Purification of cellular retinaldehyde-binding protein from bovine retina and retinal pigment epithelium.

Cellular retinaldehyde-binding protein (CRALP) has been purified from extracts of bovine retina or retinal pigment epithelium by a procedure employing an initial, high-capacity anion exchange chromatographic step and anion exchange HPLC for removal of a persistent contaminant. The procedure also yields fractions containing three other retinoid-binding proteins present in retina (cellular retinol-, cellular retinoic acid- and interphotoreceptor retinol-binding proteins; CRBP, CRABP and IRBP, respectively). Procedures are described for labeling CRALBP with 9-cis-retinaldehyde, 11-cis-retinaldehyde, or 11-cis-retinol. There are approx. 3 nmol of CRALBP per adult bovine eye and the binding protein is ca. 0.5% of the soluble protein of a retinal supernatant.