David L L, Shearer T R, Shih M
Department of Oral Molecular Biology, Oregon Health Sciences University, Portland 97201.
J Biol Chem. 1993 Jan 25;268(3):1937-40.
Abnormal activation of the protease calpain in the lens may be a cause of cataracts. Cataracts were induced in 10-day-old rats by a single overdose of sodium selenite. The water-insoluble protein from the opaque lens nucleus was separated by two-dimensional electrophoresis, electroblotted onto membranes, and the NH2-terminal sequence of partially degraded beta-crystallin polypeptides determined. Selenite cataractous lenses contained four major structural proteins, beta B1, beta B3, beta A3/A1, and beta A4 crystallins, missing from 5 to 49 amino acids from their NH2 termini. Incubation of intact beta-crystallins with calpain II in vitro produced identical cleavage sites. This provided further evidence for the role of calpain in the production of light scattering insoluble protein in cataractous lenses and also suggested that a similar process may lead to lens protein insolubilization during aging.
晶状体中蛋白酶钙蛋白酶的异常激活可能是白内障的一个成因。通过单次过量注射亚硒酸钠在10日龄大鼠中诱发白内障。从不透明的晶状体核中提取水不溶性蛋白质，通过二维电泳进行分离，电印迹到膜上，并测定部分降解的β-晶状体蛋白多肽的NH2末端序列。亚硒酸钠诱发白内障的晶状体含有四种主要结构蛋白，即βB1、βB3、βA3/A1和βA4晶状体蛋白，其NH2末端缺失5至49个氨基酸。完整的β-晶状体蛋白在体外与钙蛋白酶II孵育产生相同的切割位点。这为钙蛋白酶在白内障晶状体中产生光散射不溶性蛋白质的作用提供了进一步证据，也表明类似过程可能在衰老过程中导致晶状体蛋白不溶性化。
