Peptidyl prolyl isomerase, protein folding role

In vivo, the folding process may be supported by a periplasmic chaperone called Skp. Skp is a 17 kDa protein associated with the plasma membrane that, together with peptidyl prolyl isomerases and disulfideexchanging enzymes, helps folding freshly synthesized proteins in the periplasm (Schafer et al., 1999). Skp binds to partially unfolded polypeptides. Depending on the presence of phospholipids, lipopolysaccharides, and bivalent cations, Skp exists in two conformations, one of which is protease-sensitive (DeCock et al., 1999). Moreover, it was shown that Skp binds to unfolded periplasmic proteins and inserts into phospholipid monolayers, corroborating its putative role as helper in folding and membrane insertion. 

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