107] Isolation of cellular retinoid-binding proteins from bovine retina with bound endogenous ligands

Abstract

This chapter discusses the isolation of cellular retinoid-binding proteins from bovine retina with bound endogenous ligands. The recent discovery of a group of intracellular retinoid-binding proteins seems to provide intracellular counterparts to serum retinol-binding protein (SRBP) and to be in accord with the notion that retinoids are rarely encountered uncomplexed in higher organisms. Although the functions of these cellular binding proteins are not yet understood, it is expected that they will be found to play a role in the intracellular transport and metabolism of the vitamin and perhaps mediate some of its biological effects. Three cellular retinoid-binding proteins have been purified to apparent homogeneity from bovine retina. Because of the specificity of these proteins for particular retinoids and their intracellular localization, they have been termed the cellular retinol-binding protein (CRBP), cellular retinoic acid-binding protein (CRABP), and cellular retinal-binding protein (CRALBP).