Rapoport B, Hazum E, Zor U
J Biol Chem. 1984 Apr 10;259(7):4267-71.
A photoaffinity derivative of human chorionic gonadotropin (hCG-N-hydroxysuccinimidyl-4-azidobenzoate (hCG-HSAB) ) was used to identify components of the lutropin (LH)/hCG receptor in plasma membranes prepared from pregnant mare serum-pretreated rat ovaries. In intact plasma membranes, the Kd for hCG (1 X 10(-10) M) was the same with both 125I-hCG and 125I-hCG-HSAB, and the binding capacity for the photoaffinity label (1 pmol/mg of membrane protein) was the same as for native hCG. Sodium dodecyl sulfate-gel electrophoresis under reducing conditions of 125I-hCG-HSAB cross-linked to plasma membranes revealed newly formed complexes of Mr = 106,000, 85,000, and 80,000 (representing membrane protein components of Mr = 86,000, 65,000, and 60,000, respectively). However, only the Mr = 106,000 complex displayed an affinity for hCG (Kd of 1 X 10(-10) M) consistent with the physiological LH/hCG receptor. The other binding sites were nonsaturable. Half-maximal saturation by 125I-hCG-HSAB of the Mr = 106,000 complex (1-2 X 10(-9) M) was similar to the Kd of the specific binding of 125I-hCG-HSAB to intact plasma membranes (8 X 10(-10) M). The present data suggest that among the different components of the LH/hCG receptor, only one component (of Mr = 86,000) possesses the affinity and binding capacity characteristics of the LH/hCG receptor as determined using radiolabeled, underivatized hCG.
人绒毛膜促性腺激素的光亲和衍生物（hCG-N-羟基琥珀酰亚胺-4-叠氮苯甲酸酯，即hCG-HSAB）被用于鉴定从孕马血清预处理的大鼠卵巢制备的质膜中促黄体生成素（LH）/hCG受体的成分。在完整的质膜中，hCG（1×10⁻¹⁰ M）对于¹²⁵I-hCG和¹²⁵I-hCG-HSAB的解离常数（Kd）相同，并且光亲和标记物的结合容量（1 pmol/mg膜蛋白）与天然hCG相同。在还原条件下，将¹²⁵I-hCG-HSAB与质膜交联后进行十二烷基硫酸钠-凝胶电泳，结果显示新形成的分子量分别为106,000、85,000和80,000的复合物（分别代表分子量为86,000、65,000和60,000的膜蛋白成分）。然而，只有分子量为106,000的复合物对hCG表现出亲和力（Kd为1×10⁻¹⁰ M），这与生理性LH/hCG受体一致。其他结合位点是不饱和的。¹²⁵I-hCG-HSAB对分子量为106,000复合物的半数最大饱和度（1 - 2×10⁻⁹ M）与¹²⁵I-hCG-HSAB与完整质膜特异性结合的Kd（8×10⁻¹⁰ M）相似。目前的数据表明，在LH/hCG受体的不同成分中，只有一种成分（分子量为86,000）具有使用放射性标记的未衍生化hCG测定的LH/hCG受体的亲和力和结合容量特征。
