The bacterial Tat protein translocation system is different with the Sec machinery which is general protein translocation system in the bacteria, but similar to ΔpH-dependent pathway used for importing chloroplast proteins into the thylakoid. This system can export proteins with a twin-arginine signal peptide bearing a consensus (S/T)-R-R-x-F-L-K motif and in the folded conformation. Moreover most of these proteins are always containing redox cofactor enzymes with relations to the bacterial anaerobic respiratory. This protein translocation system is affected by a kind of factors such as the twin arginines in the consensus motif, the hydrophobicity of h-region, sec-avoidance signal of the c-region of the signal peptide and the constitution of mature proteins. And there are four proteins (TatA,TatB,TatC and TatE) involved with this system of E.coli.