Chen C, Schilling K, Hiipakka R A, Huang I Y, Liao S
J Biol Chem. 1982 Jan 10;257(1):116-21.
alpha-Protein, a major glycoprotein in the cytosol fraction of rat ventral prostate, has a molecular weight of about 50,000 and can be dissociated, by sodium dodecyl sulfate, into two different subunits (A and B). alpha-Protein has three different polypeptide components with apparent molecular weights of 10,000 (I), 14,000 (II), and 15,000 (III). These components were purified to homogeneity and their amino acid compositions were determined. Subunit A is composed of Components I and III, whereas subunit B is composed of Components II and III. Carbohydrate was detectable only on Component III. Component III isolated from subunit A and Component III isolated from subunit B appear to be identical. The purified alpha-protein contains 0.7-1 mol of cholesterol/mol of protein. If cholesterol was removed by acetone, about 1 mol of 5 alpha-dihydrotestosterone or pregnenolone could bind to 1 mol of alpha-protein. In the presence of 2 mM ZnCl2, alpha-protein can form dimers and tetramers. In cell-free systems, alpha-protein can inhibit binding of the androgen-receptor complex to nuclear chromatin and also can promote the release of the complex already bound to chromatin. This effect is due to polypeptide Component I.
α蛋白是大鼠腹侧前列腺胞质溶胶部分的一种主要糖蛋白，分子量约为50,000，可被十二烷基硫酸钠解离成两种不同的亚基（A和B）。α蛋白有三种不同的多肽成分，表观分子量分别为10,000（I）、14,000（II）和15,000（III）。这些成分被纯化至同质，并测定了它们的氨基酸组成。亚基A由成分I和III组成，而亚基B由成分II和III组成。仅在成分III上可检测到碳水化合物。从亚基A分离出的成分III和从亚基B分离出的成分III似乎是相同的。纯化的α蛋白每摩尔蛋白质含有0.7 - 1摩尔胆固醇。如果用丙酮去除胆固醇，约1摩尔的5α-二氢睾酮或孕烯醇酮可与1摩尔α蛋白结合。在2 mM ZnCl2存在下，α蛋白可形成二聚体和四聚体。在无细胞系统中，α蛋白可抑制雄激素受体复合物与核染色质的结合，也可促进已结合到染色质上的复合物的释放。这种作用归因于多肽成分I。
