Enhanced translocation of recombinant proteins via the Tat pathway with chaperones in Escherichia coli

The twin-arginine translocation (Tat) pathway is capable of translocating folded proteins into the periplasm of Gram-negative bacteria and thus holds great potential for the expression of recombinant proteins in Escherichia coli. Nevertheless, this promise has been hampered by the low translocation efficiency. In this study, we demonstrate that the co-expression of DmsD, a system specific cytoplasmic chaperone similar to TorD, in conjunction with the DmsA signal peptide can enhance the translocation of the GFP fusion protein by 28.2%. We further show the presence of cross-activity between DmsD and TorD for the DmsA and TorA leader-fusions. The co-expression of DmsD and TorD enhances the translocation of ssTorA-GFP fusion and ssDmsA-GFP fusion by 28.6% and 46.6%, respectively. It was also observed that the co-expression of DmsD led to a reduction in the formation of GFP inclusion bodies, whereas the co-expression of TorD primarily led to a reduction in proteolysis by the Clp system. It is concluded that DmsD and TorD enhance protein translocation via the Tat pathway by providing activity against protein aggregation and/or proteolysis.