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Proc Natl Acad Sci U S A. 2015 Jul 21;112(29):9106-11. doi: 10.1073/pnas.1505317112. Epub 2015 Jul 6.

Identification of divergent type VI secretion effectors using a conserved chaperone domain.

Author information

1
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.
2
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.

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.

KEYWORDS:

antitoxin; colicin; interspecies interaction; protein secretion; toxin

PMID:
26150500
PMCID:
PMC4517263
DOI:
10.1073/pnas.1505317112
[Indexed for MEDLINE]
Free PMC Article

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