ABSTRACT
This chapter considers related aspects of the bio-organic chemistry of vision. It deals with the mechanism by which photolyzed rhodopsin achieves that conformational state, which is capable of catalyzing the exchange of guanosine triphosphatase for GDP in the retinal G-protein. The chapter is concerned with the beginnings of the identification and characterization of that hitherto elusive process responsible for the isomerization of an all-fra/i.y-retinoid to an 11-cis-retinoid. The question is how the charge is redistributed as a consequence of the absorption of light. One possible mechanism would involve the light-induced redistribution of charge down the carbon backbone of the retinoid. Returning to the rhodopsin modification studies, the fact that permethylated rhodopsin was capable of activating the G-protein as well as rhodopsin itself led to the question of the possible roles of the nonactive-site lysine residues in the interaction with the G-protein.
