Insertion and Folding of Outer Membrane Proteins Into Lipid Bilayers and the Function of the Periplasmic Chaperone FkpA

Abstract

In Gram-negative bacteria, outer membrane proteins (OMPs) are translocated in unfolded form across the periplasm before they insert and fold into the outer membrane. When isolated in unfolded form in 8 M urea, OMPs like OmpA develop their barrel structure after urea dilution in the presence of preformed lipid bilayers or detergent micelles. We have previously shown that a periplasmic chaperone, the seventeen kDa protein (Skp) promotes OmpA folding and insertion into lipid bilayers, but only when these bilayers contain negatively charged phosphatidylglycerol [1].