Mutation R120G in αB-crystallin, which is linked to a desmin-related myopathy, results in an irregular structure and defective chaperone-like function
Mutation R120G in αB-crystallin, which is linked to a desmin-related myopathy, results in an irregular structure and defective chaperone-like function
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DOI：
10.1073/pnas.96.11.6137
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发表时间：
1999-05-25
影响因子：
11.1
通讯作者：
Horwitz, J
中科院分区：
文献类型：
--
作者：
Bova, MP;Yaron, O;Horwitz, J
α B-晶状体蛋白是小热休克蛋白家族的成员，具有类似伴侣的功能。最近，已表明 α B-晶状体蛋白 R120G 中的错义突变与结蛋白相关肌病以及白内障有遗传相关性 [Vicart, P.、Caron, A.、Guicheney, P.、Li, A.、Prevost, M.-C.、Faure, A.、Chateau, D.、Chapon, F.、Tome, P.、Dupret, J.-M.等人。 (1998) 不是。热内特. 20、92-95]。通过使用α-乳清蛋白、乙醇脱氢酶和胰岛素作为靶蛋白，体外测定表明R120G αB-晶状体蛋白降低或完全丧失了伴侣样功能。在未折叠的 α-乳清蛋白中添加 R120G α B-晶状体蛋白增强了其聚集的动力学和程度。 R120G α B-晶状体蛋白与展开的α-乳清蛋白纠缠在一起，并且是所得不溶性沉淀的主要部分。类似地，R120G α B-晶状体蛋白与乙醇脱氢酶和胰岛素一起温育也导致不溶性沉淀中存在R120G α B-晶状体蛋白。远紫外和近紫外 CD 表明，与野生型 α B 晶状体蛋白相比，R120G α B 晶状体蛋白具有减少的 β 折叠二级结构和改变的芳香族残基环境。通过凝胶过滤色谱测定，R120G α B-晶状体蛋白的表观分子量为 1.4 MDa，是野生型 α B-晶状体蛋白 (650 kDa) 分子量的两倍多。从冷冻电子显微镜获得的图像表明，R120G α B-晶状体蛋白具有不规则的四级结构，没有清晰的中央空腔。这项研究的结果通过生化分析表明，α B-晶状体蛋白的结构改变和伴侣样功能缺陷与导致结蛋白相关肌病和白内障的点突变有关。
alpha B-crystallin, a member of the small heat shock protein family, possesses chaperone-like function. Recently, it has been shown that a missense mutation in alpha B-crystallin, R120G, is genetically linked to a desmin-related myopathy as well as to cataracts [Vicart, P., Caron, A., Guicheney, P., Li, A., Prevost, M.-C., Faure, A., Chateau, D., Chapon, F., Tome, P., Dupret, J.-M., et al. (1998) Not. Genet. 20, 92-95]. By using alpha-lactalbumin, alcohol dehydrogenase, and insulin as target proteins, in vitro assays indicated that R120G alpha B-crystallin had reduced or completely lost chaperone-like function. The addition of R120G alpha B-crystallin to unfolding alpha-lactalbumin enhanced the kinetics and extent of its aggregation. R120G alpha B-crystallin became entangled with unfolding alpha-lactalbumin and was a major portion of the resulting insoluble pellet. Similarly, incubation of R120G alpha B-crystallin with alcohol dehydrogenase and insulin also resulted in the presence of R120G alpha B-crystallin in the insoluble pellets. Far and near UV CD indicate that R120G alpha B-crystallin has decreased beta-sheet secondary structure and an altered aromatic residue environment compared with wild-type alpha B-crystallin. The apparent molecular mass of R120G alpha B-crystallin, as determined by gel filtration chromatography, is 1.4 MDa, which is more than twice the molecular mass of wild-type alpha B-crystallin (650 kDa). Images obtained from cryoelectron microscopy indicate that R120G alpha B-crystallin possesses an irregular quaternary structure with an absence of a clear central cavity. The results of this study show, through biochemical analysis, that an altered structure and defective chaperone-like function of alpha B-crystallin are associated with a point mutation that leads to a desmin-related myopathy and cataracts.