Ymer S I, Herington A C
Endocrinology. 1984 May;114(5):1732-9. doi: 10.1210/endo-114-5-1732.
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.
对兔肝脏中水溶性人生长激素（hGH）结合蛋白进行凝胶过滤分析表明，通过聚乙二醇沉淀法测定的结合物质分子量大于或等于300,000。相比之下，对125I-hGH结合蛋白复合物进行凝胶过滤分析还发现了一种主要的结合物质，其分子量约为100,000。聚乙二醇沉淀法无法检测到该物质。此外，用125I-牛生长激素孵育后可观察到相同的结合蛋白，但用125I-羊催乳素孵育后则未观察到，这表明它对孕兔肝脏的生长激素受体具有特异性，而对催乳素受体没有特异性。在还原和非还原条件下，使用辛二酸二琥珀酰亚胺酯进行共价交联研究并结合十二烷基硫酸钠凝胶电泳分析，结果显示主要的结合亚基分子量为57,000，还有少量分子量为124,000的物质。这些数据表明，该结合蛋白的结构不涉及亚基间二硫键，提示孕兔肝脏中主要的hGH结合亚基分子量为57,000，天然状态下以二聚体（分子量100,000 - 124,000）形式存在，可能还存在分子量大于或等于300,000的更大寡聚体。
