Wecksler W R, Ross F P, Mason R S, Norman A W
J Clin Endocrinol Metab. 1980 Jan;50(1):152-7. doi: 10.1210/jcem-50-1-152.
Specific cytoplasmic receptors for 1 alpha,25-dihydroxyvitamin D3 are shown to be present in human intestinal cytosol which are very similar to the analogous 1 alpha,25-dihydroxyvitamin D3 receptors present in chick intestinal cytosol. Both receptors are 3.5S proteins which aggregate under low ionic strength conditions. They have molecular weights of approximately 60,000 and Stokes' molecular radii of 33 A. The equilibrium dissociation constants for the receptors were both 2 X 10(-10) M at 4 C. The association rate constant for the human receptor was found to be 2.5 X 10(7) M-1 min-1 at 0 C, while a value of 0.5 X 10(7) M-1 min-1 was obtained for the chick receptor. The dissociation rate constants at 4 C were 6.4 X 10(-4) min-1 (human) and 3.6 X 10(-5) min-1 (chick). In addition, it was found that both receptors possessed reduced cysteine residues near the 1 alpha,25-dihydroxyvitamin D3-binding site which were critical for receptor-binding activity. The similarities between the human and the chick receptors suggests that homologous mechanisms for 1 alpha,25-dihydroxyvitamin D3 interactions may be at work in both mammalian and avian intestinal systems.
研究表明，人肠细胞溶质中存在1α,25 - 二羟基维生素D3的特异性细胞质受体，这些受体与鸡肠细胞溶质中类似的1α,25 - 二羟基维生素D3受体非常相似。两种受体均为3.5S蛋白，在低离子强度条件下会聚集。它们的分子量约为60,000，斯托克斯分子半径为33 Å。两种受体在4℃时的平衡解离常数均为2×10⁻¹⁰ M。发现人受体在0℃时的结合速率常数为2.5×10⁷ M⁻¹ min⁻¹，而鸡受体的值为0.5×10⁷ M⁻¹ min⁻¹。4℃时的解离速率常数分别为6.4×10⁻⁴ min⁻¹（人）和3.6×10⁻⁵ min⁻¹（鸡）。此外，还发现两种受体在1α,25 - 二羟基维生素D3结合位点附近都有减少的半胱氨酸残基，这些残基对受体结合活性至关重要。人和鸡受体之间的相似性表明，1α,25 - 二羟基维生素D3相互作用的同源机制可能在哺乳动物和鸟类肠道系统中都起作用。
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