Webb C F, Wallis M
Biochemistry Laboratory, School of Biological Sciences, University of Sussex, Falmer, Brighton, U.K.
Biochem J. 1988 Feb 15;250(1):215-9. doi: 10.1042/bj2500215.
Lactogenic receptors were analysed with the use of the cross-linking agent disuccinimidyl suberate to attach covalently 125I-labelled ovine prolactin or human growth hormone to binding sites from (1) liver from pregnant rats and (2) the rat-derived Nb2 lymphoma cell line. Analysis by SDS/polyacrylamide-gel electrophoresis of the proteins cross-linked to labelled hormone in rat liver indicated a major specifically-labelled complex with an Mr of 68,000-72,000, when run under reducing or non-reducing conditions. With Nb2 cells a major specifically-labelled complex with an Mr of 97,000-110,000 was identified, but only when electrophoresis was run using reducing conditions. Assuming one hormone molecule (Mr 22,000-24,000) per hormone-receptor complex, then the receptor proteins have an Mr of 44,000-50,000 for rat liver and 73,000-88,000 for the Nb2 cells. For both cell types the receptors were of lactogenic specificity; lactogenic hormones competed for binding whereas somatogenic hormones did not. These studies suggest that the lactogenic receptors in rat liver membranes and Nb2 cells differ in two respects. Firstly, the Mr of the labelled receptor protein in Nb2 cells is greater than that of the corresponding receptor protein in rat liver membranes; secondly, the Nb2 cell receptor appears to exist as a disulphide-linked oligomer whereas the receptor in rat liver membranes does not.
使用交联剂辛二酸二琥珀酰亚胺酯将125I标记的绵羊催乳素或人生长激素共价连接到（1）妊娠大鼠肝脏和（2）大鼠来源的Nb2淋巴瘤细胞系的结合位点上，对催乳素受体进行分析。通过SDS/聚丙烯酰胺凝胶电泳分析大鼠肝脏中与标记激素交联的蛋白质，结果表明，在还原或非还原条件下进行电泳时，主要的特异性标记复合物的Mr为68,000 - 72,000。对于Nb2细胞，仅在使用还原条件进行电泳时，才鉴定出一种主要的特异性标记复合物，其Mr为97,000 - 110,000。假设每个激素-受体复合物中有一个激素分子（Mr 22,000 - 24,000），那么大鼠肝脏的受体蛋白Mr为44,000 - 50,000，Nb2细胞的受体蛋白Mr为73,000 - 88,000。对于这两种细胞类型，受体都具有催乳素特异性；催乳素能竞争结合，而生长激素则不能。这些研究表明，大鼠肝细胞膜和Nb2细胞中的催乳素受体在两个方面存在差异。首先，Nb2细胞中标记受体蛋白的Mr大于大鼠肝细胞膜中相应受体蛋白的Mr；其次，Nb2细胞受体似乎以二硫键连接的寡聚体形式存在，而大鼠肝细胞膜中的受体则不是。
