Folding alpha-helical membrane proteins: kinetic studies on bacteriorhodopsin.

The correct folding and assembly of proteins within biological membranes is essential for membrane biogenesis and function. In contrast to the large body of work on water-soluble protein folding, however, very little is known about how membrane proteins fold to their final structures. Recent biophysical studies on membrane-protein folding in vitro are beginning to shed light on this problem. In particular, the forces that the membrane lipids impose on the folding protein appear to control certain events. The seven-helix transmembrane protein bacteriorhodopsin has been the focus of much attention and kinetic studies on the folding of this protein form the basis of this review.