Protein targeting by the bacterial twin-arginine translocation (Tat) pathway

The Tat (twin-arginine translocation) protein export system is found in the cytoplasmic membrane of most prokaryotes; and is dedicated to the transport of folded proteins. The Tat system is now known to be essential for many bacterial processes including energy metabolism, cell wall biosynthesis, the nitrogen-fixing symbiosis and bacterial pathogenesis. Recent studies demonstrate that substrate-specific accessory proteins prevent improperly assembled substrates from interacting with the Tat transporter. During the transport cycle itself substrate proteins bind to a receptor complex in the membrane which then recruits a protein-translocating channel to carry out the transport reaction.