed: 12/27/2022] Open
Abstract
Background The putative needle complex subunit AscF forms a ternary complex with the chaperones AscE and AscG in the type III secretion system of Aeromonas hydrophila so as to avoid premature assembly. Previously, we demonstrated that the C-terminal region of AscG (residues 62–116) in the hetero-molecular chaperone, AscE-AscG, is disordered and susceptible to limited protease digestion. Methodology/Principal Findings Here, we report the crystal structure of the ordered AscG1–61 region in complex with AscE at 2.4 Å resolution. Helices α2 and α3 of AscE in the AscE-AscG1–61 complex assumes a helix-turn-helix conformation in an anti-parallel fashion similar to that in apo AscE. However, in the presence of AscG, an additional N-terminal helix α1 in AscE (residues 4–12) is observed. PscG or YscG in the crystal structures of PscE-PscF-PscG or YscE-YscF-YscG, respectively, assumes a typical tetratricopeptide repeat (TPR) fold with three TPR repeats and one C-terminal capping helix. By comparison, AscG in AscE-AscG1–61 comprises three anti-parallel helices that resembles the N-terminal TPR repeats in the corresponding region of PscG or YscG in PscE-PscF-PscG or YscE-YscF-YscG. Thermal denaturation of AscE-AscG and AscE-AscG1–61 complexes demonstrates that the C-terminal disordered region does not contribute to the thermal stability of the overall complex. Conclusion/Significance The N-terminal region of the AscG in the AscE-AscG complex is ordered and assumes a structure similar to those in the corresponding regions of PscE-PscG-PscF or YscE-YscF-YscG complexes. While the C-terminal region of AscG in the AscE-AscG complex is disordered and will assume its structure only in the presence of the substrate AscF. We hypothesize that AscE act as a chaperone of the chaperone to keep AscG in a stable but partially disordered state for interaction with AscF.
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Paul L, Patrick S, Nord CE, Abratt V. The role of Bacteroides fragilis RecQ DNA helicases in cell survival after metronidazole exposure. FEMS Microbiol Lett 2011; 319:125-32. [DOI: 10.1111/j.1574-6968.2011.02271.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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Matteï PJ, Faudry E, Job V, Izoré T, Attree I, Dessen A. Membrane targeting and pore formation by the type III secretion system translocon. FEBS J 2010; 278:414-26. [PMID: 21182592 DOI: 10.1111/j.1742-4658.2010.07974.x] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The type III secretion system (T3SS) is a complex macromolecular machinery employed by a number of Gram-negative species to initiate infection. Toxins secreted through the system are synthesized in the bacterial cytoplasm and utilize the T3SS to pass through both bacterial membranes and the periplasm, thus being introduced directly into the eukaryotic cytoplasm. A key element of the T3SS of all bacterial pathogens is the translocon, which comprises a pore that is inserted into the membrane of the target cell, allowing toxin injection. Three macromolecular partners associate to form the translocon: two are hydrophobic and one is hydrophilic, and the latter also associates with the T3SS needle. In this review, we discuss recent advances on the biochemical and structural characterization of the proteins involved in translocon formation, as well as their participation in the modification of intracellular signalling pathways upon infection. Models of translocon assembly and regulation are also discussed.
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Affiliation(s)
- Pierre-Jean Matteï
- Bacterial Pathogenesis Group, Institut de Biologie Structurale, UMR 5075 (CNRS/CEA/UJF), Grenoble, France
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Gendrin C, Sarrazin S, Bonnaffé D, Jault JM, Lortat-Jacob H, Dessen A. Hijacking of the pleiotropic cytokine interferon-γ by the type III secretion system of Yersinia pestis. PLoS One 2010; 5:e15242. [PMID: 21179438 PMCID: PMC3001473 DOI: 10.1371/journal.pone.0015242] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2010] [Accepted: 11/02/2010] [Indexed: 11/19/2022] Open
Abstract
Yersinia pestis, the causative agent of bubonic plague, employs its type III secretion system to inject toxins into target cells, a crucial step in infection establishment. LcrV is an essential component of the T3SS of Yersinia spp, and is able to associate at the tip of the secretion needle and take part in the translocation of anti-host effector proteins into the eukaryotic cell cytoplasm. Upon cell contact, LcrV is also released into the surrounding medium where it has been shown to block the normal inflammatory response, although details of this mechanism have remained elusive. In this work, we reveal a key aspect of the immunomodulatory function of LcrV by showing that it interacts directly and with nanomolar affinity with the inflammatory cytokine IFNγ. In addition, we generate specific IFNγ mutants that show decreased interaction capabilities towards LcrV, enabling us to map the interaction region to two basic C-terminal clusters of IFNγ. Lastly, we show that the LcrV-IFNγ interaction can be disrupted by a number of inhibitors, some of which display nanomolar affinity. This study thus not only identifies novel potential inhibitors that could be developed for the control of Yersinia-induced infection, but also highlights the diversity of the strategies used by Y. pestis to evade the immune system, with the hijacking of pleiotropic cytokines being a long-range mechanism that potentially plays a key role in the severity of plague.
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Affiliation(s)
- Claire Gendrin
- Institut de Biologie Structurale, UMR 5075 (Comissariat à l'Enérgie Atomique/Centre National de la Recherche Scientifique/Université Grenoble I), Grenoble, France
| | - Stéphane Sarrazin
- Institut de Biologie Structurale, UMR 5075 (Comissariat à l'Enérgie Atomique/Centre National de la Recherche Scientifique/Université Grenoble I), Grenoble, France
| | - David Bonnaffé
- Laboratoire de Chimie Organique Multifonctionnelle, Institut de Chimie Moléculaire et des Matériaux d'Orsay, UMR 8182, Université Paris-Sud 11, Orsay, France
| | - Jean-Michel Jault
- Institut de Biologie Structurale, UMR 5075 (Comissariat à l'Enérgie Atomique/Centre National de la Recherche Scientifique/Université Grenoble I), Grenoble, France
| | - Hugues Lortat-Jacob
- Institut de Biologie Structurale, UMR 5075 (Comissariat à l'Enérgie Atomique/Centre National de la Recherche Scientifique/Université Grenoble I), Grenoble, France
| | - Andréa Dessen
- Institut de Biologie Structurale, UMR 5075 (Comissariat à l'Enérgie Atomique/Centre National de la Recherche Scientifique/Université Grenoble I), Grenoble, France
- * E-mail:
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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.
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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
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46
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Lam WWL, Woo EJ, Kotaka M, Tam WK, Leung YC, Ling TKW, Au SWN. Molecular interaction of flagellar export chaperone FliS and cochaperone HP1076 in Helicobacter pylori. FASEB J 2010; 24:4020-32. [PMID: 20581225 DOI: 10.1096/fj.10-155242] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Flagellar export chaperone FliS prevents premature polymerization of flagellins and is critical for flagellar assembly and bacterial colonization. Previously, a yeast 2-hybrid study identified various FliS-associated proteins in Helicobacter pylori, but the implications of these interactions are not known. Here we demonstrate the biophysical interaction of FliS (HP0753) and the uncharacterized protein HP1076 from H. pylori. HP1076 possesses a cochaperone activity that promotes the folding and chaperone activity of FliS. We further determined the crystal structures of FliS, HP1076, and the binary complex at 2.7, 1.8, and 2.7 Å resolution, respectively. HP1076 adopts a helix-rich bundle structure and interestingly shares a similar fold with a flagellin homologue, hook-associated protein, and FliS. The FliS-HP1076 complex revealed an extensive electrostatic and hydrophobic binding interface, which is distinct from the flagellin binding pocket in FliS. The helical stacking interaction between HP1076 and FliS suggests that HP1076 stabilizes 2 α helices of FliS and therefore the overall structure of the bundle. Our findings provide new insights into flagellar export chaperones and may have implications for other secretion chaperones in the type III secretion system.
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Affiliation(s)
- Wendy Wai Ling Lam
- Centre of Protein Science and Crystallography, Department of Biochemistry, Faculty of Science, The Chinese University of Hong Kong, Hong Kong, China
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47
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Protein refolding is required for assembly of the type three secretion needle. Nat Struct Mol Biol 2010; 17:788-92. [PMID: 20543831 DOI: 10.1038/nsmb.1822] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2009] [Accepted: 04/01/2010] [Indexed: 12/30/2022]
Abstract
Pathogenic Gram-negative bacteria use a type three secretion system (TTSS) to deliver virulence factors into host cells. Although the order in which proteins incorporate into the growing TTSS is well described, the underlying assembly mechanisms are still unclear. Here we show that the TTSS needle protomer refolds spontaneously to extend the needle from the distal end. We developed a functional mutant of the needle protomer from Shigella flexneri and Salmonella typhimurium to study its assembly in vitro. We show that the protomer partially refolds from alpha-helix into beta-strand conformation to form the TTSS needle. Reconstitution experiments show that needle growth does not require ATP. Thus, like the structurally related flagellar systems, the needle elongates by subunit polymerization at the distal end but requires protomer refolding. Our studies provide a starting point to understand the molecular assembly mechanisms and the structure of the TTSS at atomic level.
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48
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Cochaperone interactions in export of the type III needle component PscF of Pseudomonas aeruginosa. J Bacteriol 2010; 192:3801-8. [PMID: 20494986 DOI: 10.1128/jb.00117-10] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Type III secretion (T3S) systems allow the export and translocation of bacterial effectors into the host cell cytoplasm. Secretion is accomplished by an 80-nm-long needle-like structure composed, in Pseudomonas aeruginosa, of the polymerized form of a 7-kDa protein, PscF. Two proteins, PscG and PscE, stabilize PscF within the bacterial cell before its export and polymerization. In this work we screened the 1,320-A(2) interface between the two chaperones, PscE and PscG, by site-directed mutagenesis and determined hot spot regions that are important for T3S function in vivo and complex formation in vitro. Three amino acids in PscE and five amino acids in PscG, found to be relevant for complex formation, map to the central part of the interacting surface. Stability assays on selected mutants performed both in vitro on purified PscE-PscG complexes and in vivo on P. aeruginosa revealed that PscE is a cochaperone that is essential for the stability of the main chaperone, PscG. Notably, when overexpressed from a bicistronic construct, PscG and PscF compensate for the absence of PscE in cytotoxic P. aeruginosa. These results show that all of the information needed for needle protein stabilization and folding, its presentation to the T3 secreton, and its export is present within the sequence of the PscG chaperone.
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49
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Keiski CL, Harwich M, Jain S, Neculai AM, Yip P, Robinson H, Whitney JC, Riley L, Burrows LL, Ohman DE, Howell PL. AlgK is a TPR-containing protein and the periplasmic component of a novel exopolysaccharide secretin. Structure 2010; 18:265-73. [PMID: 20159471 DOI: 10.1016/j.str.2009.11.015] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2009] [Revised: 11/19/2009] [Accepted: 11/24/2009] [Indexed: 11/28/2022]
Abstract
The opportunistic pathogen Pseudomonas aeruginosa causes chronic biofilm infections in cystic fibrosis patients. During colonization of the lung, P. aeruginosa converts to a mucoid phenotype characterized by overproduction of the exopolysaccharide alginate. Here we show that AlgK, a protein essential for production of high molecular weight alginate, is an outer membrane lipoprotein that contributes to the correct localization of the porin AlgE. Our 2.5 A structure shows AlgK is composed of 9.5 tetratricopeptide-like repeats, and three putative sites of protein-protein interaction have been identified. Bioinformatics analysis suggests that BcsA, PgaA, and PelB, involved in the production and export of cellulose, poly-beta-1,6-N-Acetyl-D-glucosamine, and Pel exopolysaccharide, respectively, share the same topology as AlgK/E. Together, our data suggest that AlgK plays a role in the assembly of the alginate biosynthetic complex and represents the periplasmic component of a new type of outer membrane secretin that differs from canonical bacterial capsular polysaccharide secretion systems.
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Affiliation(s)
- Carrie-Lynn Keiski
- Molecular Structure and Function, Hospital for Sick Children, Toronto, ON M5G 1X8, Canada
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Structural insight into the regulatory mechanisms of interactions of the flagellar type III chaperone FliT with its binding partners. Proc Natl Acad Sci U S A 2010; 107:8812-7. [PMID: 20421493 DOI: 10.1073/pnas.1001866107] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
For self-assembly of the bacterial flagellum, most of the flagellar component proteins synthesized in the cytoplasm are exported by the flagellar type III export apparatus to the growing, distal end. Flagellar protein export is highly organized and well controlled in every step of the flagellar assembly process. Flagellar-specific chaperones not only facilitate the export of their cognate proteins, as well as prevent their premature aggregation in the cytoplasm, but also play a role in fine-tuning flagellar gene expression to be coupled with the flagellar assembly process. FliT is a flagellar-specific chaperone responsible for the export of the filament-capping protein FliD and for negative control of flagellar gene expression by binding to the FlhDC complex. Here we report the crystal structure of Salmonella FliT at 3.2-A resolution. The structural and biochemical analyses clearly reveal that the C-terminal segment of FliT regulates its interactions with the FlhDC complex, FliI ATPase, and FliJ (subunits of the export apparatus), and that its conformational change is responsible for the switch in its binding partners during flagellar protein export.
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