Calcium and high molecular weight protein aggregates in bovine and human lens.
Calcium and high molecular weight protein aggregates in bovine and human lens.
复制标题
钙和高分子量蛋白质聚集在牛和人的晶状体中。
DOI：
--
复制
发表时间：
1974
期刊：
影响因子：
--
通讯作者：
K. Krul
中科院分区：
文献类型：
--
作者：
A. Spector;D. Adams;K. Krul
已测定了牛和人透镜蛋白的钙含量。高分子量（HMW）牛α-晶状体蛋白含有比其它可溶性牛透镜蛋白多约3倍的钙，而HMW人透镜蛋白的钙含量比其低分子量（LMW）对应物高约10倍。在4° C下通过彻底透析不能去除钙。pH值为7.6。在更碱性的pH值和更高的温度下，大部分钙可以从牛和人HMW蛋白中消除。需要更高的pH值以获得与用牛HMW α-晶状体蛋白观察到的钙水平相当的HMW人蛋白的钙水平降低。一组潜在的钙结合化合物的研究表明，苏氨酸和青霉胺是最有效的降低高分子量人类透镜蛋白质的钙水平在中性pH值，去除约58%和52%，分别。当牛HMW α-晶状体蛋白的钙水平降低至LMW蛋白中发现的钙水平时，大部分蛋白质转化为LMW物质。从HMW人透镜蛋白中部分去除钙，产生了向LMW蛋白的微小但显著的偏移。人HMW蛋白在除去大部分钙的条件下解聚，然后在存在或不存在5 - 8 mM钙的条件下再聚集，表明该阳离子是大部分蛋白质再聚集成HMW聚集体所必需的。上述观察结果强烈表明，高分子量透镜蛋白的形成需要钙，去除该阳离子将导致还原为低分子量物质。
The calcium content of bovine and human lens proteins has been determined. High molecular weight (HMW) bovine a-crystallin contains about three times more calcium than other soluble bovine lens proteins, while the calcium content of HMW human lens protein is approximately 10 times greater than its low molecular weight (LMW) counterpart. The calcium could not be removed by exhaustive dialysis at 4° C. and a pH of 7.6. At more alkaline pH's and higher temperatures most of the calcium could be eliminated from both bovine and human HMW protein. Higher pH's were required to obtain a decrease of the calcium levels of HMW human protein comparable to that observed with bovine HMW a-crystallin. Investigation of a group of potential calcium-binding compounds indicated that threonine and penicillamine were most effective in reducing the calcium level of HMW human lens protein at neutral pH, removing approximately 58 per cent and 52 per cent, respectively. When the calcium level of bovine HMW a-crystallin was decreased to that found in LMW protein, most of the protein was converted to LMW species. The partial removal of calcium from HMW human lens protein produced a small but significant shift to LMW protein. Deaggregation of human HMW protein under conditions which removed most of the calcium followed by reaggregation in the presence or absence of 5 to 8 mM of calcium indicates that this cation is needed for reaggregation of most of the protein to HMW aggregates. The above observations strongly suggest that calcium is required for the formation of HMW lens protein and that removal of this cation will cause a reversion to LMW species.