VISININ - A NOVEL CALCIUM-BINDING PROTEIN EXPRESSED IN RETINAL CONE CELLS

Visinin is a retinal cone cell-specific protein (molecular weight 24,000, pl 5.1). To investigate its function, visinin cDNA was isolated from a chick retinal λgt11 cDNA library, using anti-visinin serum. The (β-galactosidase-visinin fusion protein was used for purifying epitope-selected antibody. The purified visinin antibody reacted only with a 24 kd protein in retinal cone cells. Visinin mRNA was expressed only in the retinal photoreceptor layer. The nucleotide sequence of the cDNA revealed that visinin has three E-F hand structures and is a Ca2+ binding protein. Visinin protein expressed in E. coli exhibited Ca2+ binding activity. These results suggest that visinin is a photoreceptor-specific Ca2+ binding protein and may be involved in phototransduction in the cone cells. © 1990.