title: Type VI secretion system translocates a phage tail spike-like protein into target cells where it cross-links actin.
abstract: Genes encoding type VI secretion systems (T6SS) are widely distributed in pathogenic Gram-negative bacterial species. In Vibrio cholerae, T6SS have been found to secrete three related proteins extracellularly, VgrG-1, VgrG-2, and VgrG-3. VgrG-1 can covalently cross-link actin in vitro, and this activity was used to demonstrate that V. cholerae can translocate VgrG-1 into macrophages by a T6SS-dependent mechanism. Protein structure search algorithms predict that VgrG-related proteins likely assemble into a trimeric complex that is analogous to that formed by the two trimeric proteins gp27 and gp5 that make up the baseplate "tail spike" of Escherichia coli bacteriophage T4. VgrG-1 was shown to interact with itself, VgrG-2, and VgrG-3, suggesting that such a complex does form. Because the phage tail spike protein complex acts as a membrane-penetrating structure as well as a conduit for the passage of DNA into phage-infected cells, we propose that the VgrG components of the T6SS apparatus may assemble a "cell-puncturing device" analogous to phage tail spikes to deliver effector protein domains through membranes of target host cells.
authors.affiliation: Department of Microbiology and Molecular Genetics, Harvard Medical School, 200 Longwood Avenue, Boston, MA 02115, USA.
authors.forename: Stefan
authors.initials: S
authors.lastname: Pukatzki
authors.forename: Amy T
authors.initials: AT
authors.lastname: Ma
authors.forename: Andrew T
authors.initials: AT
authors.lastname: Revel
authors.forename: Derek
authors.initials: D
authors.lastname: Sturtevant
authors.forename: John J
authors.initials: JJ
authors.lastname: Mekalanos
mesh_terms: D000199:Actins / Q000737:chemistry / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000737:chemistry; D000818:Animals; D001435:Bacteriophages / Q000378:metabolism; D001692:Biological Transport; D003432:Cross-Linking Reagents / Q000737:chemistry; D004247:DNA / Q000378:metabolism; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism; D004023:Dictyostelium / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D011487:Protein Conformation; D017434:Protein Structure, Tertiary
chemical_list: D000199:Actins; D003432:Cross-Linking Reagents; D000255:Adenosine Triphosphate; D004247:DNA; C034970:bacteriophage T7 induced DNA polymerase; D004259:DNA-Directed DNA Polymerase