Water-soluble hepatic growth hormone receptors: structural studies using gel chromatography and chemical cross-linking.
Water-soluble hepatic growth hormone receptors: structural studies using gel chromatography and chemical cross-linking.
复制标题
水溶性肝生长激素受体：使用凝胶色谱和化学交联进行结构研究。
作者：
S. Ymer;A. Herington
从兔肝中提取的人生长激素(HGH)结合蛋白的凝胶过滤表明，聚乙二醇沉淀法测定的结合物种摩尔质量大于或等于30万。相反，125I-hGH结合蛋白复合体的凝胶过滤显示，主要结合物种的摩尔质量约为100,000。聚乙二醇沉淀法不能检测到该物种。此外，与125I-牛GH孵育后，同样的结合蛋白也被观察到，但125I-绵羊PRL却没有，这表明它是针对妊娠兔肝的生长激素受体，而不是产乳素受体。在还原和非还原条件下，使用琥珀酸二丁二亚胺和十二烷基硫酸钠凝胶电泳法进行的共价交联研究表明，主要结合亚基的摩尔重量为57,000，以及少量的摩尔重量为124,000种。这些数据表明，结合蛋白的结构不涉及亚基间二硫键，并提示妊娠兔肝的初级hGH结合亚基的摩尔质量为57000，并以二聚体(摩尔质量100-124,000)的形式自然存在，可能存在摩尔质量t大于或等于300,000的较大低聚物。
Gel filtration of a water-solubilized human GH (hGH)-binding protein from rabbit liver has indicated that the binding species as determined by polyethylene glycol precipitation, was of mol wt greater than or equal to 300,000. In contrast, gel filtration of 125I-hGH-binding protein complex revealed in addition a major binding species of mol wt approximately 100,000. This species was shown not to be detectable by polyethylene glycol precipitation. Further, this same binding protein was observed after incubation with 125I-bovine GH but not 125I-ovine PRL, suggesting that it was specific for the somatotrophic but not lactogenic receptor of pregnant rabbit liver. Covalent cross-linking studies using disuccinimidyl suberate and sodium dodecyl sulfate gel electrophoresis, under reducing and nonreducing conditions, revealed a predominant binding subunit of mol wt 57,000, as well as smaller amounts of a mol wt 124,000 species. These data indicate that the structure of the binding protein involves no intersubunit disulfide bonds and suggest that the primary hGH binding subunit of pregnant rabbit liver has a mol wt of 57,000 and exists naturally as a dimer (mol wt, 100-124,000) and perhaps larger oligomers of mol wt greater than or equal to 300,000.