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Oka GU, Souza DP, Sgro GG, Guzzo CR, Dunger G, Farah CS. Xanthomonas immunity proteins protect against the cis-toxic effects of their cognate T4SS effectors. EMBO Rep 2024; 25:1436-1452. [PMID: 38332152 PMCID: PMC10933484 DOI: 10.1038/s44319-024-00060-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2023] [Revised: 12/22/2023] [Accepted: 01/08/2024] [Indexed: 02/10/2024] Open
Abstract
Many bacteria kill rival species by translocating toxic effectors into target cells. Effectors are often encoded along with cognate immunity proteins that could (i) protect against "friendly-fire" (trans-intoxication) from neighboring sister cells and/or (ii) protect against internal cis-intoxication (suicide). Here, we distinguish between these two mechanisms in the case of the bactericidal Xanthomonas citri Type IV Secretion System (X-T4SS). We use a set of X. citri mutants lacking multiple effector/immunity protein (X-Tfe/X-Tfi) pairs to show that X-Tfis are not absolutely required to protect against trans-intoxication by wild-type cells. Our investigation then focused on the in vivo function of the lysozyme-like effector X-TfeXAC2609 and its cognate immunity protein X-TfiXAC2610. In the absence of X-TfiXAC2610, we observe X-TfeXAC2609-dependent and X-T4SS-independent accumulation of damage in the X. citri cell envelope, cell death, and inhibition of biofilm formation. While immunity proteins in other systems have been shown to protect against attacks by sister cells (trans-intoxication), this is an example of an antibacterial secretion system in which the immunity proteins are dedicated to protecting cells against cis-intoxication.
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Affiliation(s)
- Gabriel U Oka
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, SP, Brazil
- Structure and Function of Bacterial Nanomachines, Institut Européen de Chimie et Biologie-CNRS, UMR 5234 Microbiologie Fondamentale et Pathogénicité University of Bordeaux, Pessac, France
| | - Diorge P Souza
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, SP, Brazil
- Division of Cell Biology, MRC Laboratory of Molecular Biology, Cambridge, UK
| | - Germán G Sgro
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, SP, Brazil
- Departamento de Ciências BioMoleculares, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil
| | - Cristiane R Guzzo
- Departamento de Microbiologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, SP, Brazil
| | - German Dunger
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, SP, Brazil
- Instituto de Ciencias Agropecuarias del Litoral (ICiAgro Litoral), Universidad Nacional del Litoral, CONICET, Facultad de Ciencias Agrarias, Esperanza, Argentina
| | - Chuck S Farah
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, SP, Brazil.
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2
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Trotta KL, Hayes BM, Schneider JP, Wang J, Todor H, Rockefeller Grimes P, Zhao Z, Hatleberg WL, Silvis MR, Kim R, Koo BM, Basler M, Chou S. Lipopolysaccharide transport regulates bacterial sensitivity to a cell wall-degrading intermicrobial toxin. PLoS Pathog 2023; 19:e1011454. [PMID: 37363922 PMCID: PMC10328246 DOI: 10.1371/journal.ppat.1011454] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2023] [Revised: 07/07/2023] [Accepted: 06/01/2023] [Indexed: 06/28/2023] Open
Abstract
Gram-negative bacteria can antagonize neighboring microbes using a type VI secretion system (T6SS) to deliver toxins that target different essential cellular features. Despite the conserved nature of these targets, T6SS potency can vary across recipient species. To understand the functional basis of intrinsic T6SS susceptibility, we screened for essential Escherichia coli (Eco) genes that affect its survival when antagonized by a cell wall-degrading T6SS toxin from Pseudomonas aeruginosa, Tae1. We revealed genes associated with both the cell wall and a separate layer of the cell envelope, lipopolysaccharide, that modulate Tae1 toxicity in vivo. Disruption of genes in early lipopolysaccharide biosynthesis provided Eco with novel resistance to Tae1, despite significant cell wall degradation. These data suggest that Tae1 toxicity is determined not only by direct substrate damage, but also by indirect cell envelope homeostasis activities. We also found that Tae1-resistant Eco exhibited reduced cell wall synthesis and overall slowed growth, suggesting that reactive cell envelope maintenance pathways could promote, not prevent, self-lysis. Together, our study reveals the complex functional underpinnings of susceptibility to Tae1 and T6SS which regulate the impact of toxin-substrate interactions in vivo.
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Affiliation(s)
- Kristine L. Trotta
- Department of Biochemistry & Biophysics, University of California–San Francisco, San Francisco, California, United States of America
| | - Beth M. Hayes
- Department of Biochemistry & Biophysics, University of California–San Francisco, San Francisco, California, United States of America
| | | | - Jing Wang
- Biozentrum, University of Basel, Basel, Switzerland
| | - Horia Todor
- Department of Cell and Tissue Biology, University of California–San Francisco, San Francisco, California, United States of America
| | - Patrick Rockefeller Grimes
- Department of Biochemistry & Biophysics, University of California–San Francisco, San Francisco, California, United States of America
| | - Ziyi Zhao
- Department of Biochemistry & Biophysics, University of California–San Francisco, San Francisco, California, United States of America
| | | | - Melanie R. Silvis
- Department of Cell and Tissue Biology, University of California–San Francisco, San Francisco, California, United States of America
| | - Rachel Kim
- Department of Biochemistry & Biophysics, University of California–San Francisco, San Francisco, California, United States of America
| | - Byoung Mo Koo
- Department of Cell and Tissue Biology, University of California–San Francisco, San Francisco, California, United States of America
| | - Marek Basler
- Biozentrum, University of Basel, Basel, Switzerland
| | - Seemay Chou
- Department of Biochemistry & Biophysics, University of California–San Francisco, San Francisco, California, United States of America
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3
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Griffin ME, Klupt S, Espinosa J, Hang HC. Peptidoglycan NlpC/P60 peptidases in bacterial physiology and host interactions. Cell Chem Biol 2023; 30:436-456. [PMID: 36417916 PMCID: PMC10192474 DOI: 10.1016/j.chembiol.2022.11.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Revised: 09/15/2022] [Accepted: 10/31/2022] [Indexed: 11/23/2022]
Abstract
The bacterial cell wall is composed of a highly crosslinked matrix of glycopeptide polymers known as peptidoglycan that dictates bacterial cell morphology and protects against environmental stresses. Regulation of peptidoglycan turnover is therefore crucial for bacterial survival and growth and is mediated by key protein complexes and enzyme families. Here, we review the prevalence, structure, and activity of NlpC/P60 peptidases, a family of peptidoglycan hydrolases that are crucial for cell wall turnover and division as well as interactions with antibiotics and different hosts. Understanding the molecular functions of NlpC/P60 peptidases should provide important insight into bacterial physiology, their interactions with different kingdoms of life, and the development of new therapeutic approaches.
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Affiliation(s)
- Matthew E Griffin
- Department of Immunology and Microbiology, Scripps Research, La Jolla, CA 92037, USA
| | - Steven Klupt
- Department of Immunology and Microbiology, Scripps Research, La Jolla, CA 92037, USA
| | - Juliel Espinosa
- Laboratory of Chemical Biology and Microbial Pathogenesis, The Rockefeller University, New York, NY 10065, USA
| | - Howard C Hang
- Department of Immunology and Microbiology, Scripps Research, La Jolla, CA 92037, USA; Department of Chemistry, Scripps Research, La Jolla, CA 92037, USA.
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4
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Ozhelvaci F, Steczkiewicz K. Identification and Classification of Papain-like Cysteine Proteinases. J Biol Chem 2023:104801. [PMID: 37164157 DOI: 10.1016/j.jbc.2023.104801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2023] [Revised: 04/11/2023] [Accepted: 05/05/2023] [Indexed: 05/12/2023] Open
Abstract
Papain-like cysteine peptidases form a big and highly diverse superfamily of proteins involved in many important biological functions, such as protein turnover, deubiquitination, tissue remodeling, blood clotting, virulence, defense, and cell wall remodeling. High sequence and structure diversity observed within these proteins hinders their comprehensive classification as well as the identification of new representatives. Moreover, in general protein databases, many families already classified as papain-like lack details regarding their mechanism of action or biological function. Here, we use transitive remote homology searches and 3D modeling to newly classify 21 families to the papain-like cysteine peptidase superfamily. We attempt to predict their biological function, and provide structural chacterization of 89 protein clusters defined based on sequence similarity altogether spanning 106 papain-like families. Moreover, we systematically discuss observed diversity in sequences, structures, and catalytic sites. Eventually, we expand the list of human papain-related proteins by seven representatives, including dopamine receptor-interacting protein (DRIP1) as potential deubiquitinase, and centriole duplication regulating CEP76 as retaining catalytically active peptidase-like domain. The presented results not only provide structure-based rationales to already existing peptidase databases but also may inspire further experimental research focused on peptidase-related biological processes.
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Affiliation(s)
- Fatih Ozhelvaci
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland
| | - Kamil Steczkiewicz
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland
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5
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Trotta KL, Hayes BM, Schneider JP, Wang J, Todor H, Grimes PR, Zhao Z, Hatleberg WL, Silvis MR, Kim R, Koo BM, Basler M, Chou S. Lipopolysaccharide integrity primes bacterial sensitivity to a cell wall-degrading intermicrobial toxin. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.20.524922. [PMID: 36747731 PMCID: PMC9900751 DOI: 10.1101/2023.01.20.524922] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Gram-negative bacteria can antagonize neighboring microbes using a type VI secretion system (T6SS) to deliver toxins that target different essential cellular features. Despite the conserved nature of these targets, T6SS potency can vary across recipient species. To understand the molecular basis of intrinsic T6SS susceptibility, we screened for essential Escherichia coli genes that affect its survival when antagonized by a cell wall-degrading T6SS toxin from Pseudomonas aeruginosa , Tae1. We revealed genes associated with both the cell wall and a separate layer of the cell envelope, surface lipopolysaccharide, that modulate Tae1 toxicity in vivo . Disruption of lipopolysaccharide synthesis provided Escherichia coli (Eco) with novel resistance to Tae1, despite significant cell wall degradation. These data suggest that Tae1 toxicity is determined not only by direct substrate damage, but also by indirect cell envelope homeostasis activities. We also found that Tae1-resistant Eco exhibited reduced cell wall synthesis and overall slowed growth, suggesting that reactive cell envelope maintenance pathways could promote, not prevent, self-lysis. Together, our study highlights the consequences of co-regulating essential pathways on recipient fitness during interbacterial competition, and how antibacterial toxins leverage cellular vulnerabilities that are both direct and indirect to their specific targets in vivo .
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Affiliation(s)
- Kristine L Trotta
- Department of Biochemistry & Biophysics, University of California – San Francisco, San Francisco, CA, USA
| | - Beth M Hayes
- Department of Biochemistry & Biophysics, University of California – San Francisco, San Francisco, CA, USA
| | - Johannes P Schneider
- Focal Area Infection Biology, Biozentrum, University of Basel, Klingelbergstrasse 50/70, CH - 4056 Basel, Switzerland
| | - Jing Wang
- Focal Area Infection Biology, Biozentrum, University of Basel, Klingelbergstrasse 50/70, CH - 4056 Basel, Switzerland
| | - Horia Todor
- Department of Cell and Tissue Biology, University of California – San Francisco, San Francisco, CA, USA
| | - Patrick Rockefeller Grimes
- Department of Biochemistry & Biophysics, University of California – San Francisco, San Francisco, CA, USA
| | - Ziyi Zhao
- Department of Biochemistry & Biophysics, University of California – San Francisco, San Francisco, CA, USA
| | | | - Melanie R Silvis
- Department of Cell and Tissue Biology, University of California – San Francisco, San Francisco, CA, USA
| | - Rachel Kim
- Department of Biochemistry & Biophysics, University of California – San Francisco, San Francisco, CA, USA
| | - Byoung Mo Koo
- Department of Cell and Tissue Biology, University of California – San Francisco, San Francisco, CA, USA
| | - Marek Basler
- Focal Area Infection Biology, Biozentrum, University of Basel, Klingelbergstrasse 50/70, CH - 4056 Basel, Switzerland
| | - Seemay Chou
- Department of Biochemistry & Biophysics, University of California – San Francisco, San Francisco, CA, USA
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6
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Qin S, Xiao W, Zhou C, Pu Q, Deng X, Lan L, Liang H, Song X, Wu M. Pseudomonas aeruginosa: pathogenesis, virulence factors, antibiotic resistance, interaction with host, technology advances and emerging therapeutics. Signal Transduct Target Ther 2022; 7:199. [PMID: 35752612 PMCID: PMC9233671 DOI: 10.1038/s41392-022-01056-1] [Citation(s) in RCA: 313] [Impact Index Per Article: 156.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Revised: 06/04/2022] [Accepted: 06/08/2022] [Indexed: 02/05/2023] Open
Abstract
Pseudomonas aeruginosa (P. aeruginosa) is a Gram-negative opportunistic pathogen that infects patients with cystic fibrosis, burn wounds, immunodeficiency, chronic obstructive pulmonary disorder (COPD), cancer, and severe infection requiring ventilation, such as COVID-19. P. aeruginosa is also a widely-used model bacterium for all biological areas. In addition to continued, intense efforts in understanding bacterial pathogenesis of P. aeruginosa including virulence factors (LPS, quorum sensing, two-component systems, 6 type secretion systems, outer membrane vesicles (OMVs), CRISPR-Cas and their regulation), rapid progress has been made in further studying host-pathogen interaction, particularly host immune networks involving autophagy, inflammasome, non-coding RNAs, cGAS, etc. Furthermore, numerous technologic advances, such as bioinformatics, metabolomics, scRNA-seq, nanoparticles, drug screening, and phage therapy, have been used to improve our understanding of P. aeruginosa pathogenesis and host defense. Nevertheless, much remains to be uncovered about interactions between P. aeruginosa and host immune responses, including mechanisms of drug resistance by known or unannotated bacterial virulence factors as well as mammalian cell signaling pathways. The widespread use of antibiotics and the slow development of effective antimicrobials present daunting challenges and necessitate new theoretical and practical platforms to screen and develop mechanism-tested novel drugs to treat intractable infections, especially those caused by multi-drug resistance strains. Benefited from has advancing in research tools and technology, dissecting this pathogen's feature has entered into molecular and mechanistic details as well as dynamic and holistic views. Herein, we comprehensively review the progress and discuss the current status of P. aeruginosa biophysical traits, behaviors, virulence factors, invasive regulators, and host defense patterns against its infection, which point out new directions for future investigation and add to the design of novel and/or alternative therapeutics to combat this clinically significant pathogen.
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Affiliation(s)
- Shugang Qin
- Department of Critical Care Medicine, Frontiers Science Center for Disease-related Molecular Network, State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University, Chengdu, China
| | - Wen Xiao
- Department of Critical Care Medicine, Frontiers Science Center for Disease-related Molecular Network, State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University, Chengdu, China
| | - Chuanmin Zhou
- State Key Laboratory of Virology, School of Public Health, Wuhan University, Wuhan, 430071, P.R. China
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND, 58203, USA
| | - Qinqin Pu
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND, 58203, USA
| | - Xin Deng
- Department of Biomedical Sciences, City University of Hong Kong, Hong Kong, People's Republic of China
| | - Lefu Lan
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
| | - Haihua Liang
- College of Life Sciences, Northwest University, Xi'an, ShaanXi, 710069, China
| | - Xiangrong Song
- Department of Critical Care Medicine, Frontiers Science Center for Disease-related Molecular Network, State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University, Chengdu, China.
| | - Min Wu
- Department of Critical Care Medicine, Frontiers Science Center for Disease-related Molecular Network, State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University, Chengdu, China.
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND, 58203, USA.
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7
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Formylglycine-generating enzyme-like proteins constitute a novel family of widespread type VI secretion system immunity proteins. J Bacteriol 2021; 203:e0028121. [PMID: 34398661 DOI: 10.1128/jb.00281-21] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Competition is a critical aspect of bacterial life, as it enables niche establishment and facilitates the acquisition of essential nutrients. Warfare between Gram-negative bacteria is largely mediated by the type VI secretion system (T6SS), a dynamic nanoweapon that delivers toxic effector proteins from an attacking cell to adjacent bacteria in a contact-dependent manner. Effector-encoding bacteria prevent self-intoxication and kin cell killing by the expression of immunity proteins, which prevent effector toxicity by specifically binding their cognate effector and either occluding its active site or preventing structural rearrangements necessary for effector activation. In this study, we investigate Tsi3, a previously uncharacterized T6SS immunity protein present in multiple strains of the human pathogen Acinetobacter baumannii. We show that Tsi3 is the cognate immunity protein of the antibacterial effector of unknown function Tse3. Our bioinformatic analyses indicate that Tsi3 homologs are widespread among Gram-negative bacteria, often encoded within T6SS effector-immunity modules. Surprisingly, we found that Tsi3 homologs are predicted to possess a characteristic formylglycine-generating enzyme (FGE) domain, which is present in various enzymatic proteins. Our data shows that Tsi3-mediated immunity is dependent on Tse3-Tsi3 protein-protein interactions and that Tsi3 homologs from various bacteria do not provide immunity against non-kin Tse3. Thus, we conclude that Tsi3 homologs are unlikely to be functional enzymes. Collectively, our work identifies FGE domain-containing proteins as important mediators of immunity against T6SS attacks and indicates that the FGE domain can be co-opted as a scaffold in multiple proteins to carry out diverse functions. Importance Despite the wealth of knowledge on the diversity of biochemical activities carried out by T6SS effectors, comparably little is known about the various strategies bacteria employ to prevent susceptibility to T6SS-dependent bacterial killing. Our work establishes a novel family of T6SS immunity proteins with a characteristic FGE domain. This domain is present in enzymatic proteins with various catalytic activities. Our characterization of Tsi3 expands the known functions carried out by FGE-like proteins to include defense during T6SS-mediated bacterial warfare. Moreover, it highlights the evolution of FGE domain-containing proteins to carry out diverse biological functions.
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8
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Yadav SK, Magotra A, Ghosh S, Krishnan A, Pradhan A, Kumar R, Das J, Sharma M, Jha G. Immunity proteins of dual nuclease T6SS effectors function as transcriptional repressors. EMBO Rep 2021; 22:e51857. [PMID: 33786997 PMCID: PMC8183406 DOI: 10.15252/embr.202051857] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Revised: 02/26/2021] [Accepted: 03/08/2021] [Indexed: 12/31/2022] Open
Abstract
Bacteria utilize type VI secretion system (T6SS) to deliver antibacterial toxins to target co-habiting bacteria. Here, we report that Burkholderia gladioli strain NGJ1 deploys certain T6SS effectors (TseTBg), having both DNase and RNase activities to kill target bacteria. RNase activity is prominent on NGJ1 as well as other bacterial RNA while DNase activity is pertinent to only other bacteria. The associated immunity (TsiTBg) proteins harbor non-canonical helix-turn-helix motifs and demonstrate transcriptional repression activity, similar to the antitoxins of type II toxin-antitoxin (TA) systems. Genome analysis reveals that homologs of TseTBg are either encoded as TA or T6SS effectors in diverse bacteria. Our results indicate that a new ORF (encoding a hypothetical protein) has evolved as a result of operonic fusion of TA type TseTBg homolog with certain T6SS-related genes by the action of IS3 transposable elements. This has potentially led to the conversion of a TA into T6SS effector in Burkholderia. Our study exemplifies that bacteria can recruit toxins of TA systems as T6SS weapons to diversify its arsenal to dominate during inter-bacterial competitions.
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Affiliation(s)
- Sunil Kumar Yadav
- Plant Microbe Interactions LaboratoryNational Institute of Plant Genome ResearchAruna Asaf Ali MargIndia
| | - Ankita Magotra
- Plant Microbe Interactions LaboratoryNational Institute of Plant Genome ResearchAruna Asaf Ali MargIndia
| | - Srayan Ghosh
- Plant Microbe Interactions LaboratoryNational Institute of Plant Genome ResearchAruna Asaf Ali MargIndia
| | - Aiswarya Krishnan
- Plant Microbe Interactions LaboratoryNational Institute of Plant Genome ResearchAruna Asaf Ali MargIndia
| | - Amrita Pradhan
- Plant Microbe Interactions LaboratoryNational Institute of Plant Genome ResearchAruna Asaf Ali MargIndia
| | - Rahul Kumar
- Plant Microbe Interactions LaboratoryNational Institute of Plant Genome ResearchAruna Asaf Ali MargIndia
| | - Joyati Das
- Plant Microbe Interactions LaboratoryNational Institute of Plant Genome ResearchAruna Asaf Ali MargIndia
| | - Mamta Sharma
- Plant Microbe Interactions LaboratoryNational Institute of Plant Genome ResearchAruna Asaf Ali MargIndia
| | - Gopaljee Jha
- Plant Microbe Interactions LaboratoryNational Institute of Plant Genome ResearchAruna Asaf Ali MargIndia
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9
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Jurėnas D, Journet L. Activity, delivery, and diversity of Type VI secretion effectors. Mol Microbiol 2020; 115:383-394. [PMID: 33217073 DOI: 10.1111/mmi.14648] [Citation(s) in RCA: 71] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Revised: 11/10/2020] [Accepted: 11/13/2020] [Indexed: 12/28/2022]
Abstract
The bacterial type VI secretion system (T6SS) system is a contractile secretion apparatus that delivers proteins to neighboring bacterial or eukaryotic cells. Antibacterial effectors are mostly toxins that inhibit the growth of other species and help to dominate the niche. A broad variety of these toxins cause cell lysis of the prey cell by disrupting the cell envelope. Other effectors are delivered into the cytoplasm where they affect DNA integrity, cell division or exhaust energy resources. The modular nature of T6SS machinery allows different means of recruitment of toxic effectors to secreted inner tube and spike components that act as carriers. Toxic effectors can be translationally fused to the secreted components or interact with them through specialized structural domains. These interactions can also be assisted by dedicated chaperone proteins. Moreover, conserved sequence motifs in effector-associated domains are subject to genetic rearrangements and therefore engage in the diversification of the arsenal of toxic effectors. This review discusses the diversity of T6SS secreted toxins and presents current knowledge about their loading on the T6SS machinery.
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Affiliation(s)
- Dukas Jurėnas
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires, Institut de Microbiologie de la Méditerranée, Aix-Marseille Université-CNRS, UMR 7255, Marseille, France
| | - Laure Journet
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires, Institut de Microbiologie de la Méditerranée, Aix-Marseille Université-CNRS, UMR 7255, Marseille, France
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10
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Wettstadt S, Filloux A. Manipulating the type VI secretion system spike to shuttle passenger proteins. PLoS One 2020; 15:e0228941. [PMID: 32101557 PMCID: PMC7043769 DOI: 10.1371/journal.pone.0228941] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Accepted: 01/27/2020] [Indexed: 12/21/2022] Open
Abstract
The type VI secretion system (T6SS) is a contractile injection apparatus that translocates a spike loaded with various effectors directly into eukaryotic or prokaryotic target cells. Pseudomonas aeruginosa can load either one of its three T6SSs with a variety of toxic bullets using different but specific modes. The T6SS spike, which punctures the bacterial cell envelope allowing effector transport, consists of a torch-like VgrG trimer on which sits a PAAR protein sharpening the VgrG tip. VgrG itself sits on the Hcp tube and all elements, packed into a T6SS sheath, are propelled out of the cell and into target cells. On occasion, effectors are covalent extensions of VgrG, PAAR or Hcp proteins, which are then coined "evolved" components as opposed to canonical. Here, we show how various passenger domains could be fused to the C terminus of a canonical VgrG, VgrG1a from P. aeruginosa, and be sent into the bacterial culture supernatant. There is no restriction on the passenger type, although the efficacy may vary greatly, since we used either an unrelated T6SS protein, β-lactamase, a covalent extension of an "evolved" VgrG, VgrG2b, or a Hcp-dependent T6SS toxin, Tse2. Our data further highlights an exceptional modularity/flexibility for loading the T6SS nano-weapon. Refining the parameters to optimize delivery of passenger proteins of interest would have attractive medical and industrial applications. This may for example involve engineering the T6SS as a delivery system to shuttle toxins into either bacterial pathogens or tumour cells which would be an original approach in the fight against antimicrobial resistant bacteria or cancer.
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Affiliation(s)
- Sarah Wettstadt
- MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Alain Filloux
- MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Imperial College London, London, United Kingdom
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11
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Effector⁻Immunity Pairs Provide the T6SS Nanomachine its Offensive and Defensive Capabilities. Molecules 2018; 23:molecules23051009. [PMID: 29701633 PMCID: PMC6099711 DOI: 10.3390/molecules23051009] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Revised: 04/13/2018] [Accepted: 04/23/2018] [Indexed: 01/23/2023] Open
Abstract
Type VI protein secretion systems (T6SSs) are specialized transport apparatus which can target both eukaryotic and prokaryotic cells and play key roles in host⁻pathogen⁻microbiota interactions. Therefore, T6SSs have attracted much attention as a research topic during the past ten years. In this review, we particularly summarized the T6SS antibacterial function, which involves an interesting offensive and defensive mechanism of the effector⁻immunity (E⁻I) pairs. The three main categories of effectors that target the cell wall, membranes, and nucleic acids during bacterial interaction, along with their corresponding immunity proteins are presented. We also discuss structural analyses of several effectors and E⁻I pairs, which explain the offensive and defensive mechanisms underpinning T6SS function during bacterial competition for niche-space, as well as the bioinformatics, proteomics, and protein⁻protein interaction (PPI) methods used to identify and characterize T6SS mediated E⁻I pairs. Additionally, we described PPI methods for verifying E⁻I pairs.
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12
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Ge X, Wei W, Li G, Sun M, Li H, Wu J, Hu F. Isolated Pseudomonas aeruginosa strain VIH2 and antagonistic properties against Ralstonia solanacearum. Microb Pathog 2017; 111:519-526. [PMID: 28847494 DOI: 10.1016/j.micpath.2017.08.020] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2017] [Revised: 08/10/2017] [Accepted: 08/16/2017] [Indexed: 11/29/2022]
Abstract
The aim of this study was to isolates with antagonist activity against R. solanacearum. Thirty-two bacterial isolates were obtained from samples, and they were screened for potential antagonistic activity against R. Solanacearum. Using the agar spot method, ten out of the 21 tested bacteria showed antilisterial activity. VIH2 had the highest inhibitory effect on the growth of R. Solanacearum. Based on 16S rDNA and Biolog test analysis, the strain VIH2 was identified as Pseudomonas aeruginosa. Single-factor and Response Surface Methodology experiments were used to optimize the culture medium and conditions. This study was to explore whether the hemolysin-co-regulated protein secretion island I (HSI-I)-encoded type VI secretion system (T6SS) in Pseudomonas can be used as a biological control approach against Ralstonia solanacearum under field conditions. Bacterial competition assay showed that the HSI-I type T6SS of strain VIH2 exhibited dramatic antibacterial killing activity against R. solanacearum. The HSI-I T6SS of P. aeruginosa was regulated by the ppKA gene. We disrupted the gene ppKA in VIH2 by a single crossover to yield the VIH2 (ΔppKA) mutant. The antagonism of VIH2 was significantly decreased by ppKA gene disruption. In conclusion, our data supported the idea that HSI-I T6SS plays a crucial role in the antagonistic action of strain VIH2 against R. solanacearum. This alternative approach for antagonism against R. solanacearum might help develop attenuated strains of engineered bacteria for biological control.
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Affiliation(s)
- Xincheng Ge
- Soil Ecology Lab, College of Resources and Environmental Sciences, Nanjing Agricultural University, No. 6 TongWei Road, Nanjing 210095, Jiangsu Province, People's Republic of China
| | - Wei Wei
- Soil Ecology Lab, College of Resources and Environmental Sciences, Nanjing Agricultural University, No. 6 TongWei Road, Nanjing 210095, Jiangsu Province, People's Republic of China
| | - Gen Li
- Soil Ecology Lab, College of Resources and Environmental Sciences, Nanjing Agricultural University, No. 6 TongWei Road, Nanjing 210095, Jiangsu Province, People's Republic of China
| | - Mingming Sun
- Soil Ecology Lab, College of Resources and Environmental Sciences, Nanjing Agricultural University, No. 6 TongWei Road, Nanjing 210095, Jiangsu Province, People's Republic of China
| | - Huixin Li
- Soil Ecology Lab, College of Resources and Environmental Sciences, Nanjing Agricultural University, No. 6 TongWei Road, Nanjing 210095, Jiangsu Province, People's Republic of China
| | - Jun Wu
- Soil Ecology Lab, College of Resources and Environmental Sciences, Nanjing Agricultural University, No. 6 TongWei Road, Nanjing 210095, Jiangsu Province, People's Republic of China.
| | - Feng Hu
- Soil Ecology Lab, College of Resources and Environmental Sciences, Nanjing Agricultural University, No. 6 TongWei Road, Nanjing 210095, Jiangsu Province, People's Republic of China.
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13
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Abstract
Bacterial type VI secretion systems (T6SSs) function as contractile nanomachines to puncture target cells and deliver lethal effectors. In the 10 years since the discovery of the T6SS, much has been learned about the structure and function of this versatile protein secretion apparatus. Most of the conserved protein components that comprise the T6SS apparatus itself have been identified and ascribed specific functions. In addition, numerous effector proteins that are translocated by the T6SS have been identified and characterized. These protein effectors usually represent toxic cargoes that are delivered by the attacker cell to a target cell. Researchers in the field are beginning to better understand the lifestyle or physiology that dictates when bacteria normally express their T6SS. In this article, we consider what is known about the structure and regulation of the T6SS, the numerous classes of antibacterial effector T6SS substrates, and how the action of the T6SS relates to a given lifestyle or behavior in certain bacteria.
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14
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Yang XY, Li ZQ, She Z, Geng Z, Xu JH, Gao ZQ, Dong YH. Structural analysis of Pseudomonas aeruginosa H3-T6SS immunity proteins. FEBS Lett 2016; 590:2787-96. [PMID: 27397502 DOI: 10.1002/1873-3468.12291] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2016] [Revised: 05/31/2016] [Accepted: 06/27/2016] [Indexed: 01/13/2023]
Abstract
The Pseudomonas aeruginosa PldB protein is a transkingdom effector secreted by the Type VI Secretion System (T6SS). PA5088, PA5087, and PA5086 are three immunity proteins that can suppress the virulence of PldB. We report the crystal structures of PA5088 and PA5087 at 2.0 and 2.1 Å resolution, respectively. PA5088 and PA5087 both consist of several Sel1-like Repeats (SLRs) and form super-ring folds. Our structural analysis of these proteins revealed key differences among PA5088, PA5087, and their homologs. Our docking experiments have shed light on the putative interaction mechanism of their function as phospholipase D inhibitors.
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Affiliation(s)
- Xiao-Yun Yang
- School of Life Sciences, University of Science and Technology of China, Hefei, China
| | - Zong-Qiang Li
- College of Life Science and Technology, Huazhong Agriculture University, Wuhan, China
| | - Zhun She
- Multidiscipline Research Center, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, China
| | - Zhi Geng
- Multidiscipline Research Center, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, China
| | - Jian-Hua Xu
- Multidiscipline Research Center, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, China
| | - Zeng-Qiang Gao
- Multidiscipline Research Center, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, China
| | - Yu-Hui Dong
- Multidiscipline Research Center, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, China
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15
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Flaugnatti N, Le TTH, Canaan S, Aschtgen MS, Nguyen VS, Blangy S, Kellenberger C, Roussel A, Cambillau C, Cascales E, Journet L. A phospholipase A1
antibacterial Type VI secretion effector interacts directly with the C-terminal domain of the VgrG spike protein for delivery. Mol Microbiol 2016; 99:1099-118. [DOI: 10.1111/mmi.13292] [Citation(s) in RCA: 110] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/26/2015] [Indexed: 12/19/2022]
Affiliation(s)
- Nicolas Flaugnatti
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires, CNRS - Aix-Marseille Université, UMR 7255, Institut de Microbiologie de la Méditerranée; 31 Chemin Joseph Aiguier, 13402 Marseille Cedex 20 France
| | - Thi Thu Hang Le
- Architecture et Fonction des Macromolécules Biologiques, CNRS - UMR 7257, Campus de Luminy, Case 932; 13288 Marseille Cedex 09 France
- Architecture et Fonction des Macromolécules Biologiques, Aix-Marseille Université, Campus de Luminy, Case 932; 13288 Marseille Cedex 09 France
| | - Stéphane Canaan
- Laboratoire d'Enzymologie Interfaciale et de Physiologie de la Lipolyse, CNRS - Aix-Marseille Université, UMR 7282; 31 Chemin Joseph Aiguier, 13402 Marseille Cedex 20 France
| | - Marie-Stéphanie Aschtgen
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires, CNRS - Aix-Marseille Université, UMR 7255, Institut de Microbiologie de la Méditerranée; 31 Chemin Joseph Aiguier, 13402 Marseille Cedex 20 France
| | - Van Son Nguyen
- Architecture et Fonction des Macromolécules Biologiques, CNRS - UMR 7257, Campus de Luminy, Case 932; 13288 Marseille Cedex 09 France
- Architecture et Fonction des Macromolécules Biologiques, Aix-Marseille Université, Campus de Luminy, Case 932; 13288 Marseille Cedex 09 France
| | - Stéphanie Blangy
- Architecture et Fonction des Macromolécules Biologiques, CNRS - UMR 7257, Campus de Luminy, Case 932; 13288 Marseille Cedex 09 France
- Architecture et Fonction des Macromolécules Biologiques, Aix-Marseille Université, Campus de Luminy, Case 932; 13288 Marseille Cedex 09 France
| | - Christine Kellenberger
- Architecture et Fonction des Macromolécules Biologiques, CNRS - UMR 7257, Campus de Luminy, Case 932; 13288 Marseille Cedex 09 France
- Architecture et Fonction des Macromolécules Biologiques, Aix-Marseille Université, Campus de Luminy, Case 932; 13288 Marseille Cedex 09 France
| | - Alain Roussel
- Architecture et Fonction des Macromolécules Biologiques, CNRS - UMR 7257, Campus de Luminy, Case 932; 13288 Marseille Cedex 09 France
- Architecture et Fonction des Macromolécules Biologiques, Aix-Marseille Université, Campus de Luminy, Case 932; 13288 Marseille Cedex 09 France
| | - Christian Cambillau
- Architecture et Fonction des Macromolécules Biologiques, CNRS - UMR 7257, Campus de Luminy, Case 932; 13288 Marseille Cedex 09 France
- Architecture et Fonction des Macromolécules Biologiques, Aix-Marseille Université, Campus de Luminy, Case 932; 13288 Marseille Cedex 09 France
| | - Eric Cascales
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires, CNRS - Aix-Marseille Université, UMR 7255, Institut de Microbiologie de la Méditerranée; 31 Chemin Joseph Aiguier, 13402 Marseille Cedex 20 France
| | - Laure Journet
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires, CNRS - Aix-Marseille Université, UMR 7255, Institut de Microbiologie de la Méditerranée; 31 Chemin Joseph Aiguier, 13402 Marseille Cedex 20 France
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16
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Alcoforado Diniz J, Liu YC, Coulthurst SJ. Molecular weaponry: diverse effectors delivered by the Type VI secretion system. Cell Microbiol 2015; 17:1742-51. [PMID: 26432982 PMCID: PMC4832377 DOI: 10.1111/cmi.12532] [Citation(s) in RCA: 114] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2015] [Revised: 09/22/2015] [Accepted: 09/25/2015] [Indexed: 12/18/2022]
Abstract
The Type VI secretion system is a widespread bacterial nanomachine, used to deliver toxins directly into eukaryotic or prokaryotic target cells. These secreted toxins, or effectors, act on diverse cellular targets, and their action provides the attacking bacterial cell with a significant fitness advantage, either against rival bacteria or eukaryotic host organisms. In this review, we discuss the delivery of diverse effectors by the Type VI secretion system, the modes of action of the so-called 'anti-bacterial' and 'anti-eukaryotic' effectors, the mechanism of self-resistance against anti-bacterial effectors and the evolutionary implications of horizontal transfer of Type VI secretion system-associated toxins. Whilst it is likely that many more effectors remain to be identified, it is already clear that toxins delivered by this secretion system represent efficient weapons against both bacteria and eukaryotes.
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Affiliation(s)
- Juliana Alcoforado Diniz
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dundee, DD1 5EH, UK
| | - Yi-Chia Liu
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dundee, DD1 5EH, UK
| | - Sarah J Coulthurst
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dundee, DD1 5EH, UK
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17
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Bacterial killing via a type IV secretion system. Nat Commun 2015; 6:6453. [PMID: 25743609 DOI: 10.1038/ncomms7453] [Citation(s) in RCA: 160] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2014] [Accepted: 01/29/2015] [Indexed: 12/24/2022] Open
Abstract
Type IV secretion systems (T4SSs) are multiprotein complexes that transport effector proteins and protein-DNA complexes through bacterial membranes to the extracellular milieu or directly into the cytoplasm of other cells. Many bacteria of the family Xanthomonadaceae, which occupy diverse environmental niches, carry a T4SS with unknown function but with several characteristics that distinguishes it from other T4SSs. Here we show that the Xanthomonas citri T4SS provides these cells the capacity to kill other Gram-negative bacterial species in a contact-dependent manner. The secretion of one type IV bacterial effector protein is shown to require a conserved C-terminal domain and its bacteriolytic activity is neutralized by a cognate immunity protein whose 3D structure is similar to peptidoglycan hydrolase inhibitors. This is the first demonstration of the involvement of a T4SS in bacterial killing and points to this special class of T4SS as a mediator of both antagonistic and cooperative interbacterial interactions.
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18
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Chen L, Zou Y, She P, Wu Y. Composition, function, and regulation of T6SS in Pseudomonas aeruginosa. Microbiol Res 2015; 172:19-25. [PMID: 25721475 DOI: 10.1016/j.micres.2015.01.004] [Citation(s) in RCA: 102] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2014] [Revised: 01/03/2015] [Accepted: 01/03/2015] [Indexed: 11/17/2022]
Abstract
Bacterial cells can communicate with their surrounding environment through secretion systems. Type VI secretion system (T6SS) is one of the most recently discovered secretion systems, which is distributed widely in Gram-negative bacteria such as Pseudomonas aeruginosa (P. aeruginosa), an important opportunistic pathogen. This protein secretion system shares similarity with the puncturing device of bacteriophages in structure. P. aeruginosa is an important opportunistic pathogen and distributes widely in diverse environment. T6SS is beneficial to survival advantage of P. aeruginosa by delivering toxins to its neighboring pathogens and translocating protein effectors into the host cells. T6SS is also the virulence factor and takes part in biofilm formation of P. aeruginosa. The functions of T6SS in P. aeruginosa are regulated at transcriptional, posttranscriptional and posttranslational levels by diverse mechanisms. This article reviews the latest progress in the structure, effector proteins, biological function, and regulation mechanisms of P. aeruginosa T6SS.
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Affiliation(s)
- Lihua Chen
- Department of Medicine Clinical Laboratory, The Third Xiangya Hospital of Central South University, Changsha 410013, Hunan, PR China
| | - Yaru Zou
- Department of Medicine Clinical Laboratory, The Third Xiangya Hospital of Central South University, Changsha 410013, Hunan, PR China
| | - Pengfei She
- Department of Medicine Clinical Laboratory, The Third Xiangya Hospital of Central South University, Changsha 410013, Hunan, PR China
| | - Yong Wu
- Department of Medicine Clinical Laboratory, The Third Xiangya Hospital of Central South University, Changsha 410013, Hunan, PR China.
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19
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Lu D, Zheng Y, Liao N, Wei L, Xu B, Liu X, Liu J. The structural basis of the Tle4–Tli4 complex reveals the self-protection mechanism of H2-T6SS inPseudomonas aeruginosa. ACTA ACUST UNITED AC 2014; 70:3233-43. [DOI: 10.1107/s1399004714023967] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2014] [Accepted: 10/30/2014] [Indexed: 01/02/2023]
Abstract
The type VI secretion system (T6SS) has recently been demonstrated to mediate interbacterial competition and to discriminate between self and nonself. T6SS+bacteria employ toxic effectors to inhibit rival cells and concurrently use effector cognate immunity proteins to protect their sibling cells. The effector and immunity pairs (E–I pairs) endow the bacteria with a great advantage in niche competition. Tle4–Tli4 (PA1510–PA1509) is a newly identified E–I pair that is controlled by H2-T6SS inPseudomonas aeruginosa. Tle4 exhibits phospholipase activity, which destroys the cell membrane of rival cells, and the periplasm-located Tli4 in donor cells eliminates this toxic effect of Tle4. In this paper, the structure of the Tle4–Tli4 complex is reported at 1.75 Å resolution. Tle4 consists of two domains: a conserved α/β-hydrolase domain and an unusual cap domain in which two lid regions (lid1 and lid2) display a closed conformation that buries the catalytic triad in a deep funnel. Tli4 also displays a two-domain structure, in which a large lobe and a small lobe form a crab claw-like conformation. Tli4 uses this crab claw to grasp the cap domain of Tle4, especially the lid2 region, which prevents the interfacial activation of Tle4 and thus causes enzymatic dysfunction of Tle4 in sister cells.
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20
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Durand E, Cambillau C, Cascales E, Journet L. VgrG, Tae, Tle, and beyond: the versatile arsenal of Type VI secretion effectors. Trends Microbiol 2014; 22:498-507. [DOI: 10.1016/j.tim.2014.06.004] [Citation(s) in RCA: 156] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Revised: 06/16/2014] [Accepted: 06/18/2014] [Indexed: 12/20/2022]
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21
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Hu H, Zhang H, Gao Z, Wang D, Liu G, Xu J, Lan K, Dong Y. Structure of the type VI secretion phospholipase effector Tle1 provides insight into its hydrolysis and membrane targeting. ACTA ACUST UNITED AC 2014; 70:2175-85. [DOI: 10.1107/s1399004714012899] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2014] [Accepted: 06/03/2014] [Indexed: 08/30/2023]
Abstract
A diverse superfamily of phospholipases consisting of the type VI lipase effectors Tle1–Tle5 secreted by the bacterial type VI secretion system (T6SS) have recently been identified as antibacterial effectors that hydrolyze membrane phospholipids. These effectors show no significant homology to known lipases, and their mechanism of membrane targeting and hydrolysis of phospholipids remains unknown. Here, the crystal structure of Tle1 (∼96.5 kDa) fromPseudomonas aeruginosarefined to 2.0 Å resolution is reported, representing the first structure of this superfamily. Its overall structure can be divided into two distinct parts, the phospholipase catalytic module and the putative membrane-anchoring module; this arrangement has not previously been observed in known lipase structures. The phospholipase catalytic module has a canonical α/β-hydrolase fold and mutation of any residue in the Ser-Asp-His catalytic triad abolishes its toxicity. The putative membrane-anchoring module adopts an open conformation composed of three amphipathic domains, and its partial folds are similar to those of several periplasmic or membrane proteins. A cell-toxicity assay revealed that the putative membrane-anchoring module is critical to Tle1 antibacterial activity. A molecular-dynamics (MD) simulation system in which the putative membrane-anchoring module embedded into a bilayer was stable over 50 ns. These structure–function studies provide insight into the hydrolysis and membrane-targeting process of the unique phospholipase Tle1.
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22
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Ghequire MGK, De Mot R. Ribosomally encoded antibacterial proteins and peptides from Pseudomonas. FEMS Microbiol Rev 2014; 38:523-68. [PMID: 24923764 DOI: 10.1111/1574-6976.12079] [Citation(s) in RCA: 139] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Revised: 05/05/2014] [Accepted: 05/16/2014] [Indexed: 12/26/2022] Open
Abstract
Members of the Pseudomonas genus produce diverse secondary metabolites affecting other bacteria, fungi or predating nematodes and protozoa but are also equipped with the capacity to secrete different types of ribosomally encoded toxic peptides and proteins, ranging from small microcins to large tailocins. Studies with the human pathogen Pseudomonas aeruginosa have revealed that effector proteins of type VI secretion systems are part of the antibacterial armamentarium deployed by pseudomonads. A novel class of antibacterial proteins with structural similarity to plant lectins was discovered by studying antagonism among plant-associated Pseudomonas strains. A genomic perspective on pseudomonad bacteriocinogeny shows that the modular architecture of S pyocins of P. aeruginosa is retained in a large diversified group of bacteriocins, most of which target DNA or RNA. Similar modularity is present in as yet poorly characterized Rhs (recombination hot spot) proteins and CDI (contact-dependent inhibition) proteins. Well-delimited domains for receptor recognition or cytotoxicity enable the design of chimeric toxins with novel functionalities, which has been applied successfully for S and R pyocins. Little is known regarding how these antibacterials are released and ultimately reach their targets. Other remaining issues concern the identification of environmental triggers activating these systems and assessment of their ecological impact in niches populated by pseudomonads.
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23
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Lu D, Shang G, Zhang H, Yu Q, Cong X, Yuan J, He F, Zhu C, Zhao Y, Yin K, Chen Y, Hu J, Zhang X, Yuan Z, Xu S, Hu W, Cang H, Gu L. Structural insights into the T6SS effector protein Tse3 and the Tse3-Tsi3 complex fromPseudomonas aeruginosareveal a calcium-dependent membrane-binding mechanism. Mol Microbiol 2014; 92:1092-112. [DOI: 10.1111/mmi.12616] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/10/2014] [Indexed: 12/22/2022]
Affiliation(s)
- Defen Lu
- State Key Laboratory of Microbial Technology; Shandong University; Jinan 250100 Shandong China
- The Liver Centre of Fujian Province; MengChao Hepatobiliary Hospital of Fujian Medical University; Fuzhou 350025 Fujian China
| | - Guijun Shang
- State Key Laboratory of Microbial Technology; Shandong University; Jinan 250100 Shandong China
| | - Heqiao Zhang
- Institute of Biophysics; Chinese Academy of Sciences; Beijing 100101 China
- School of Life Sciences; Tsinghua University; Beijing 100084 China
| | - Qian Yu
- State Key Laboratory of Microbial Technology; Shandong University; Jinan 250100 Shandong China
| | - Xiaoyan Cong
- State Key Laboratory of Microbial Technology; Shandong University; Jinan 250100 Shandong China
| | - Jupeng Yuan
- Institute of Medical Genetics; Shandong University School of Medicine; Jinan 250012 Shandong China
| | - Fengjuan He
- Institute of Medical Genetics; Shandong University School of Medicine; Jinan 250012 Shandong China
| | - Chunyuan Zhu
- State Key Laboratory of Microbial Technology; Shandong University; Jinan 250100 Shandong China
| | - Yanyu Zhao
- State Key Laboratory of Microbial Technology; Shandong University; Jinan 250100 Shandong China
| | - Kun Yin
- State Key Laboratory of Microbial Technology; Shandong University; Jinan 250100 Shandong China
| | - Yuanyuan Chen
- Institute of Biophysics; Chinese Academy of Sciences; Beijing 100101 China
| | - Junqiang Hu
- State Key Laboratory of Microbial Technology; Shandong University; Jinan 250100 Shandong China
| | - Xiaodan Zhang
- State Key Laboratory of Microbial Technology; Shandong University; Jinan 250100 Shandong China
| | - Zenglin Yuan
- State Key Laboratory of Microbial Technology; Shandong University; Jinan 250100 Shandong China
| | - Sujuan Xu
- State Key Laboratory of Microbial Technology; Shandong University; Jinan 250100 Shandong China
| | - Wei Hu
- State Key Laboratory of Microbial Technology; Shandong University; Jinan 250100 Shandong China
| | - Huaixing Cang
- Institute of Biophysics; Chinese Academy of Sciences; Beijing 100101 China
| | - Lichuan Gu
- State Key Laboratory of Microbial Technology; Shandong University; Jinan 250100 Shandong China
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24
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Zhang J, Zhang H, Gao Z, Hu H, Dong C, Dong YH. Structural basis for recognition of the type VI spike protein VgrG3 by a cognate immunity protein. FEBS Lett 2014; 588:1891-8. [PMID: 24751834 DOI: 10.1016/j.febslet.2014.04.016] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Revised: 04/09/2014] [Accepted: 04/09/2014] [Indexed: 10/25/2022]
Abstract
The bacterial type VI secretion system (T6SS) is used by donor cells to inject toxic effectors into receptor cells. The donor cells produce the corresponding immunity proteins to protect themselves against the effector proteins, thereby preventing their self-intoxication. Recently, the C-terminal domain of VgrG3 was identified as a T6SS effector. Information on the molecular mechanism of VgrG3 and its immunity protein TsaB has been lacking. Here, we determined the crystal structures of native TsaB and the VgrG3C-TsaB complex. VgrG3C adopts a canonical phage-T4-lysozyme-like fold. TsaB interacts with VgrG3C through molecular mimicry, and inserts into the VgrG3C pocket.
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Affiliation(s)
- Jiulong Zhang
- Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, People's Republic of China; School of Life Sciences, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230027, People's Republic of China
| | - Heng Zhang
- State Key Laboratory of Protein and Plant Gene Research, and Biodynamic Optical Imaging Center (BIOPIC), School of Life Sciences, Peking University, No. 5 Yiheyuan Road, Beijing 100871, People's Republic of China
| | - Zengqiang Gao
- Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, People's Republic of China
| | - Haidai Hu
- Key Laboratory of Molecular Virology and Immunology, Institute Pasteur of Shanghai, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, People's Republic of China
| | - Cheng Dong
- Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, People's Republic of China; State Key Laboratory of Medicinal Chemical Biology, Nankai University, Tianjin 300071, People's Republic of China.
| | - Yu-Hui Dong
- Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, People's Republic of China.
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25
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Douzi B, Spinelli S, Blangy S, Roussel A, Durand E, Brunet YR, Cascales E, Cambillau C. Crystal structure and self-interaction of the type VI secretion tail-tube protein from enteroaggregative Escherichia coli. PLoS One 2014; 9:e86918. [PMID: 24551044 PMCID: PMC3925092 DOI: 10.1371/journal.pone.0086918] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2013] [Accepted: 12/15/2013] [Indexed: 11/29/2022] Open
Abstract
The type VI secretion system (T6SS) is a widespread machine used by bacteria to control their environment and kill or disable bacterial species or eukaryotes through toxin injection. The T6SS comprises a central tube formed of stacked hexamers of hemolysin co-regulated proteins (Hcp) and terminated by a trimeric valine-glycine repeat protein G (VgrG) component, the cell puncturing device. A contractile tail sheath, formed by the TssB and TssC proteins, surrounds this tube. This syringe-like machine has been compared to an inverted phage, as both Hcp and VgrG share structural homology with tail components of Caudovirales. Here we solved the crystal structure of a tryptophan-substituted double mutant of Hcp1 from enteroaggregative Escherichia coli and compared it to the structures of other Hcps. Interestingly, we observed that the purified Hcp native protein is unable to form tubes in vitro. To better understand the rationale for observation, we measured the affinity of Hcp1 hexamers with themselves by surface plasmon resonance. The intra-hexamer interaction is weak, with a KD value of 7.2 µM. However, by engineering double cysteine mutants at defined positions, tubes of Hcp1 gathering up to 15 stacked hexamers formed in oxidative conditions. These results, together with those available in the literature regarding TssB and TssC, suggest that assembly of the T6SS tube differs significantly from that of Sipho- or Myoviridae.
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Affiliation(s)
- Badreddine Douzi
- Aix-Marseille Université, Architecture et Fonction des Macromolécules Biologiques, UMR 7257, Campus de Luminy, Case 932, Marseille, France
- Centre National de la Recherche Scientifique, Architecture et Fonction des Macromolécules Biologiques, UMR 7257, Campus de Luminy, Case 932, Marseille, France
| | - Silvia Spinelli
- Aix-Marseille Université, Architecture et Fonction des Macromolécules Biologiques, UMR 7257, Campus de Luminy, Case 932, Marseille, France
- Centre National de la Recherche Scientifique, Architecture et Fonction des Macromolécules Biologiques, UMR 7257, Campus de Luminy, Case 932, Marseille, France
| | - Stéphanie Blangy
- Aix-Marseille Université, Architecture et Fonction des Macromolécules Biologiques, UMR 7257, Campus de Luminy, Case 932, Marseille, France
- Centre National de la Recherche Scientifique, Architecture et Fonction des Macromolécules Biologiques, UMR 7257, Campus de Luminy, Case 932, Marseille, France
| | - Alain Roussel
- Aix-Marseille Université, Architecture et Fonction des Macromolécules Biologiques, UMR 7257, Campus de Luminy, Case 932, Marseille, France
- Centre National de la Recherche Scientifique, Architecture et Fonction des Macromolécules Biologiques, UMR 7257, Campus de Luminy, Case 932, Marseille, France
| | - Eric Durand
- Aix-Marseille Université, Architecture et Fonction des Macromolécules Biologiques, UMR 7257, Campus de Luminy, Case 932, Marseille, France
- Centre National de la Recherche Scientifique, Architecture et Fonction des Macromolécules Biologiques, UMR 7257, Campus de Luminy, Case 932, Marseille, France
| | - Yannick R. Brunet
- Laboratoire d’Ingénierie des Systèmes Macromoléculaires, Institut de Microbiologie de la Méditerranée, Centre National de la Recherche Scientifique UMR7255, Aix-Marseille Université, Marseille, France
| | - Eric Cascales
- Laboratoire d’Ingénierie des Systèmes Macromoléculaires, Institut de Microbiologie de la Méditerranée, Centre National de la Recherche Scientifique UMR7255, Aix-Marseille Université, Marseille, France
| | - Christian Cambillau
- Aix-Marseille Université, Architecture et Fonction des Macromolécules Biologiques, UMR 7257, Campus de Luminy, Case 932, Marseille, France
- Centre National de la Recherche Scientifique, Architecture et Fonction des Macromolécules Biologiques, UMR 7257, Campus de Luminy, Case 932, Marseille, France
- * E-mail:
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26
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Russell AB, Peterson SB, Mougous JD. Type VI secretion system effectors: poisons with a purpose. Nat Rev Microbiol 2014; 12:137-48. [PMID: 24384601 DOI: 10.1038/nrmicro3185] [Citation(s) in RCA: 501] [Impact Index Per Article: 50.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The type VI secretion system (T6SS) mediates interactions between a broad range of Gram-negative bacterial species. Recent studies have led to a substantial increase in the number of characterized T6SS effector proteins and a more complete and nuanced view of the adaptive importance of the system. Although the T6SS is most often implicated in antagonism, in this Review, we consider the case for its involvement in both antagonistic and non-antagonistic behaviours. Clarifying the roles that type VI secretion has in microbial communities will contribute to broader efforts to understand the importance of microbial interactions in maintaining human and environmental health, and will inform efforts to manipulate these interactions for therapeutic or environmental benefit.
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Affiliation(s)
- Alistair B Russell
- Department of Microbiology, University of Washington, Seattle, Washington 98195, USA
| | - S Brook Peterson
- Department of Microbiology, University of Washington, Seattle, Washington 98195, USA
| | - Joseph D Mougous
- Department of Microbiology, University of Washington, Seattle, Washington 98195, USA
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27
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Benz J, Meinhart A. Antibacterial effector/immunity systems: it's just the tip of the iceberg. Curr Opin Microbiol 2013; 17:1-10. [PMID: 24581686 DOI: 10.1016/j.mib.2013.11.002] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2013] [Revised: 10/31/2013] [Accepted: 11/09/2013] [Indexed: 01/22/2023]
Abstract
Bacteria do not live anchoretic; rather they are constantly in touch with their eukaryotic hosts and with other bacteria sharing their habitat. Therefore, bacteria have evolved sophisticated proteinaceous weapons. To harm other bacteria, they produce antibacterial effector proteins, which they either release into the environment or export via direct intercellular contact. Contact-dependent killing is mediated by two specialized secretion systems, the type V and VI secretion system, whereas contact-independent processes hijack other transport mechanisms. Regardless of the transport system, cells co-express immunity proteins to protect themselves from suicide and fratricide. In general, effector protein activities and secretion mechanisms differ between Gram-positive and Gram-negative bacteria and evidence is emerging that different effector/immunity systems act synergistically and thus extend the bacterial armory.
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Affiliation(s)
- Juliane Benz
- Department of Biomolecular Mechanisms, Max-Planck Institute for Medical Research, Jahnstrasse 29, 69120 Heidelberg, Germany
| | - Anton Meinhart
- Department of Biomolecular Mechanisms, Max-Planck Institute for Medical Research, Jahnstrasse 29, 69120 Heidelberg, Germany.
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28
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Srikannathasan V, English G, Bui NK, Trunk K, O’Rourke PEF, Rao VA, Vollmer W, Coulthurst SJ, Hunter WN. Structural basis for type VI secreted peptidoglycan DL-endopeptidase function, specificity and neutralization in Serratia marcescens. ACTA CRYSTALLOGRAPHICA. SECTION D, BIOLOGICAL CRYSTALLOGRAPHY 2013; 69:2468-82. [PMID: 24311588 PMCID: PMC3852654 DOI: 10.1107/s0907444913022725] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/16/2013] [Accepted: 08/13/2013] [Indexed: 11/10/2022]
Abstract
Some Gram-negative bacteria target their competitors by exploiting the type VI secretion system to extrude toxic effector proteins. To prevent self-harm, these bacteria also produce highly specific immunity proteins that neutralize these antagonistic effectors. Here, the peptidoglycan endopeptidase specificity of two type VI secretion-system-associated effectors from Serratia marcescens is characterized. These small secreted proteins, Ssp1 and Ssp2, cleave between γ-D-glutamic acid and L-meso-diaminopimelic acid with different specificities. Ssp2 degrades the acceptor part of cross-linked tetratetrapeptides. Ssp1 displays greater promiscuity and cleaves monomeric tripeptides, tetrapeptides and pentapeptides and dimeric tetratetra and tetrapenta muropeptides on both the acceptor and donor strands. Functional assays confirm the identity of a catalytic cysteine in these endopeptidases and crystal structures provide information on the structure-activity relationships of Ssp1 and, by comparison, of related effectors. Functional assays also reveal that neutralization of these effectors by their cognate immunity proteins, which are called resistance-associated proteins (Raps), contributes an essential role to cell fitness. The structures of two immunity proteins, Rap1a and Rap2a, responsible for the neutralization of Ssp1 and Ssp2-like endopeptidases, respectively, revealed two distinct folds, with that of Rap1a not having previously been observed. The structure of the Ssp1-Rap1a complex revealed a tightly bound heteromeric assembly with two effector molecules flanking a Rap1a dimer. A highly effective steric block of the Ssp1 active site forms the basis of effector neutralization. Comparisons with Ssp2-Rap2a orthologues suggest that the specificity of these immunity proteins for neutralizing effectors is fold-dependent and that in cases where the fold is conserved sequence differences contribute to the specificity of effector-immunity protein interactions.
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Affiliation(s)
- Velupillai Srikannathasan
- Division of Biological Chemistry and Drug Discovery, College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland
| | - Grant English
- Division of Molecular Microbiology, College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland
| | - Nhat Khai Bui
- Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle upon Tyne NE2 4HH, England
| | - Katharina Trunk
- Division of Molecular Microbiology, College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland
| | - Patrick E. F. O’Rourke
- Division of Biological Chemistry and Drug Discovery, College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland
| | - Vincenzo A. Rao
- Division of Biological Chemistry and Drug Discovery, College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland
| | - Waldemar Vollmer
- Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle upon Tyne NE2 4HH, England
| | - Sarah J. Coulthurst
- Division of Molecular Microbiology, College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland
| | - William N. Hunter
- Division of Biological Chemistry and Drug Discovery, College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland
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29
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Wang T, Ding J, Zhang Y, Wang DC, Liu W. Complex structure of type VI peptidoglycan muramidase effector and a cognate immunity protein. ACTA CRYSTALLOGRAPHICA. SECTION D, BIOLOGICAL CRYSTALLOGRAPHY 2013; 69:1889-900. [PMID: 24100309 PMCID: PMC3792639 DOI: 10.1107/s090744491301576x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/09/2013] [Accepted: 06/06/2013] [Indexed: 11/19/2022]
Abstract
The type VI secretion system (T6SS) is a bacterial protein-export machine that is capable of delivering virulence effectors between Gram-negative bacteria. The T6SS of Pseudomonas aeruginosa transports two lytic enzymes, Tse1 and Tse3, to degrade cell-wall peptidoglycan in the periplasm of rival bacteria that are competing for niches via amidase and muramidase activities, respectively. Two cognate immunity proteins, Tsi1 and Tsi3, are produced by the bacterium to inactivate the two antibacterial effectors, thereby protecting its siblings from self-intoxication. Recently, Tse1-Tsi1 has been structurally characterized. Here, the structure of the Tse3-Tsi3 complex is reported at 1.9 Å resolution. The results reveal that Tse3 contains a C-terminal catalytic domain that adopts a soluble lytic transglycosylase (SLT) fold in which three calcium-binding sites were surprisingly observed close to the catalytic Glu residue. The electrostatic properties of the substrate-binding groove are also distinctive from those of known structures with a similar fold. All of these features imply that a unique catalytic mechanism is utilized by Tse3 in cleaving glycosidic bonds. Tsi3 comprises a single domain showing a β-sandwich architecture that is reminiscent of the immunoglobulin fold. Three loops of Tsi3 insert deeply into the groove of Tse3 and completely occlude its active site, which forms the structural basis of Tse3 inactivation. This work is the first crystallographic report describing the three-dimensional structure of the Tse3-Tsi3 effector-immunity pair.
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Affiliation(s)
- Tianyu Wang
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, People’s Republic of China
- University of Chinese Academy of Sciences, Beijing 100049, People’s Republic of China
| | - Jinjing Ding
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, People’s Republic of China
| | - Ying Zhang
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, People’s Republic of China
| | - Da-Cheng Wang
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, People’s Republic of China
| | - Wei Liu
- Institute of Immunology, The Third Military Medical University, Chongqing 400038, People’s Republic of China
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30
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Li L, Zhang W, Liu Q, Gao Y, Gao Y, Wang Y, Wang DZ, Li Z, Wang T. Structural Insights on the bacteriolytic and self-protection mechanism of muramidase effector Tse3 in Pseudomonas aeruginosa. J Biol Chem 2013; 288:30607-30613. [PMID: 24025333 DOI: 10.1074/jbc.c113.506097] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
The warfare among microbial species as well as between pathogens and hosts is fierce, complicated, and continuous. In Pseudomonas aeruginosa, the muramidase effector Tse3 (Type VI secretion exported 3) can be injected into the periplasm of neighboring bacterial competitors by a Type VI secretion apparatus, eventually leading to cell lysis and death. However, P. aeruginosa protects itself from lysis by expressing immune protein Tsi3 (Type six secretion immunity 3). Here, we report the crystal structure of the Tse3-Tsi3 complex at 1.8 Å resolution, revealing that Tse3 possesses one open accessible, goose-type lysozyme-like domain with peptidoglycan hydrolysis activity. Calcium ions bind specifically in the Tse3 active site and are identified to be crucial for its bacteriolytic activity. In combination with biochemical studies, the structural basis of self-protection mechanism of Tsi3 is also elucidated, thus providing an understanding and new insights into the effectors of Type VI secretion system.
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Affiliation(s)
- Lianbo Li
- From the Laboratory for Computational Chemistry and Drug Design and
| | - Weili Zhang
- From the Laboratory for Computational Chemistry and Drug Design and
| | - Qisong Liu
- Key Laboratory of Chemical Genomics, School of Chemical Biology & Biotechnology, Peking University, Shenzhen Graduate School, Shenzhen 518055, China
| | - Yu Gao
- From the Laboratory for Computational Chemistry and Drug Design and
| | - Ying Gao
- From the Laboratory for Computational Chemistry and Drug Design and
| | - Yun Wang
- From the Laboratory for Computational Chemistry and Drug Design and
| | - David Zhigang Wang
- Key Laboratory of Chemical Genomics, School of Chemical Biology & Biotechnology, Peking University, Shenzhen Graduate School, Shenzhen 518055, China.
| | - Zigang Li
- Key Laboratory of Chemical Genomics, School of Chemical Biology & Biotechnology, Peking University, Shenzhen Graduate School, Shenzhen 518055, China.
| | - Tao Wang
- From the Laboratory for Computational Chemistry and Drug Design and.
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31
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Zhang H, Gao ZQ, Wei Y, Xu JH, Dong YH. Insights into the cross-immunity mechanism within effector families of bacteria type VI secretion system from the structure of StTae4-EcTai4 complex. PLoS One 2013; 8:e73782. [PMID: 24023903 PMCID: PMC3759425 DOI: 10.1371/journal.pone.0073782] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2013] [Accepted: 07/23/2013] [Indexed: 01/06/2023] Open
Abstract
The Gram-negative bacteria type VI secretion system (T6SS) has been found to play an important role in interbacterial competition, biofilm formation and many other virulence-related processes. The bacteria harboring T6SS inject the effectors into their recipient's cytoplasm or periplasm to kill them and meanwhile, to avoid inhibiting itself, the cognate immunity proteins were produced to acts as the effector inhibitor. Tae4 (type VI amidase effector 4) and Tai4 (type VI amidase immunity 4) are newly identified T6SS effector-immunity (EI) pairs. We have recently solved the structures of StTae4-Tai4 and EcTae4-Tai4 complexes from the human pathogens Salmonella typhimurium and Enterobacter cloacae, respectively. It is very interesting and important to discover whether there is cross-neutralization between St- and EcTai4 and whether their effector inhibition mechanism is conserved. Here, we determined the crystal structure of StTae4 in complex with EcTai4. The solution conformation study revealed it is a compact heterotetramer that consists of an EcTai4 homodimer binding two StTae4 molecules in solution, different from that in crystal. A remarkable shift can be observed in both the flexible winding loop of StTae4 and protruding loop of EcTai4 and disulfide bonds are formed to stabilize their overall conformations. The in vitro and in vivo interactions studies showed EcTai4 can efficiently rescue the cells from the toxicity of its cognate effectors StTae4, but can not neutralize the toxic activities of the effectors from other families. These findings provide clear structural evidence to support the previous observation of cross-immunity within T6SS families and provide a basis for understanding their important roles in polymicrobial environments.
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Affiliation(s)
- Heng Zhang
- Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, People’s Republic of China
| | - Zeng-Qiang Gao
- Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, People’s Republic of China
| | - Yong Wei
- Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, People’s Republic of China
- School of Life Sciences, University of Science and Technology of China, Hefei, People’s Republic of China
| | - Jian-Hua Xu
- Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, People’s Republic of China
| | - Yu-Hui Dong
- Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, People’s Republic of China
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32
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Structural insights into the inhibition of type VI effector Tae3 by its immunity protein Tai3. Biochem J 2013; 454:59-68. [DOI: 10.1042/bj20130193] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The recently described T6SS (type VI secretion system) acts as a needle that punctures the membrane of the target cells to deliver effector proteins. Type VI amidase effectors can be classified into four divergent families (Tae1–Tae4). These effectors are secreted into the periplasmic space of neighbouring cells via the T6SS and subsequently rupture peptidoglycan. However, the donor cells are protected from damage because of the presence of their cognate immunity proteins [Tai1 (type VI amidase immunity 1)–Tai4]. In the present paper, we describe the structure of Tae3 in complex with Tai3. The Tae3–Tai3 complex exists as a stable heterohexamer, which is composed of two Tae3 molecules and two Tai3 homodimers (Tae3–Tai34–Tae3). Tae3 shares a common NlpC/P60 fold, which consists of N-terminal and C-terminal subdomains. Structural analysis indicates that two unique loops around the catalytic cleft adopt a closed conformation, resulting in a narrow and extended groove involved in the binding of the substrate. The inhibition of Tae3 is attributed to the insertion of the Ω-loop (loop of α3–α4) of Tai3 into the catalytic groove. Furthermore, a cell viability assay confirmed that a conserved motif (Gln-Asp-Xaa) in Tai3 members may play a key role in the inhibition process. Taken together, the present study has revealed a novel inhibition mechanism and provides insights into the role played by T6SS in interspecific competition.
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33
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Whitney JC, Chou S, Russell AB, Biboy J, Gardiner TE, Ferrin MA, Brittnacher M, Vollmer W, Mougous JD. Identification, structure, and function of a novel type VI secretion peptidoglycan glycoside hydrolase effector-immunity pair. J Biol Chem 2013; 288:26616-24. [PMID: 23878199 DOI: 10.1074/jbc.m113.488320] [Citation(s) in RCA: 90] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Bacteria employ type VI secretion systems (T6SSs) to facilitate interactions with prokaryotic and eukaryotic cells. Despite the widespread identification of T6SSs among Gram-negative bacteria, the number of experimentally validated substrate effector proteins mediating these interactions remains small. Here, employing an informatics approach, we define novel families of T6S peptidoglycan glycoside hydrolase effectors. Consistent with the known intercellular self-intoxication exhibited by the T6S pathway, we observe that each effector gene is located adjacent to a hypothetical open reading frame encoding a putative periplasmically localized immunity determinant. To validate our sequence-based approach, we functionally investigate a representative family member from the soil-dwelling bacterium Pseudomonas protegens. We demonstrate that this protein is secreted in a T6SS-dependent manner and that it confers a fitness advantage in growth competition assays with Pseudomonas putida. In addition, we determined the 1.4 Å x-ray crystal structure of this effector in complex with its cognate immunity protein. The structure reveals the effector shares highest overall structural similarity to a glycoside hydrolase family associated with peptidoglycan N-acetylglucosaminidase activity, suggesting that T6S peptidoglycan glycoside hydrolase effector families may comprise significant enzymatic diversity. Our structural analyses also demonstrate that self-intoxication is prevented by the immunity protein through direct occlusion of the effector active site. This work significantly expands our current understanding of T6S effector diversity.
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34
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Benz J, Reinstein J, Meinhart A. Structural Insights into the Effector - Immunity System Tae4/Tai4 from Salmonella typhimurium. PLoS One 2013; 8:e67362. [PMID: 23826277 PMCID: PMC3695027 DOI: 10.1371/journal.pone.0067362] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2013] [Accepted: 05/17/2013] [Indexed: 11/19/2022] Open
Abstract
Type-6-secretion systems of Gram-negative bacteria are widely distributed needle-like multi-protein complexes that are involved in microbial defense mechanisms. During bacterial competition these injection needles dispense effector proteins into the periplasm of competing bacteria where they induce degradation of the peptidoglycan scaffold and lead to cell lysis. Donor cells co-produce immunity proteins and shuttle them into their own periplasm to prevent accidental toxication by siblings. Recently, a plethora of previously unidentified hydrolases have been suggested to be peptidoglycan degrading amidases. These hydrolases are part of effector/immunity pairs that have been associated with bacterial warfare by type-6-secretion systems. The Tae4 and Tai4 operon encoded by Salmonella typhimurium is one of these newly discovered effector/immunity pairs. The Tae4 effector proteins induce cell lysis by cleaving the γ-D-glutamyl-L-meso-diaminopimelic acid amide bond of acceptor stem muropeptides of the Gram-negative peptidoglycan. Although homologues of the Tae4/Tai4 system have been identified in various different pathogens, little is known about the functional mechanism of effector protein activity and their inhibition by the cognate immunity proteins. Here, we present the high-resolution crystal structure of the effector Tae4 of S. typhimurium in complex with its immunity protein Tai4. We show that Tae4 contains a classical NlpC/P60-peptidase core which is common to other effector proteins of the type-6-secretion system. However, Tae4 has unique structural features that are exclusively conserved within the family of Tae4 effectors and which are important for the substrate specificity. Most importantly, we show that although the overall structure of Tai4 is different to previously described immunity proteins, the essential mode of enzyme inhibition is conserved. Additionally, we provide evidence that inhibition in the Tae4/Tai4 heterotetramer relies on a central Tai4 dimer in order to acquire functionality.
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Affiliation(s)
- Juliane Benz
- Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, Heidelberg, Germany
| | - Jochen Reinstein
- Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, Heidelberg, Germany
| | - Anton Meinhart
- Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, Heidelberg, Germany
- * E-mail:
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35
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Lu D, Shang G, Yu Q, Zhang H, Zhao Y, Cang H, Gu L, Xu S, Huang Y. Expression, purification and preliminary crystallographic analysis of the T6SS effector protein Tse3 from Pseudomonas aeruginosa. Acta Crystallogr Sect F Struct Biol Cryst Commun 2013; 69:524-7. [PMID: 23695568 DOI: 10.1107/s1744309113007148] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2013] [Accepted: 03/14/2013] [Indexed: 01/13/2023]
Abstract
Pseudomonas aeruginosa uses the type VI secretion system (T6SS) to inject effector proteins into rival cells in niche competition. Tse3, one of the effectors of T6SS, is delivered into the periplasm of recipient cells. Tse3 functions as a muramidase that degrades the β-1,4-linkage between N-acetylmuramic acid (MurNAc) and N-acetylglucosamine (GlcNAc) in peptidoglycan, thus leading to lysis of the recipient cells and providing a competitive advantage to the donor cells. Here, the preliminary crystallographic study of Tse3 is reported. A crystal of Tse3 diffracted to 1.5 Å resolution. It belonged to space group C121, with unit-cell parameters a = 166.99, b = 70.13, c = 41.94 Å, α = 90.00, β = 90.52, γ = 90.00° and one molecule per asymmetric unit.
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Affiliation(s)
- Defen Lu
- State Key Laboratory of Microbial Technology, Shandong University, Jinan 250100, PR China
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36
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Tit-for-tat: type VI secretion system counterattack during bacterial cell-cell interactions. Cell 2013; 152:884-94. [PMID: 23415234 DOI: 10.1016/j.cell.2013.01.042] [Citation(s) in RCA: 375] [Impact Index Per Article: 34.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2012] [Revised: 11/08/2012] [Accepted: 01/24/2013] [Indexed: 12/24/2022]
Abstract
The bacterial type VI secretion system (T6SS) is a dynamic organelle that bacteria use to target prey cells for inhibition via translocation of effector proteins. Time-lapse fluorescence microscopy has documented striking dynamics of opposed T6SS organelles in adjacent sister cells of Pseudomonas aeruginosa. Such cell-cell interactions have been termed "T6SS dueling" and likely reflect a biological process that is driven by T6SS antibacterial attack. Here, we show that T6SS dueling behavior strongly influences the ability of P. aeruginosa to prey upon heterologous bacterial species. We show that, in the case of P. aeruginosa, T6SS-dependent killing of either Vibrio cholerae or Acinetobacter baylyi is greatly stimulated by T6SS activity occurring in those prey species. Our data suggest that, in P. aeruginosa, T6SS organelle assembly and lethal counterattack are regulated by a signal that corresponds to the point of attack of the T6SS apparatus elaborated by a second aggressive T6SS(+) bacterial cell. PAPERFLICK:
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37
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Coulthurst SJ. The Type VI secretion system - a widespread and versatile cell targeting system. Res Microbiol 2013; 164:640-54. [PMID: 23542428 DOI: 10.1016/j.resmic.2013.03.017] [Citation(s) in RCA: 135] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2012] [Accepted: 02/05/2013] [Indexed: 12/31/2022]
Abstract
The Type VI secretion system (T6SS) is the most recently described of the Gram-negative bacterial secretion systems and is widely distributed amongst diverse species. T6SSs are currently believed to be complex molecular machines which inject effector proteins into target cells and which incorporate a bacteriophage-like cell-puncturing device. T6SSs have been implicated in eukaryotic cell targeting and virulence in a range of important pathogens. More recently, 'antibacterial' T6SSs have been reported, which are used to efficiently target competitor bacterial cells by the injection of antibacterial toxins. Although it is clear that T6SSs can be deployed as versatile weapons to compete with other bacteria or attack simple or higher eukaryotes, much remains to be determined about this intriguing system.
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Affiliation(s)
- Sarah J Coulthurst
- Department of Molecular Microbiology, College of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, UK.
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38
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Zhang H, Zhang H, Gao ZQ, Wang WJ, Liu GF, Xu JH, Su XD, Dong YH. Structure of the type VI effector-immunity complex (Tae4-Tai4) provides novel insights into the inhibition mechanism of the effector by its immunity protein. J Biol Chem 2013; 288:5928-39. [PMID: 23288853 DOI: 10.1074/jbc.m112.434357] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The type VI secretion system (T6SS), a multisubunit needle-like apparatus, has recently been found to play a role in interspecies interactions. The gram-negative bacteria harboring T6SS (donor) deliver the effectors into their neighboring cells (recipient) to kill them. Meanwhile, the cognate immunity proteins were employed to protect the donor cells against the toxic effectors. Tae4 (type VI amidase effector 4) and Tai4 (type VI amidase immunity 4) are newly identified T6SS effector-immunity pairs. Here, we report the crystal structures of Tae4 from Enterobacter cloacae and Tae4-Tai4 complexes from both E. cloacae and Salmonella typhimurium. Tae4 acts as a DL-endopeptidase and displays a typical N1pC/P60 domain. Unlike Tsi1 (type VI secretion immunity 1), Tai4 is an all-helical protein and forms a dimer in solution. The small angle x-ray scattering study combined with the analytical ultracentrifugation reveal that the Tae4-Tai4 complex is a compact heterotetramer that consists of a Tai4 dimer and two Tae4 molecules in solution. Structure-based mutational analysis of the Tae4-Tai4 interface shows that a helix (α3) of one subunit in dimeric Tai4 plays a major role in binding of Tae4, whereas a protruding loop (L4) in the other subunit is mainly responsible for inhibiting Tae4 activity. The inhibition process requires collaboration between the Tai4 dimer. These results reveal a novel and unique inhibition mechanism in effector-immunity pairs and suggest a new strategy to develop antipathogen drugs.
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Affiliation(s)
- Heng Zhang
- State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, No. 5 Yiheyuan Road, Beijing 100871, China
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English G, Trunk K, Rao VA, Srikannathasan V, Hunter WN, Coulthurst SJ. New secreted toxins and immunity proteins encoded within the Type VI secretion system gene cluster of Serratia marcescens. Mol Microbiol 2012; 86:921-36. [PMID: 22957938 PMCID: PMC3533786 DOI: 10.1111/mmi.12028] [Citation(s) in RCA: 99] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/03/2012] [Indexed: 12/29/2022]
Abstract
Protein secretion systems are critical to bacterial virulence and interactions with other organisms. The Type VI secretion system (T6SS) is found in many bacterial species and is used to target either eukaryotic cells or competitor bacteria. However, T6SS-secreted proteins have proven surprisingly elusive. Here, we identified two secreted substrates of the antibacterial T6SS from the opportunistic human pathogen, Serratia marcescens. Ssp1 and Ssp2, both encoded within the T6SS gene cluster, were confirmed as antibacterial toxins delivered by the T6SS. Four related proteins encoded around the Ssp proteins ('Rap' proteins) included two specifically conferring self-resistance ('immunity') against T6SS-dependent Ssp1 or Ssp2 toxicity. Biochemical characterization revealed specific, tight binding between cognate Ssp-Rap pairs, forming complexes of 2:2 stoichiometry. The atomic structures of two Rap proteins were solved, revealing a novel helical fold, dependent on a structural disulphide bond, a structural feature consistent with their functional localization. Homologues of the Serratia Ssp and Rap proteins are found encoded together within other T6SS gene clusters, thus they represent founder members of new families of T6SS-secreted and cognate immunity proteins. We suggest that Ssp proteins are the original substrates of the S. marcescens T6SS, before horizontal acquisition of other T6SS-secreted toxins. Molecular insight has been provided into how pathogens utilize antibacterial T6SSs to overcome competitors and succeed in polymicrobial niches.
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Affiliation(s)
- Grant English
- Division of Molecular Microbiology, College of Life Sciences, University of DundeeDundee, UK
| | - Katharina Trunk
- Division of Molecular Microbiology, College of Life Sciences, University of DundeeDundee, UK
| | - Vincenzo A Rao
- Division of Biological Chemistry and Drug Discovery, College of Life Sciences, University of DundeeDundee, UK
| | - Velupillai Srikannathasan
- Division of Biological Chemistry and Drug Discovery, College of Life Sciences, University of DundeeDundee, UK
| | - William N Hunter
- Division of Biological Chemistry and Drug Discovery, College of Life Sciences, University of DundeeDundee, UK
| | - Sarah J Coulthurst
- Division of Molecular Microbiology, College of Life Sciences, University of DundeeDundee, UK
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Lossi NS, Manoli E, Simpson P, Jones C, Hui K, Dajani R, Coulthurst SJ, Freemont P, Filloux A. The archetypePseudomonas aeruginosaproteins TssB and TagJ form a novel subcomplex in the bacterial type VI secretion system. Mol Microbiol 2012; 86:437-56. [DOI: 10.1111/j.1365-2958.2012.08204.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/04/2012] [Indexed: 12/25/2022]
Affiliation(s)
- Nadine S. Lossi
- MRC Centre for Molecular Bacteriology and Infection (CMBI); Division of Cell and Molecular Biology; Imperial College London; London; SW7 2AZ; UK
| | - Eleni Manoli
- MRC Centre for Molecular Bacteriology and Infection (CMBI); Division of Cell and Molecular Biology; Imperial College London; London; SW7 2AZ; UK
| | - Pete Simpson
- Division of Molecular Biosciences; Imperial College London; London; SW7 2AZ; UK
| | - Cerith Jones
- MRC Centre for Molecular Bacteriology and Infection (CMBI); Division of Cell and Molecular Biology; Imperial College London; London; SW7 2AZ; UK
| | - Kailyn Hui
- MRC Centre for Molecular Bacteriology and Infection (CMBI); Division of Cell and Molecular Biology; Imperial College London; London; SW7 2AZ; UK
| | - Rana Dajani
- MRC Centre for Molecular Bacteriology and Infection (CMBI); Division of Cell and Molecular Biology; Imperial College London; London; SW7 2AZ; UK
| | - Sarah J. Coulthurst
- Division of Molecular Microbiology; College of Life Sciences; University of Dundee; Dow Street; Dundee; DD1 5EH; UK
| | - Paul Freemont
- Division of Molecular Biosciences; Imperial College London; London; SW7 2AZ; UK
| | - Alain Filloux
- MRC Centre for Molecular Bacteriology and Infection (CMBI); Division of Cell and Molecular Biology; Imperial College London; London; SW7 2AZ; UK
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