Effect of membrane potential on the conformation of bacteriorhodopsin reconstituted in lipid vesicles.

The effect of applied diffusion potential on circular dichroism (CD) of bacteriorhodopsin, reconstituted in lipid vesicles, was measured. The change in CD indicates that the applied electrical field, irrespective of its direction, decreases the alpha-helical fraction and increases the random fraction of the protein. The results are interpreted by unfolding of edges of the helices, upon their submerging into polar environment when the lipid bilayer is electrostricted or (and) the helices are stretched by the electrical field across the membrane.