The bacterial Tat system has a remarkable ability to transport folded proteins even enzyme complexes across the cytoplasmic membrane. It is structurally and mechanistically similar to the Delta pH-driven thylakoidal protein import pathway. A functional Tat system or Delta pH-dependent pathway requires three integral membrane proteins: TatA/Tha4, TatB/Hcf106 and TatC/cpTatC. The TatC protein is essential for the function of both pathways. It might be involved in twin-arginine signal peptide recognition, protein translocation and proton translocation. Sequence analysis predicts that TatC contains six transmembrane helices (TMHs), and experimental data confirmed that N- and C-termini of TatC or cpTatC are exposed to the cytoplasmic or stromal face of the membrane. The cytoplasmic N-terminus and the first cytoplasmic loop region of the Escherichia coli TatC protein are essential for protein export. At least two TatC molecules co-exist within each Tat translocon [1].

1: Topology determination and functional analysis of the Escherichia coli TatC protein. Gouffi K, Santini CL, Wu LF; FEBS Lett 2002;525:65-70. PMID:12163163