CRABP cytoplasmic retinoic acid-binding

After entering the cell, retinol and retinoic acid (RA) are bound by separate cytoplasmic proteins. These cytosolic proteins are called cytoplasmic-retinol binding protein (CRBP) artd cytoplasmic retinoic acid-binding protein (CRABP). Two forms of CRBP exist, and tw o forms of CRABP exist. One form of CRiiP occurs mainly In the villi of the small intestines, while the other form occurs in the liver and other organs. One form of CRABP occurs in the skin, while the other form occurs in many tissues. 

Retinoic acid receptors (RARs) have been detected m nuclear extracts from various cell types on the basis of their ability to bind radiolabeled retinoic acid (1 3). Prior to the isolation of RAR cDNAs in 1987 (4,5), biochemical evidence for the existence of nuclear retinoic-acid binding proteins distinct from cytoplasmic CRABP had been obtained (1). The techniques used in these experiments can be used to study the biochemical properties of the RARs and may also be applicable to the study of the related receptors known as RXRs, which bind 9-cis retinoic acid with high affinity (6). 

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