Arakaki R F, Comi R J, Gorden P
Diabetes Branch, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, Maryland 20892.
Biochem Biophys Res Commun. 1989 Apr 14;160(1):296-302. doi: 10.1016/0006-291x(89)91655-0.
The insulin receptor is synthesized as a single chain, 190 kDa glycoprotein precursor, which undergoes proteolytic cleavage, carbohydrate processing, and fatty acylation to generate the mature receptor on the plasma membrane. The relationship of these post-translational modifications to the acquisition of receptor function, i.e. ligand binding and phosphokinase activity, is not fully understood. Therefore, the 190 kDa proreceptor and mature receptor kinase activities were separately examined in vitro, and their phosphorylation properties compared. The solubilized receptor precursor from IM-9 lymphocytes was purified by sequential lectin chromatography and, following site specific anti-receptor antibody immunoprecipitation, phosphokinase studies performed. The isolated proreceptor was activated by insulin and phosphorylated exogenous substrate alpha-casein, as similarly observed for the mature receptor. Structurally, the phosphorylated proreceptor was identified as a 360 kDa homodimer under non-reducing condition.
胰岛素受体最初作为一条单链190 kDa的糖蛋白前体合成，该前体经过蛋白水解切割、碳水化合物加工和脂肪酰化，从而在质膜上生成成熟受体。这些翻译后修饰与受体功能（即配体结合和磷酸激酶活性）获得之间的关系尚未完全明确。因此，分别在体外检测了190 kDa前体受体和成熟受体的激酶活性，并比较了它们的磷酸化特性。通过连续的凝集素层析法纯化来自IM-9淋巴细胞的可溶受体前体，在进行位点特异性抗受体抗体免疫沉淀后，开展磷酸激酶研究。如成熟受体一样，分离得到的前体受体可被胰岛素激活并使外源性底物α-酪蛋白磷酸化。在结构上，磷酸化的前体受体在非还原条件下被鉴定为360 kDa的同型二聚体。
