The SurA periplasmic PPlase lacking its parvulin domains functions in vivoand has chaperone activity

The Escherichia coil periplasmic peptidyl-prolyl isomerase (PPIase) SurA is involved in the maturation of outer membrane porins, SurA consists of a su bstantial N-terminal region, two iterative parvulin-like domains and a C-te rminal tail. Here we show that a variant of SurA lacking both parvulin-like domains exhibits a PPIase-independent chaperone-like activity in vitro and almost completely complements the in vivo function of intact SurA. SurA in teracts preferentially (>50-fold) with in vitro synthesized porins over oth er similarly sized proteins, leading us to suggest that the chaperone-like function of SurA preferentially facilitates maturation of outer membrane pr oteins.