Abstract：
Congenital cataract is one of the leading causes of childhood blindness worldwide. About half of heredity cataracts are caused by mutations in various crystallins. However, the underlying mechanisms have not been elucidated for most of crystallin mutations. In this research, we studied the effect of a cataract-causing mutation G75V on γS-crystallin structure, stability and aggregatory propensity. Spectroscopic experiments indicated that the mutation had little impact on γS-crystallin oligomeric status and secondary structure components, but led to large perturbations in tertiary structure. Compared with the WT protein, the G75V mutant had more solvent-accessible Trp fluorophores and hydrophobic exposure. The modified native state of mutant γS-crystallin was more susceptible to environmental stresses such as heat treatment, guanidine hydrochloride and acid conditions. The destabilized mutated protein was more prone to form large aggregates when denatured by high temperature or UV-irradiation. The thermal aggregation of the G75V mutant could be successfully inhibited by excess amount of αA-crystallin with a higher efficiency than the WT protein. Our results suggested that the aberrant modifications in γS-crystallin structure might contribute to the lower stability and higher aggregatory potency of the mutated protein, which subsequently resulted in cataracts in the patients.
摘要：
先天性白内障是全球儿童失明的主要原因之一。大约一半的遗传性白内障是由各种晶状体蛋白的突变引起的。然而,大多数晶状体蛋白突变的潜在机制尚未阐明。在这项研究中,我们研究了引起白内障的突变G75V对γS晶状体蛋白结构的影响，稳定性和聚集倾向。光谱实验表明，突变对γS-晶状蛋白寡聚状态和二级结构组分影响不大，但导致了三级结构的巨大扰动。与WT蛋白相比，G75V突变体具有更多的溶剂可及的Trp荧光团和疏水性暴露。突变体γS-晶状体蛋白的修饰的天然状态更容易受到环境胁迫，例如热处理，盐酸胍和酸性条件。当通过高温或紫外线照射变性时，去稳定的突变蛋白更容易形成大的聚集体。G75V突变体的热聚集可以被过量的αA-晶状体蛋白成功地抑制,其效率高于WT蛋白。我们的结果表明，γS-晶状体蛋白结构的异常修饰可能导致突变蛋白的较低稳定性和较高的聚集效能。随后导致患者白内障。
