Rapid isolation of bovine interphotoreceptor retinol-binding protein.
A large retinol-binding protein, interphotoreceptor retinol-binding protein, is found only in the interphotoreceptor matrix of the eye, and may function in vitamin A transport for the visual cycle. Interphotoreceptor retinol-binding protein is the major glycoprotein of this matrix, and can be isolated rapidly by affinity-adsorption onto concanavalin A-Sepharose. The yield is approx. 0.25 mg per bovine eye. Its apparent Mr is 250000 by gel-filtration chromatography, and 225000 by native polyacrylamide-gradient gel electrophoresis; this protein band displays endogenous retinol fluorescence on such gels. As measured by SDS-polyacrylamide gel electrophoresis, the apparent Mr is 140000. In the interphotoreceptor matrix most vitamin A-binding sites on this retinol-binding protein are unoccupied; however, addition of exogenous all-trans-retinol can saturate these sites. The apparent dissociation constant for retinol is 10(-6) M, as measured by fluorimetric titration.
D000818:Animals; D002417:Cattle; D002846:Chromatography, Affinity; D004591:Electrophoresis, Polyacrylamide Gel; D008027:Light; D008970:Molecular Weight; D010786:Photoreceptor Cells / Q000032:analysis*; D012177:Retinol-Binding Proteins / Q000302:isolation & purification* / Q000378:metabolism; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D014801:Vitamin A / Q000378:metabolism
D012177:Retinol-Binding Proteins; D014801:Vitamin A