The Human W42R γD-Crystallin Mutant Structure Provides a Link between Congenital and Age-related Cataracts
The Human W42R γD-Crystallin Mutant Structure Provides a Link between Congenital and Age-related Cataracts
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DOI：
10.1074/jbc.m112.416354
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发表时间：
2013-01-04
影响因子：
4.8
通讯作者：
Gronenborn, Angela M.
中科院分区：
文献类型：
--
作者：
Ji, Fangling;Jung, Jinwon;Gronenborn, Angela M.
人类γ-D-晶体蛋白的一些突变与先天性白内障密切相关，尽管突变相关的白内障形成的详细分子机制通常尚不清楚。在这里，我们报告了最近发现的一个与常染色体显性遗传性先天性白内障有关的伽马D-晶体蛋白突变体(W42R)。与野生型伽马D-晶体蛋白相比，突变蛋白的溶解性和稳定性要差得多。我们在1.7埃分辨率下求解了W42R的晶体结构，这与野生型结构只有很小的差别。有趣的是，W42R变异体非常容易被蛋白酶消化，这表明存在一小部分未折叠的蛋白质。核磁共振波谱对这种部分展开的物种进行了确认和定量。氢/氢交换实验揭示了折叠和未折叠物种之间的化学交换。野生型伽马D-晶体蛋白暴露在紫外线下会对蛋白质的N-末端结构域造成损害，导致与W42R突变体非常相似的蛋白降解敏感性。总之，我们的联合数据使我们能够提出一个W42R发病机制的模型，W42R突变体可以模拟年龄相关性白内障中涉及的光损伤的伽马D-晶体蛋白。
Some mutants of human gamma D-crystallin are closely linked to congenital cataracts, although the detailed molecular mechanisms of mutant-associated cataract formation are generally not known. Here we report on a recently discovered gamma D-crystallin mutant (W42R) that has been linked to autosomal dominant, congenital cataracts in a Chinese family. The mutant protein is much less soluble and stable than wild-type gamma D-crystallin. We solved the crystal structure of W42R at 1.7 angstrom resolution, which revealed only minor differences from the wild-type structure. Interestingly, the W42R variant is highly susceptible to protease digestion, suggesting the presence of a small population of partially unfolded protein. This partially unfolded species was confirmed and quantified by NMR spectroscopy. Hydrogen/deuterium exchange experiments revealed chemical exchange between the folded and unfolded species. Exposure of wild-type gamma D-crystallin to UV caused damage to the N-terminal domain of the protein, resulting in very similar proteolytic susceptibility as observed for the W42R mutant. Altogether, our combined data allowed us to propose a model for W42R pathogenesis, with the W42R mutant serving as a mimic for photodamaged gamma D-crystallin involved in age-related cataract.