Abstract：
Human γD-crystallin belongs to a crucial family of proteins known as crystallins located in the fiber cells of the human lens. Since crystallins do not undergo any turnover after birth, they need to possess remarkable thermodynamic stability. However, their sporadic misfolding and aggregation, triggered by environmental perturbations or genetic mutations, constitute the molecular basis of cataracts, which is the primary cause of blindness in the globe according to the World Health Organization. Here, we investigate the impact of high pressure on the conformational landscape of wild-type HγD-crystallin using replica exchange molecular dynamics simulations augmented with principal component analysis. We find pressure to have a modest impact on global measures of protein stability, such as root-mean-square displacement and radius of gyration. Upon projecting our trajectories along the first two principal components from principal component analysis, however, we observe the emergence of distinct free energy basins at high pressures. By screening local order parameters previously shown or hypothesized as markers of HγD-crystallin stability, we establish correlations between a tyrosine-tyrosine aromatic contact within the N-terminal domain and the protein\'s end-to-end distance with projections along the first and second principal components, respectively. Furthermore, we observe the simultaneous contraction of the hydrophobic core and its intrusion by water molecules. This exploration sheds light on the intricate responses of HγD-crystallin to elevated pressures, offering insights into potential mechanisms underlying its stability and susceptibility to environmental perturbations, crucial for understanding cataract formation.
摘要：
人γD-晶状体蛋白属于位于人晶状体的纤维细胞中的称为晶状体蛋白的关键蛋白质家族。由于晶体蛋白在出生后不会发生任何周转，它们需要具有显著的热力学稳定性。然而,它们零星的错误折叠和聚集，由环境扰动或基因突变引发，构成白内障的分子基础，根据世界卫生组织，这是全球失明的主要原因。这里,我们研究了高压对野生型HγD晶状体蛋白构象景观的影响，使用复制交换分子动力学模拟增强主成分分析。我们发现压力对全球蛋白质稳定性指标产生适度影响，例如均方根位移和回转半径。通过主成分分析，沿着前两个主成分预测我们的轨迹，然而,我们观察到在高压下出现了不同的自由能盆地。通过筛选先前显示或假设为HγD-晶状体蛋白稳定性标志物的局部有序参数，我们建立了N端结构域内的酪氨酸-酪氨酸芳香接触与蛋白质的端到端距离之间的相关性，以及沿第一和第二主成分的投影，分别。此外，我们观察到疏水核的同时收缩及其被水分子的侵入。这项探索揭示了HγD-晶状体蛋白对高压的复杂反应，提供对其稳定性和对环境扰动敏感性的潜在机制的见解，对于理解白内障的形成至关重要。
