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Cellular Retinoid-Binding Proteins
David E. Ong, PhD
Arch Dermatol. 1987;123(12):1693-1695a.
Abstract
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A number of specific carrier proteins for members of the vitamin A family have been discovered. Two of these proteins bind all-trans-retinol and are found within cells important in vitamin A metabolism or function. These two proteins have considerable sequence homology and have been named cellular retinol-binding protein (CRBP) and cellular retinol-binding protein, type II (CRBP [II] ). A third intracellular protein, cellular retinoic acid-binding protein (CRABP) also is structurally similar but binds only retinoic acid. Although retinol appears to be bound quite similarly by the two retinol-binding proteins, subtle differences are apparent that appear to be related to the different functions of the two proteins. That, coupled with the specific cellular locations of the two proteins, suggests their roles. Cellular retinol-binding protein appears to have several roles, including (1) delivering retinol to specific binding sites within the nucleus and (2) participating in the transepithelial movement of retinol across certain blood-organ barriers. In contrast, CRBP (II) appears to be involved in the intestinal absorption of vitamin A and, in particular, may direct retinol to a specific esterifying enzyme, resulting in the production of fatty acyl esters of retinol that are incorporated into chylomicrons for release to the lymph. Like CRBP, CRABP can deliver its ligand retinoic acid to specific binding sites within the nucleus, sites different from those for retinol. The nuclear binding of retinol and retinoic acid may be part of the mechanism by which vitamin A directs the state of differentiation of epithelial tissue.
(Arch Dermatol 1987;123:1693-1695a)
Author Affiliations
From the Department of Biochemistry, Vanderbilt University, Nashville, Tenn.
Footnotes
Accepted for publication July 13, 1987.
Read before the 36th Annual Symposium on the Biology of Skin ("Molecular Basis of Nutritional Dermatoses"), Salishan Lodge, Gleneden Beach, Ore, Oct 20, 1986.
Reprint requests to Department of Biochemistry, Vanderbilt University, Nashville, TN 37232 (Dr Ong).
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