小牛睾丸中G蛋白对FSH受体亲和性和腺苷酸环化酶活性的调节

本文用NEM(N-ethylmaleimide)为探针研究了G蛋白(鸟嘌呤核苷酸调节蛋白,Gp)对小牛睾丸中FSH受体的亲和性及腺苷酸环化酶活性的调节作用。证据表明,①在小牛睾丸细胞膜G蛋白上存在两种类型鸟嘌呤核苷酸结合位点(下简称GTP结合位点),高亲和性低容量结合位点及低亲和性高容量结合位点;②高亲和性结合位点(对NEM敏感)调节腺苷酸环化酶活性,而对NEM相对不敏感的低亲和性位点则不直接参与该酶活性的调节;③G蛋白对受体亲和性的调节则不仅要高亲和性位点的参与,而且主要受低亲和性位点的调节。

Regulation of Follitropin Receptor Affinity And Adenylate Cyclase Activity on Plasma Membrane of Bovine Calf Testis by G Protein

In this study we examined the regulation of follitropin(FSH)receptor affi-nity and adenylate cyclase activity by guanine nucleotide binding protein(Gp) .It was shown by evidence that (1) there were two classes of guanine nucleotide binding sites on the Gp of calf testis membranes, high affinity (with low capacity) binding sites and low affinity (with high capacity) binding sites; (2) it seemed to be that the high affinity GTP binding sites which were sensitive to NEM modulated the activity of adenylate cyclase; and (3) the regulation of receptor affinity for FSH by Gp mainly required the low affinity GTP binding sites to be occupied.