Hydrophobic mismatch between proteins and lipids in membranes

This review addresses the possible consequences of a mismatch in length bet ween the hydrophobic part of membrane-spanning proteins and the hydrophobic bilayer thickness for membrane structure and function. Overviews are given first of the results of studies in defined model systems. These studies ad dress effects of mismatch on protein activity, stability, orientation, aggr egational state, localization, and conformation. With respect to the lipids , effects of mismatch are discussed on lipid chain order, phase transition temperature, lipid phase behavior, and microdomain formation. From these st udies, it is concluded that hydrophobic mismatch can strongly affect protei n and lipid organization, but that the precise consequences depend on the i ndividual properties of the proteins and lipids. Examples of these properti es include the propensity of lipids to form non-lamellar structures, the am ino acid composition of the hydrophobic transmembrane segments of the prote ins, the nature of the membrane anchoring residues, and the number of trans membrane helices. Finally, the effects of mismatch in biological membranes are discussed and its possible consequences for functional membrane process es, such as protein sorting, protein insertion, and regulation of bilayer t hickness. (C) 1998 Elsevier Science B.V. All rights reserved.