Abstract
Orientation and location of retinal in bovine rhodopsin have been determined by cross-linking studies with a photoactivatable analog of 11-cis retinal and by site-directed mutagenesis. The two approaches are corroborative and we identified Glu-122 and Trp-126 in helix C and Trp-265 and Tyr-268 in helix F as a part of retinal binding pocket. Our results also suggest that the β-ionone ring of retinal orients towards helices C and F from the Schiff base end in helix G. Recent mutagenesis studies regarding the counter ion to the protonated Schiff base were also discussed.
