National Center for
2P5Z: The E. Coli C3393 Protein Is A Component Of The Type Vi Secretion System And Exhibits Structural Similarity To T4 Bacteriophage Tail Proteins Gp27 And Gp5
Type VI secretion apparatus and phage tail-associated protein complexes share a common evolutionary origin
Proc. Natl. Acad. Sci. U. S. A. (2009) 106 p.4154-4159
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.