Department of Biology, Massachusetts Institute of Technology, Cambridge, MA.
Photochem Photobiol. 2013 Sep-Oct;89(5):1106-15. doi: 10.1111/php.12096. Epub 2013 Jun 20.
Exposure to ultraviolet radiation (UVR) is a significant risk factor for age-related cataract, a disease of the human lens and the most prevalent cause of blindness in the world. Cataract pathology involves protein misfolding and aggregation of the primary proteins of the lens, the crystallins. Human γD-crystallin (HγD-Crys) is a major γ-crystallin in the nucleus of the human lens. We report here analysis of UVR-induced damage to HγD-Crys in vitro. Irradiation of solutions of recombinant HγD-Crys with UVA/UVB light produced a rise in solution turbidity due to polymerization of the monomeric crystallins into higher molecular weight aggregates. A significant fraction of this polymerized protein was covalently linked. Photoaggregation of HγD-Crys required oxygen and its rate was protein concentration and UVR dose dependent. To investigate the potential roles of individual tryptophan residues in photoaggregation, triple W:F mutants of HγD-Crys were irradiated. Surprisingly, despite reducing UVR absorbing capacity, multiple W:F HγD-Crys mutant proteins photoaggregated more quickly and extensively than wild type. The results reported here are consistent with previous studies that postulated that an energy transfer mechanism between the highly conserved pairs of tryptophan residues in HγD-Crys could be protective against UVR-induced photodamage.
紫外线（UVR）暴露是与年龄相关的白内障的一个重要危险因素，这是一种人类晶状体疾病，也是世界上最常见的致盲原因。白内障的病理涉及蛋白质错误折叠和晶状体主要蛋白质的聚集，即晶状体蛋白。人γD-晶体蛋白（HγD-Crys）是人类晶状体核中的主要γ-晶体蛋白。我们在这里报告了体外 UVR 诱导的 HγD-Crys 损伤分析。用 UVA/UVB 光照射重组 HγD-Crys 的溶液会导致单体晶体蛋白聚合形成高分子量聚集体，从而导致溶液浊度升高。这种聚合蛋白的很大一部分是共价连接的。HγD-Crys 的光聚合需要氧气，其速度与蛋白质浓度和 UVR 剂量有关。为了研究单个色氨酸残基在光聚合中的潜在作用，我们照射了 HγD-Crys 的三重 W:F 突变体。令人惊讶的是，尽管减少了 UVR 的吸收能力，但多个 W:F HγD-Crys 突变体蛋白比野生型更快、更广泛地光聚合。这里报道的结果与之前的研究一致，该研究假设 HγD-Crys 中高度保守的色氨酸残基对之间的能量转移机制可能对 UVR 诱导的光损伤具有保护作用。
