Department of Chemistry, University of California, Irvine, CA 92697-2025, USA; Department for Atomically Resolved Dynamics, Max-Planck-Institute for Structure and Dynamics of Matter, Luruper Chaussee 149, 22761 Hamburg, Germany.
Department for Atomically Resolved Dynamics, Max-Planck-Institute for Structure and Dynamics of Matter, Luruper Chaussee 149, 22761 Hamburg, Germany; Institute for Nanostructure and Solid-State Physics, Universität Hamburg, HARBOR, Luruper Chaussee 149, 22761 Hamburg, Germany.
Structure. 2022 May 5;30(5):763-776.e4. doi: 10.1016/j.str.2022.03.002. Epub 2022 Mar 25.
Cataract, a clouding of the eye lens from protein precipitation, affects millions of people every year. The lens proteins, the crystallins, show extensive post-translational modifications (PTMs) in cataractous lenses. The most common PTMs, deamidation and oxidation, promote crystallin aggregation; however, it is not clear precisely how these PTMs contribute to crystallin insolubilization. Here, we report six crystal structures of the lens protein γS-crystallin (γS): one of the wild-type and five of deamidated γS variants, from three to nine deamidation sites, after sample aging. The deamidation mutations do not change the overall fold of γS; however, increasing deamidation leads to accelerated disulfide-bond formation. Addition of deamidated sites progressively destabilized protein structure, and the deamidated variants display an increased propensity for aggregation. These results suggest that the deamidated variants are useful as models for accelerated aging; the structural changes observed provide support for redox activity of γS-crystallin in the lens.
白内障是一种由蛋白质沉淀引起的眼晶状体混浊，每年影响数百万人。晶状体蛋白，即晶体蛋白，在白内障晶状体中表现出广泛的翻译后修饰（PTM）。最常见的 PTM，脱酰胺和氧化，促进晶体蛋白聚集；然而，这些 PTM 如何导致晶体蛋白不溶尚不清楚。在这里，我们报告了六种晶状体蛋白 γS-晶体蛋白（γS）的晶体结构：一个野生型和五个脱酰胺的 γS 变体，在样品老化后，有三个到九个脱酰胺位点。脱酰胺突变不会改变 γS 的整体折叠；然而，增加脱酰胺会导致二硫键形成加速。添加脱酰胺位点逐渐破坏蛋白质结构，脱酰胺变体显示出更高的聚集倾向。这些结果表明，脱酰胺变体可用作加速老化的模型；观察到的结构变化为晶状体中 γS-晶体蛋白的氧化还原活性提供了支持。
