Shin J, Ji I, Ji T H
J Biol Chem. 1986 Jun 5;261(16):7501-6.
Affinity cross-linking of the lutropin receptor with 125I-human choriogonadotropin (hCG) on porcine granulosa cells produced four distinct homone-receptor complexes under reducing conditions. They contain 18-, 24-, 28-, and 34-kDa components (Ji, I., Bock, J. H., and Ji, T. H. (1985) J. Biol. Chem. 260, 12815-12821). Photoaffinity labeling and cross-linking produced 136-, 102-, and 74-kDa hCG-receptor complexes under reducing conditions and the 136-kDa complex under nonreducing conditions. In addition, the unreduced 102-kDa complex was seen in photoaffinity labeling but not in cross-linking. When the unreduced 136-kDa complex was reduced, the 102- and 74-kDa complexes were generated, indicating release of the 34- and the 28-kDa components in two steps. When the unreduced 102-kDa complex was reduced, the 74-kDa complex was produced, indicating the release of a 28-kDa component. The 74-kDa complex could not be reduced but was cleaved by alkaline treatment to produce the hCG alpha beta dimer. The results indicate that the 24-kDa component is released from the 74-kDa complex, since the apparent mass of the hCG alpha beta dimer on gels is 50 kDa. The 24-kDa component appears to be the initial site for photoaffinity labeling or cross-linking and to be disulfide linked to the 28-kDa component which is in turn disulfide linked to the 34-kDa component. These intercomponent disulfides exist in some receptors but not all. Formation of the disulfide-linked 136-kDa band required the presence of a sulfhydryl-blocking agent, N-ethylmaleimide. In particular, the 34-kDa component was vulnerable to reduction. There was no significant evidence of disulfides between the hormone and any of the receptor components.
在还原条件下，猪颗粒细胞上促黄体激素受体与¹²⁵I - 人绒毛膜促性腺激素（hCG）的亲和交联产生了四种不同的激素 - 受体复合物。它们含有18、24、28和34 kDa的组分（季，I.，博克，J. H.，和季，T. H.（1985年）《生物化学杂志》260，12815 - 12821）。光亲和标记和交联在还原条件下产生了136、102和74 kDa的hCG - 受体复合物，在非还原条件下产生了136 kDa的复合物。此外，未还原的102 kDa复合物出现在光亲和标记中，但不出现在交联中。当未还原的136 kDa复合物被还原时，产生了102和74 kDa的复合物，表明34和28 kDa的组分分两步释放。当未还原的102 kDa复合物被还原时，产生了74 kDa的复合物，表明释放了一个28 kDa的组分。74 kDa的复合物不能被还原，但经碱性处理可裂解产生hCGαβ二聚体。结果表明，24 kDa的组分从74 kDa的复合物中释放出来，因为凝胶上hCGαβ二聚体的表观质量为50 kDa。24 kDa的组分似乎是光亲和标记或交联的初始位点，并通过二硫键与28 kDa的组分相连，而28 kDa的组分又通过二硫键与34 kDa的组分相连。这些组分间的二硫键存在于一些受体中，但不是所有受体。二硫键连接的136 kDa条带的形成需要巯基阻断剂N - 乙基马来酰亚胺的存在。特别是，34 kDa的组分易被还原。没有明显证据表明激素与任何受体组分之间存在二硫键。
