Kinetic study of transfer of 11- cis-Retinal between rod outer segment membranes using regeneration of rhodopsin

Abstract

The present study demonstrates some important facts on the regeneration of rhodopsin in rod outer segment membranes. 11- cis-Retinal added to a rod outer segment membrane suspension did not react directly with opsin but was rapidly solubilized into membranes and then recombined with opsin in the membrane. It was also revealed that the regeneration of rhodopsin was perturbed by the formation of retinylidene Schiff base with phosphatidylethanolamine in rod outer segment membranes, which decreased with increasing temperature. The activation energy of rhodopsin regeneration in rod outer segment membranes was 18.7 kcal/mol, being smaller than the value of 22 kcal/mol in 1% digitonin solution. 11- cis-Retinal could be found to transfer relatively fast (τ-1/ k 1 R̃ 10 3 s) between rod outer segment membranes by using the regeneration of rhodopsin. It was demonstrated that the kinetic measurement for the transport of membrane-soluble molecules such as retinal between membranes could be perform ed with ease and precisely by the method described in this paper.