title: Type VI secretion apparatus and phage tail-associated protein complexes share a common evolutionary origin.
abstract: Protein secretion is a common property of pathogenic microbes. Gram-negative bacterial pathogens use at least 6 distinct extracellular protein secretion systems to export proteins through their multilayered cell envelope and in some cases into host cells. Among the most widespread is the newly recognized Type VI secretion system (T6SS) which is composed of 15-20 proteins whose biochemical functions are not well understood. Using crystallographic, biochemical, and bioinformatic analyses, we identified 3 T6SS components, which are homologous to bacteriophage tail proteins. These include the tail tube protein; the membrane-penetrating needle, situated at the distal end of the tube; and another protein associated with the needle and tube. We propose that T6SS is a multicomponent structure whose extracellular part resembles both structurally and functionally a bacteriophage tail, an efficient machine that translocates proteins and DNA across lipid membranes into cells.
authors.affiliation: Department of Biological Sciences, Purdue University, West Lafayette, IN 47906, USA.
authors.forename: Petr G
authors.initials: PG
authors.lastname: Leiman
authors.forename: Marek
authors.initials: M
authors.lastname: Basler
authors.forename: Udupi A
authors.initials: UA
authors.lastname: Ramagopal
authors.forename: Jeffrey B
authors.initials: JB
authors.lastname: Bonanno
authors.forename: J Michael
authors.initials: JM
authors.lastname: Sauder
authors.forename: Stefan
authors.initials: S
authors.lastname: Pukatzki
authors.forename: Stephen K
authors.initials: SK
authors.lastname: Burley
authors.forename: Steven C
authors.initials: SC
authors.lastname: Almo
authors.forename: John J
authors.initials: JJ
authors.lastname: Mekalanos
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D001435:Bacteriophages / Q000737:chemistry; D005075:Biological Evolution; D017899:Caudovirales / Q000737:chemistry*; D006090:Gram-Negative Bacteria / Q000737:chemistry / Q000472:pathogenicity*; D026901:Membrane Transport Proteins / Q000378:metabolism / Q000502:physiology*; D011487:Protein Conformation; D040681:Structural Homology, Protein; D014764:Viral Proteins / Q000737:chemistry*
chemical_list: D001426:Bacterial Proteins; D026901:Membrane Transport Proteins; D014764:Viral Proteins