[Study of rhodopsin sulfhydryl groups in the photoreceptor membrane]

The interaction between rhodopsin SH-groups in the photoreceptor membrane suspension with different titrating reagents (Ag HOGM, DTNB) was studied. After rhodopsin bleaching the number of free SH-groups increased from two in the dark to six after illumination. Such increase of SH-groups number was observed only by the amperometric titration procedure. The influence of the "dark" and "light exposed" SH-group modifications on regeneration ability of rhodopsin in the presence of 11-cis-retinal was investigated. No dependence of regeneration on SH-groups modification in the dark was observed, while modification of "light" SH-groups decreases rhodopsin regeneration ability. The distribution of SH-groups in rhodopsin molecules and SH-groups dependence on protein conformation are discussed.