Nishimura R, Raymond M J, Ji I, Rebois R V, Ji T H
Proc Natl Acad Sci U S A. 1986 Sep;83(17):6327-31. doi: 10.1073/pnas.83.17.6327.
Human choriogonadotropin (hCG) is a heterodimeric hormone composed of an alpha and a beta subunit. hCG and its asialo (ashCG) and deglycosylated (dghCG) forms vary in their ability to stimulate hormone responsive adenylate cyclase. ashCG is a partial agonist, and dghCG is an antagonist. Photoactivatable moieties were coupled to hCG, ashCG, and dghCG, and the derivatives were radioiodinated. Competitive binding studies indicate that all of the derivatives had a similar affinity for the gonadotropin receptor on porcine granulosa cell membranes. Radiolabeled derivatives were used to photoaffinity label the gonadotropin receptor. Radiolabeled complexes were separated by NaDodSO4/PAGE. All of the derivatives produced similar autoradiographic patterns, except that dghCG produced an additional 48-kDa complex. To investigate the structure of the complexes further, peptide mapping of proteolytic digests was used. All, except for the 48-kDa complex, generated similar peptide maps indicating a relationship between those complexes in which the smaller components are part of the larger. The 48-kDa complex contained both subunits of 40-kDa dghCG. Therefore, this complex is expected to contain an additional component of 8 kDa. The complex was generated whether the hormone-receptor complex was photoaffinity labeled on cells, on isolated membranes, or after solubilizing in detergent. Formation was blocked by excess hCG and did not occur in the absence of UV irradiation. We conclude that the hCG derivatives are able to photoaffinity label the hCG receptor but that the dghCG derivative can photoaffinity label an additional component that was not observed when derivatives of hCG or ashCG were used to label the receptor.
人绒毛膜促性腺激素（hCG）是一种由α和β亚基组成的异源二聚体激素。hCG及其去唾液酸形式（ashCG）和去糖基化形式（dghCG）在刺激激素反应性腺苷酸环化酶的能力上有所不同。ashCG是一种部分激动剂，而dghCG是一种拮抗剂。将可光活化部分与hCG、ashCG和dghCG偶联，并对衍生物进行放射性碘化。竞争性结合研究表明，所有衍生物对猪颗粒细胞膜上的促性腺激素受体具有相似的亲和力。用放射性标记的衍生物进行光亲和标记促性腺激素受体。放射性标记的复合物通过十二烷基硫酸钠/聚丙烯酰胺凝胶电泳（NaDodSO4/PAGE）分离。除dghCG产生一个额外的48 kDa复合物外，所有衍生物产生相似的放射自显影图谱。为了进一步研究复合物的结构，使用了蛋白水解消化物的肽图谱分析。除48 kDa复合物外，所有复合物产生相似的肽图谱，表明这些复合物之间存在关系，其中较小的组分是较大组分的一部分。48 kDa复合物包含40 kDa dghCG的两个亚基。因此，预计该复合物还包含一个8 kDa的额外组分。无论激素-受体复合物是在细胞上、分离的膜上还是在去污剂中溶解后进行光亲和标记，都会产生该复合物。过量的hCG可阻断其形成，且在没有紫外线照射的情况下不会发生。我们得出结论，hCG衍生物能够对hCG受体进行光亲和标记，但dghCG衍生物能够对一种额外的组分进行光亲和标记，而当使用hCG或ashCG衍生物标记受体时未观察到该组分。
