Enhanced solubility of heterologous proteins by fusion expression using stress-induced Escherichia coli protein, Tsf

Through two-dimensional electrophoresis, Escherichia coli proteome response to a protein denaturant, guanidine hydrochloride, was analyzed and elongation factor Ts (Tsf) detected as a stress-induced protein. Many host proteins aggregated, or their synthesis levels decreased significantly under conditions of protein denaturation as 34 out of 699 soluble proteins knocked out and 63 proteins decreased by over 2.5-fold. Interestingly, the expression level of Tsf increased 1.61-fold compared with a nonstress condition. Contrary to direct expression, various heterologous proteins were solubly expressed in E. coli when subjected to N-terminus fusions of Tsf. Owing most likely to an intrinsic high folding efficiency, Tsf seemed to play critical roles in sequestering interactive surfaces of heterologous proteins from nonspecific protein-protein interactions leading to formation of inclusion bodies. It has been also demonstrated that Tsf is effective in aiding the production of a biologically active bacterial cutinase, which could be of interest to biotechnology and commercial applications.