Affinity of the periplasmic chaperone Skp of Escherichia coli for phospholipids, lipopolysaccharides and non-native outer membrane proteins - Role ofSkp in the biogenesis of outer membrane protein

The Skp protein of Escherichia coil has been proposed to be a periplasmic m olecular chaperone involved in the biogenesis of outer membrane proteins. I n this study, evidence is obtained that Skp exists in two different states characterized by their different sensitivity to proteases. The conversion b etween these states can be modulated in vitro by phospholipids, lipopolysac charides and bivalent cations. Sh-p is able to associate with and insert in to phospholipid membranes in vitro, indicating that it may associate with p hospholipids in the inner and/or outer membrane in vivo. In addition, it in teracts specifically with outer membrane proteins that are in their non-nat ive state. We propose that Skp is required in vivo for the efficient target ing of unfolded outer membrane proteins to the membrane.