Schwarz-Ben Meir N, Glaser T, Kosower N S
Department of Human Genetics, Sackler School of Medicine, Tel-Aviv University, Israel.
Biochem J. 1991 Apr 1;275 ( Pt 1)(Pt 1):47-52. doi: 10.1042/bj2750047.
Band 3 protein is a major erythrocyte transmembrane glycoprotein. We compared the degradation of band 3 protein by calpain I (a cytoplasmic, micromolar-Ca2(+)-requiring thiol proteinase) in the cells from old individuals (greater than 70 years old) to that in the cells from young ones (20-30 years old). In the young, little degradation of band 3 protein occurred in calpain-treated erythrocyte ghosts. In the old, significant band 3 protein degradation was found in erythrocyte ghosts treated similarly. The difference between young and old in the susceptibility of band 3 protein to calpain was retained in membrane vesicles (membranes stripped of peripheral proteins by NaOH) and in chymotrypsin-generated 60 kDa fragment (CH-60). The isolated N-terminal cytoplasmic 43 kDa fragment was degraded by calpain to a similar extent in old and in young. The separated 17 kDa membrane domain of the CH-60 and the trypsin-generated C-terminal 55 kDa membrane-spanning fragment were not degraded by calpain I in the young, nor in the old. Thus the N-terminal cytoplasmic domain is the domain degraded by calpain I. Enhanced sensitivity in the old is observed in intact band 3 protein and in CH-60, the isolated cytoplasmic domain being equally susceptible in young and old. The observed age-related enhanced sensitivity to calpain is consistent with the presence of modifications in band 3 protein and alterations in the association with the calpain-calpastatin system. Band 3 protein has several important functions, with modifications in the protein having implications for altered cell behaviour in the old individual.
带3蛋白是一种主要的红细胞跨膜糖蛋白。我们比较了钙蛋白酶I（一种细胞质的、需要微摩尔浓度钙离子的巯基蛋白酶）对老年个体（大于70岁）细胞和年轻个体（20 - 30岁）细胞中带3蛋白的降解情况。在年轻人中，经钙蛋白酶处理的红细胞血影中带3蛋白几乎没有降解。在老年人中，类似处理的红细胞血影中发现了明显的带3蛋白降解。带3蛋白对钙蛋白酶敏感性的年轻与老年差异在膜泡（用氢氧化钠去除外周蛋白的膜）和胰凝乳蛋白酶产生的60 kDa片段（CH - 60）中依然存在。分离出的N端细胞质43 kDa片段在老年人和年轻人中被钙蛋白酶降解的程度相似。CH - 60分离出的17 kDa膜结构域和胰蛋白酶产生的C端55 kDa跨膜片段在年轻人和老年人中都不被钙蛋白酶I降解。因此，N端细胞质结构域是被钙蛋白酶I降解的结构域。在完整的带3蛋白和CH - 60中观察到老年人中敏感性增强，而分离出的细胞质结构域在年轻人和老年人中同样敏感。观察到的与年龄相关的对钙蛋白酶敏感性增强与带3蛋白的修饰以及与钙蛋白酶 - 钙蛋白酶抑制蛋白系统的关联改变相一致。带3蛋白具有多种重要功能，该蛋白的修饰对老年个体细胞行为的改变有影响。
