The molecular chaperone αA-crystallin, mainly localized in the human ocular lens, is believed to protect the lens from opacification and cataract, by suppressing the aggregation of the other lens proteins. The present study provides structural and thermodynamic insights into the ability of human αA-crystallin (HAA) to bind to its partially unfolded clients in the lens, using a small peptide, melittin from bee venom, as a model client. We characterized the thermodynamic parameters of the binding process between melittin and HAA through isothermal titration calorimetry (ITC), and found the binding to be endothermic and entropy-driven. We identified the amino acids in melittin important for binding to HAA by saturation-transfer difference (STD) nuclear magnetic resonance (NMR) experiments, and analysis of NMR line broadening upon titration of melittin with HAA. Our results suggest that hydrophobic residues Ile17 and Ile20 on the C-terminal region of melittin are in close contact with HAA in the melittin-HAA complex. Information obtained from NMR experiments was used to generate structural models of the melittin-HAA complex by molecular docking with high-ambiguity driven docking (HADDOCK). Structural models of the melittin-HAA complex reveal important principles underlying the interaction of HAA with its clients.

中文翻译：

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蜂毒肽的疏水残基介导其与 αA-晶状体蛋白的结合。

分子伴侣αA-晶状体蛋白主要位于人眼晶状体中，被认为通过抑制其他晶状体蛋白的聚集来保护晶状体免于混浊和白内障。本研究使用来自蜂毒的蜂毒肽小肽作为模型客户，提供了人类 αA-晶状体蛋白 (HAA) 与晶状体中部分未折叠客户结合的能力的结构和热力学见解。我们通过等温滴定量热法 (ITC) 对蜂毒肽和 HAA 结合过程的热力学参数进行了表征，发现结合是吸热和熵驱动的。我们通过饱和转移差异 (STD) 核磁共振 (NMR) 实验鉴定了蜂毒肽中对结合 HAA 很重要的氨基酸，和分析用 HAA 滴定蜂毒肽时的 NMR 谱线展宽。我们的研究结果表明，蜂毒蛋白 C 末端区域的疏水残基 Ile17 和 Ile20 与蜂毒蛋白-HAA 复合物中的 HAA 密切接触。从 NMR 实验获得的信息用于通过具有高模糊度驱动对接 (HADDOCK) 的分子对接生成蜂毒肽-HAA 复合物的结构模型。蜂毒肽-HAA 复合物的结构模型揭示了 HAA 与其客户互动的重要原理。从 NMR 实验获得的信息用于通过具有高模糊度驱动对接 (HADDOCK) 的分子对接生成蜂毒肽-HAA 复合物的结构模型。蜂毒肽-HAA 复合物的结构模型揭示了 HAA 与其客户互动的重要原理。从 NMR 实验获得的信息用于通过具有高模糊度驱动对接 (HADDOCK) 的分子对接生成蜂毒肽-HAA 复合物的结构模型。蜂毒肽-HAA 复合物的结构模型揭示了 HAA 与其客户互动的重要原理。