A monomer-dimer model explains the results of radiation inactivation: binding characteristics of insulin receptor purified from human placenta.
A monomer-dimer model explains the results of radiation inactivation: binding characteristics of insulin receptor purified from human placenta.
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单体-二聚体模型解释了辐射失活的结果：从人胎盘中纯化的胰岛素受体的结合特征。
DOI：
10.1021/bi00409a020
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发表时间：
1988
期刊：
影响因子：
2.9
通讯作者：
Harmon,JT
中科院分区：
文献类型：
--
作者：
Fujita-Yamaguchi,Y;Harmon,JT
1988年1月5日收到的修订版摘要：辐射灭活技术已用于高度纯化的人胎盘胰岛素受体，以确定负责胰岛素结合的功能分子大小并评估“亲和力调节剂”假说，该假说已被提出来解释在低辐射剂量下观察到的与大鼠肝膜的特异性胰岛素结合的增加[Harmon，J. T.，Hedo，J.A.，& Kahn，C. R.（1983）J.Biol.Chem.258，6875-6881]，观察到三种不同类型的失活曲线：（1）暴露于低辐射剂量后结合活性增强的双相，（2）暴露于低辐射剂量后结合活性无变化的非线性，和（3）随着辐射暴露的增加结合活性损失的线性。单体-二聚体模型是最简单的模型，最好地描述了观察到的三种类型的辐射灭活曲线。该模型预测，当初始二聚体/单体比等于或大于1且单体比二聚体更活跃时，暴露于低辐射剂量后会导致胰岛素结合活性增加。用此模型估算了结合活性的单体大小为227000道尔顿。该值很可能反映了单体α型的大小。为了证实这一模型，通过Sepharose CL-6 B层析对纯化的受体进行分级分离。该柱的胰岛素结合曲线显示两个峰。进一步的研究表明：（i）峰I（α 2/？2-富集）和峰II（a/3-富集）受体分别显示曲线Scatchard图和直线Scatchard图，和（ii）在我们的标准条件下[50 mM tris]，峰I受体的比活性估计为峰II受体的26（羟甲基）氨基甲烷盐酸盐，pH 7.4]，这些研究表明，亲和力调节因子并不作为一个单独的结构蛋白存在，而是由于受体的二聚体形式。二聚体形式（α 2/32）具有比单体α形式低得多的胰岛素结合比活性（在标准条件下），但二聚体结构是观察负协同结合等温线所必需的。胰岛素受体是一种膜糖蛋白，其负责将信号从靶细胞的外部传递到内部并导致胰岛素依赖性生物学作用（Kahn等人，1981年）。的结构
Revised Manuscript Received January 5, 1988 abstract: The technique of radiationinactivation has been used on highly purified human placental insulin receptor in order to determine the functional molecular size responsible for the insulin binding and to evaluate the “affinity regulator” hypothesis, which has been proposed to explain the increase in specific insulin binding to rat liver membranes observed at low radiation doses [Harmon, J. T., Hedo, J. A., & Kahn, C. R.(1983) J. Biol. Chem. 258, 6875-6881], Three different types of inactivation curves were observed:(1) biphasic with an enhanced binding activity after exposure to low radiation doses,(2) nonlinear with no change in binding activity after exposure to low radiation doses, and (3) linear with a loss in the binding activity with increasing radiation exposures. A monomer-dimer model was the simplest model that best described the three types of radiation inactivation curves observed. The model predicts that an increase ininsulin binding activity would result after exposure to low radiation doses when the initial dimer/monomer ratio is equal to or greater than 1 and a monomer is more active than a dimer. The monomer size of the bindingactivity was estimated to be 227 000daltons by this model. This value most likely reflects the size of the monomeric afi form. To substantiate this model, the purified receptor was fractionated bySepharose CL-6B chro-matography. The insulin binding profile of this column indicated two peaks. Further studies revealed the following:(i) peak I (a2/? 2-rich) and peak II (a/3-rich) receptors showed curvilinear Scatchard plotsand straight Scatchard plots, respectively, and (ii) specific activity of the peak I receptors was estimated to be 26% of that of the peak II receptors under our standard conditions [50 mM tris (hydroxymethyl) aminomethane hydrochloride, pH 7.4], These studiessuggest that the affinity regulator does not exist as a separate structural protein but is dueto the dimeric form of the receptor. The dimeric form (a2/32) possesses a much lower specific activity for insulin binding than does the monomeric afi form (underthe standard conditions), but the dimeric structure is necessary to observe the negative cooperative binding isotherm. e insulin receptor is a membrane glycoprotein that is re-sponsible for transferring the signal from the exterior to the interior of target cells and leading to insulin-dependent biological actions (Kahn et al., 1981). The structure of the