InterPro domain: IPR002033

Proteins encoded by the mttABC operon (formerly yigTUW), mediate a novel Sec-independent membrane targeting and translocation system in Escherichia coli that interacts with cofactor-containing redox proteins having a S/TRRXFLK "twin arginine" leader motif. This family contains the E. coli mttB gene (TATC) [ 1 ].

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 E. coli TatC protein are essential for protein export. At least two TatC molecules co-exist within each Tat translocon [ 2 , 3 ].

1. A novel and ubiquitous system for membrane targeting and secretion of cofactor-containing proteins. Cell 93, 93-101
2. Overlapping functions of components of a bacterial Sec-independent protein export pathway. EMBO J. 17, 3640-50
3. Topology determination and functional analysis of the Escherichia coli TatC protein. FEBS Lett. 525, 65-70