title: Effect of light-adaptation on the binding of 48-kDa protein (S-antigen) to photoreceptor cell membranes.
abstract: During the process of light-adaptation, a part of retinal S-antigen ("48-kDa protein") is bound to the photoreceptor cell membranes. This fraction can be isolated by first extracting the soluble S-antigen with isotonic buffer and subsequently extracting the bound S-antigen with detergent. In this way we found that light-adaptation to 250 lx or more induces a maximum binding of 62% of total S-antigen within 2 minutes in rat retina in vivo. At low light intensity (50 lx) this process lasts 15 minutes, while at 5 lx only 30% of S-antigen is bound. Presumably the number of available phosphorylated (bleached) rhodopsin molecules is the limiting factor in time and quantity. Dark-adaptation causes an initial rapid release of S-antigen during the first 5 minutes, but it takes more than 2 hours to reach the minimum level of about 10% bound S-antigen. The rates of binding of S-antigen in the light and of release of S-antigen in the dark are compared to other phenomena of light and dark adaptation.
mesh_terms: D000221:Adaptation, Ocular; D000818:Animals; D000941:Antigens / Q000378:metabolism*; D019393:Arrestin; D002462:Cell Membrane / Q000276:immunology; D003623:Dark Adaptation; D005136:Eye Proteins / Q000378:metabolism*; D008027:Light; D008297:Male; D010786:Photoreceptor Cells / Q000276:immunology* / Q000648:ultrastructure; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D000941:Antigens; D019393:Arrestin; D005136:Eye Proteins