title: Identification of divergent type VI secretion effectors using a conserved chaperone domain.
abstract: The type VI secretion system (T6SS) is a lethal weapon used by many bacteria to kill eukaryotic predators or prokaryotic competitors. Killing by the T6SS results from repetitive delivery of toxic effectors. Despite their importance in dictating bacterial fitness, systematic prediction of T6SS effectors remains challenging due to high effector diversity and the absence of a conserved signature sequence. Here, we report a class of T6SS effector chaperone (TEC) proteins that are required for effector delivery through binding to VgrG and effector proteins. The TEC proteins share a highly conserved domain (DUF4123) and are genetically encoded upstream of their cognate effector genes. Using the conserved TEC domain sequence, we identified a large family of TEC genes coupled to putative T6SS effectors in Gram-negative bacteria. We validated this approach by verifying a predicted effector TseC in Aeromonas hydrophila. We show that TseC is a T6SS-secreted antibacterial effector and that the downstream gene tsiC encodes the cognate immunity protein. Further, we demonstrate that TseC secretion requires its cognate TEC protein and an associated VgrG protein. Distinct from previous effector-dependent bioinformatic analyses, our approach using the conserved TEC domain will facilitate the discovery and functional characterization of new T6SS effectors in Gram-negative bacteria.
authors.affiliation: Ecosystem and Public Health, Faculty of Veterinary Medicine, University of Calgary, Calgary, AB, Canada T2N 4Z6; Snyder Institute for Chronic Diseases, University of Calgary, Calgary, AB, Canada T2N 4Z6; Biochemistry and Molecular Biology, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada T2N 4Z6.
authors.forename: Xiaoye
authors.initials: X
authors.lastname: Liang
authors.affiliation: Ecosystem and Public Health, Faculty of Veterinary Medicine, University of Calgary, Calgary, AB, Canada T2N 4Z6; Snyder Institute for Chronic Diseases, University of Calgary, Calgary, AB, Canada T2N 4Z6; Biochemistry and Molecular Biology, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada T2N 4Z6.
authors.forename: Richard
authors.initials: R
authors.lastname: Moore
authors.affiliation: Ecosystem and Public Health, Faculty of Veterinary Medicine, University of Calgary, Calgary, AB, Canada T2N 4Z6; Snyder Institute for Chronic Diseases, University of Calgary, Calgary, AB, Canada T2N 4Z6; Biochemistry and Molecular Biology, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada T2N 4Z6.
authors.forename: Mike
authors.initials: M
authors.lastname: Wilton
authors.affiliation: Ecosystem and Public Health, Faculty of Veterinary Medicine, University of Calgary, Calgary, AB, Canada T2N 4Z6; Snyder Institute for Chronic Diseases, University of Calgary, Calgary, AB, Canada T2N 4Z6; Biochemistry and Molecular Biology, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada T2N 4Z6.
authors.forename: Megan J Q
authors.initials: MJ
authors.lastname: Wong
authors.affiliation: Ecosystem and Public Health, Faculty of Veterinary Medicine, University of Calgary, Calgary, AB, Canada T2N 4Z6; Snyder Institute for Chronic Diseases, University of Calgary, Calgary, AB, Canada T2N 4Z6; Biochemistry and Molecular Biology, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada T2N 4Z6.
authors.forename: Linh
authors.initials: L
authors.lastname: Lam
authors.affiliation: Ecosystem and Public Health, Faculty of Veterinary Medicine, University of Calgary, Calgary, AB, Canada T2N 4Z6; Snyder Institute for Chronic Diseases, University of Calgary, Calgary, AB, Canada T2N 4Z6; Biochemistry and Molecular Biology, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada T2N 4Z6 tdong@ucalgary.ca.
authors.forename: Tao G
authors.initials: TG
authors.lastname: Dong
mesh_terms: D000333:Aeromonas / Q000187:drug effects / Q000378:metabolism; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D058947:Bacterial Secretion Systems; D017124:Conserved Sequence; D007109:Immunity / Q000187:drug effects; D018832:Molecular Chaperones / Q000737:chemistry* / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects; D017434:Protein Structure, Tertiary; D014734:Vibrio cholerae / Q000187:drug effects / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D058947:Bacterial Secretion Systems; D018832:Molecular Chaperones
keywords: antitoxin; colicin; interspecies interaction; protein secretion; toxin