Helmerhorst E
Biochem Biophys Res Commun. 1987 Aug 31;147(1):399-407. doi: 10.1016/s0006-291x(87)80135-3.
The dissociation of insulin from its receptor is reportedly enhanced when the dissociation is induced by dilution in the presence of insulin. This experiment is frequently conducted when curvilinear Scatchard plots of insulin binding are observed in order to infer negative cooperative site-site interactions amongst insulin receptors. However, when insulin binding to purified liver plasma membranes was measured at 15 degrees C in 50 mM Tris, pH 7.5 containing 0.1% bovine serum albumin and 100 U/ml bacitracin, the insulin binding data was characterised by a linear Scatchard plot and a Hill plot with a slope equal to unity. Thus, under the conditions of this binding assay, insulin apparently bound to a single non-interacting class of homogeneous binding sites. But, despite the apparent absence of cooperative interactions under these specific conditions, the dissociation of receptor-bound insulin was still enhanced when the dissociation of insulin from its receptor was induced by dilution in the presence of insulin. This result cast serious doubt on the validity of inferring negative-cooperative site-site interactions amongst insulin receptors based solely on the observation that the dissociation of receptor-bound insulin is enhanced by dilution in the presence of insulin.
据报道，当在胰岛素存在的情况下通过稀释诱导胰岛素与其受体解离时，这种解离会增强。当观察到胰岛素结合的曲线型Scatchard图时，经常进行该实验，以便推断胰岛素受体之间的负协同位点间相互作用。然而，当在含有0.1%牛血清白蛋白和100 U/ml杆菌肽的50 mM Tris（pH 7.5）中于15℃测量胰岛素与纯化的肝细胞膜的结合时，胰岛素结合数据的特征是线性Scatchard图和斜率等于1的Hill图。因此，在该结合测定的条件下，胰岛素显然结合到单一的非相互作用的同类结合位点上。但是，尽管在这些特定条件下明显不存在协同相互作用，但当在胰岛素存在的情况下通过稀释诱导胰岛素与其受体解离时，受体结合的胰岛素的解离仍然会增强。这一结果严重质疑了仅基于在胰岛素存在的情况下通过稀释受体结合的胰岛素的解离增强这一观察结果来推断胰岛素受体之间的负协同位点间相互作用的有效性。
