Twin-arginine translocation (Tat) pathway
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The twin-arginine translocation, or Tat, pathway is a protein export, or secretion pathway found in plants, bacteria, and archaea. It serves to actively translocate folded proteins across a phospholipid membrane bilayer. In plants, the Tat translocase is found in the thylakoid membrane of the chloroplast, where it acts to import proteins into the chloroplast. In bacteria, the Tat translocase is found in the cytoplasmic membrane and serves to export proteins to the cell envelope, or to the extracellular space [1].
The Tat translocase is composed of the membrane proteins TatA, TatB, and TatC. In Escherichia coli, a fourth gene, tatE encodes a functionally redundant TatA protein. Not all bacteria carry the tatABC genes in their genome[2]; however, of those that do, there seems to be no discrimination between pathogens and nonpathogens. Despite that fact, some pathogenic bacteria such as Pseudomonas aeruginosa, Legionella pneumophila, and E. coli O157:H7 rely on a functioning Tat pathway for full virulence in infection models, indicating that the Tat pathway in these bacteria exports virulence factors.
[edit] References
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[1] Sargent et al., "Pathfinders and trailblazers: a prokaryotic targeting system for transport of folded proteins" FEMS Microbiol Lett, 254 (2):198-207
