Bernstein P S, Choi S Y, Ho Y C, Rando R R
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115.
Proc Natl Acad Sci U S A. 1995 Jan 31;92(3):654-8. doi: 10.1073/pnas.92.3.654.
Retinoid-binding proteins are essential mediators of vitamin A function in vertebrate organisms. They solubilize and stabilize retinoids, and they direct the intercellular and intracellular trafficking, transport, and metabolic function of vitamin A compounds in vision and in growth and development. Although many soluble retinoid-binding proteins and receptors have been purified and extensively characterized, relatively few membrane-associated enzymes and other proteins that interact with retinoids have been isolated and studied, due primarily to their inherent instabilities during purification. In an effort to identify and purify previously uncharacterized retinoid-binding proteins, it is shown that radioactively labeled all-trans-retinoic acid can be used as a photoaffinity labeling reagent to specifically tag two known retinoic acid-binding proteins, cellular retinoic acid-binding protein and albumin, in complex mixtures of cytosolic proteins. Additionally, a number of other soluble and membrane-associated proteins that bind all-trans-[11,12-3H]retinoic acid with high specificity are labeled utilizing the same photoaffinity techniques. Most of these labeled proteins have molecular weights that do not correspond to any known retinoid-binding proteins. Thus, photoaffinity labeling with all-trans-retinoic acid and related photoactivatable retinoids is a method that should prove extremely useful in the identification and purification of novel soluble and membrane-associated retinoid-binding proteins from ocular and nonocular tissues.
类视黄醇结合蛋白是脊椎动物体内维生素A功能的重要介质。它们使类视黄醇溶解并稳定下来，指导维生素A化合物在视觉以及生长发育过程中的细胞间和细胞内运输、转运及代谢功能。尽管许多可溶性类视黄醇结合蛋白和受体已被纯化并得到广泛表征，但相对较少与类视黄醇相互作用的膜相关酶和其他蛋白质被分离和研究，这主要是因为它们在纯化过程中固有的不稳定性。为了鉴定和纯化以前未被表征的类视黄醇结合蛋白，研究表明放射性标记的全反式视黄酸可作为光亲和标记试剂，在细胞溶质蛋白的复杂混合物中特异性标记两种已知的视黄酸结合蛋白，即细胞视黄酸结合蛋白和白蛋白。此外，利用相同的光亲和技术标记了许多其他以高特异性结合全反式-[11,12-³H]视黄酸的可溶性和膜相关蛋白。这些标记蛋白中的大多数分子量与任何已知的类视黄醇结合蛋白都不对应。因此，用全反式视黄酸和相关的可光活化类视黄醇进行光亲和标记是一种在从眼组织和非眼组织中鉴定和纯化新型可溶性和膜相关类视黄醇结合蛋白方面应被证明极其有用的方法。
