Clark S, DeLuise M, Larkins R G, Melick R A, Harrison L C
Biochem J. 1978 Jul 15;174(1):37-43. doi: 10.1042/bj1740037.
The role of the surrounding membrane structure on the binding characteristics of the insulin receptor was studied by using several digestive enzymes. The effects observed with particulate membrane preparations are compared with those from soluble receptor preparations. beta-Galactosidase and neuraminidase had no effect on insulin binding to either particulate or soluble receptors from human placentae. Exposure to 2 units of phospholipase C/ml increased insulin binding to particulate membranes, but was without effect on the soluble receptor preparation. The increase in binding to particulate membranes was shown to be due to an increase in apparent receptor number. After 5 min exposure to 500 microgram of trypsin/ml there was an increase in insulin binding to the particulate membrane fraction, owing to an increase in receptor affinity. After 15 min exposure to this amount of trypsin, binding decreased, owing to a progressive decrease in receptor availability. In contrast, this concentration of trypsin had no effect on the solubilized receptor preparation. Because of the differential effects of phospholipase C and trypsin on the particulate compared with the solubilized receptor preparations, it is concluded that the effects of these enzymes were due to an effect on the surrounding membrane structure. Changes in receptor configuration due to alterations within the adjoining membrane provide a potential mechanism for mediating short-term alterations in receptor function.
利用几种消化酶研究了周围膜结构对胰岛素受体结合特性的作用。将颗粒状膜制剂观察到的效应与可溶性受体制剂的效应进行了比较。β-半乳糖苷酶和神经氨酸酶对胰岛素与人胎盘颗粒状或可溶性受体的结合均无影响。每毫升加入2单位磷脂酶C可增加胰岛素与颗粒状膜的结合，但对可溶性受体制剂无影响。与颗粒状膜结合的增加表明是由于表观受体数量增加所致。每毫升暴露于500微克胰蛋白酶5分钟后，由于受体亲和力增加，胰岛素与颗粒状膜部分的结合增加。暴露于该量胰蛋白酶15分钟后，由于受体可用性逐渐降低，结合减少。相比之下，该浓度的胰蛋白酶对可溶性受体制剂无影响。由于磷脂酶C和胰蛋白酶对颗粒状受体制剂与可溶性受体制剂的作用不同，得出结论：这些酶的作用是由于对周围膜结构的影响。相邻膜内改变导致的受体构象变化为介导受体功能的短期改变提供了一种潜在机制。
