Chvatchko Y, Gazzano H, Van Obberghen E, Fehlmann M
Mol Cell Endocrinol. 1984 Jun;36(1-2):59-65. doi: 10.1016/0303-7207(84)90085-6.
Insulin receptors from rat hepatoma cells were studied by the three following methods. Firstly, the alpha subunit (Mr 130000) was labelled using a 125I-photoreactive insulin analogue and UV irradiation. Secondly, using phosphorylation of partially purified and immunoprecipitated receptors with [gamma-32P]ATP, the beta subunit (Mr 95000) was labelled. Thirdly, both alpha and beta subunits were labelled by surface iodination catalysed by lactoperoxidase followed by cell solubilization and immunoprecipitation of the receptor with anti-receptor antibodies. The results show that the native insulin receptor exists under different forms: free alpha and beta subunits and the following combinations of disulphide-linked oligomers: alpha beta, alpha 2, alpha 2 beta and alpha 2 beta 2. In addition, it appears that there is at least one insulin binding site per alpha subunit, and that the alpha and beta subunits may be in close physical association in the plasma membrane even when they are not linked by disulphide bonds. In intact cells, only the alpha subunit is sensitive to extracellular proteases that cleave preferentially the region of the alpha subunit bearing the sulphydryl groups responsible for the interchain binding.
采用以下三种方法对大鼠肝癌细胞的胰岛素受体进行了研究。首先，使用125I光反应性胰岛素类似物并经紫外线照射对α亚基（分子量130000）进行标记。其次，用[γ-32P]ATP对部分纯化并经免疫沉淀的受体进行磷酸化，从而对β亚基（分子量95000）进行标记。第三，用过氧化物酶催化表面碘化法对α和β亚基进行标记，随后使细胞溶解，并用抗受体抗体对受体进行免疫沉淀。结果表明，天然胰岛素受体以不同形式存在：游离的α和β亚基以及以下二硫键连接的寡聚体组合：αβ、α2、α2β和α2β2。此外，似乎每个α亚基至少有一个胰岛素结合位点，并且即使α和β亚基未通过二硫键连接，它们在质膜中也可能紧密物理结合。在完整细胞中，只有α亚基对细胞外蛋白酶敏感，这些蛋白酶优先切割α亚基上带有负责链间结合的巯基的区域。
