Conserved amino acids in F-helix of bacteriorhodopsin form part of a retinal binding pocket.

A 3-dimensional model for the retinal binding pocket in the light-driven proton pump, bacteriorhodopsin, is proposed on the basis of spectroscopic studies of bacteriorhodopsin mutants. In this model Trp-182, Pro-186 and Trp-189 surround the polyene chain while Tyr-185 is positioned close to the retinylidene Schiff base. This model is supported by sequence homologies in the F-helices of bacteriorhodopsin and the related retinal proteins, halorhodopsin and rhodopsins.