tatABC

TatABC refers to the core membrane-embedded complex of the bacterial twin-arginine translocation (Tat) pathway, composed of TatA, TatB, and TatC. It mediates the Sec-independent export of fully folded proteins across the cytoplasmic membrane, particularly periplasmic enzymes and cofactors. The TatABC complex assembles in the inner membrane and functions as a translocase that recognizes substrates with twin-arginine signal peptides.

TatC serves as the primary receptor for twin-arginine signal peptides and initiates complex formation. TatB is a smaller subunit that cooperates with TatC in forming the receptor and in substrate recruitment, while TatA provides the dynamic, pore-forming component that oligomerizes to create a conducting channel during transport.

Translocation occurs when a substrate bearing a signal peptide with a twin-arginine motif is bound by the Tat receptor complex; TatA subunits assemble to form a conduit, and the folded protein is translocated across the inner membrane powered by the proton motive force. The signal peptide is typically cleaved after export by a signal peptidase.

Distribution and significance: The TatABC translocase is widespread in Gram-negative bacteria and in some Gram-positive species, and is also present in plant plastids that retain the pathway. It is essential for the maturation of several periplasmic proteins and is involved in the secretion of certain virulence factors in pathogens. In biotechnology, the Tat system is exploited to export heterologous proteins that must fold before secretion.

The Tat pathway has been characterized through genetics, biochemistry, and structural studies, which established TatABC as the core components of the membrane translocase.