Investigation of the organization of rhodopsin in the sheep photoreceptor membrane by using cross-linking reagents

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Abstract
The organization of rhodopsin in the photoreceptor membrane of sheep rod outer segments was investigated by using a variety of bifunctional reagents. Of the 9 reagents used, 7 gave oligomeric opsin species, whereas 2, copper phenanthroline and dithiobisphenyl azide, failed to cross-link the protein. In general, the cross-linked species obtained showed diminishing yields from dimer to tetramer, together with some higher-MW aggregates. The patterns of cross-linking probably arise as a result of collision complexes and best describe a monomeric organization for native rhodopsin. No significant differences between the patterns obtained with dark-adapted bleached or regenerated protein states were observed. This interpretation is discussed in relation to the postulated mechanism of action of rhodopsin.