The chaperone activity of trigger factor is distinct from its isomerase activity during co-expression with adenylate kinase in Escherichia coli

To investigate the molecular chaperone function of trigger factor (TF) and its relationship with isomerase activity in vivo, the assisted folding of a denylate kinase (AK) by TF in Escherichia coli was examined by measuring th e amounts of soluble AK produced during co-expression. When the mutant of c hicken AK, P17G, is expressed in plasmid pBVAK, 95% of the protein is found in inclusion bodies. Co-expression of AK with TF was achieved using a plas mid pBVAT that allowed expression of TF and AK in the same plasmid under se parate control. Coexpression with TF resulted in an increase in the amount of soluble AK, with a higher increase when TF was expressed at higher level s in the cell. Co-expression of AK with the two TF mutants, Y221G and F233Y , in which peptidyl-prolyl cisltrans isomerase activity was 1%, of wild-typ e, gave the same results as wild-type TF. This provides in vivo evidence th at the molecular chaperone activity of TF is distinct from its isomerase ac tivity. (C) 2001 Published by Elsevier Science B.V. on behalf of the Federa tion of European Biochemical Societies.