Shearer T R, Shih M, Azuma M, David L L
Department of Oral Molecular Biology, Oregon Health Sciences University, Portland 97201, USA.
Exp Eye Res. 1995 Aug;61(2):141-50. doi: 10.1016/s0014-4835(05)80033-8.
The purpose of these experiments was to study the mechanism for precipitation of lens crystallins in cataract. An in vitro model was developed to activate the endogenous protease calpain II in the soluble proteins from young rat lens by addition of calcium in the presence of 120 mM KCl. Light-scattering, insoluble proteins were produced approximately 4-6 days after calpain II activation. Results showed that proteolysis was caused by activation of lens calpain II, proteolysis preceded precipitation by several days, and alpha-crystallin acted as a molecular chaperone against precipitation of crystallins caused by proteolysis. These data supported our hypothesis that calpain-induced proteolysis of the N-terminal arms of beta-crystallin polypeptides leads to a loss of normal oligomerization of beta-crystallin polypeptides and formation of abnormal insoluble aggregates, possibly stabilized by hydrophobic interactions.
这些实验的目的是研究白内障中晶状体蛋白沉淀的机制。通过在120 mM KCl存在的情况下添加钙，开发了一种体外模型来激活幼鼠晶状体可溶性蛋白中的内源性蛋白酶钙蛋白酶II。在钙蛋白酶II激活后约4-6天产生了光散射的不溶性蛋白。结果表明，蛋白水解是由晶状体钙蛋白酶II的激活引起的，蛋白水解比沉淀提前几天发生，并且α-晶状体蛋白作为分子伴侣，可防止蛋白水解引起的晶状体蛋白沉淀。这些数据支持了我们的假设，即钙蛋白酶诱导的β-晶状体蛋白多肽N末端臂的蛋白水解导致β-晶状体蛋白多肽正常寡聚化的丧失和异常不溶性聚集体的形成，这些聚集体可能通过疏水相互作用而稳定。
