Nikolaieva Yuliia, Chaproniere Laurel
Nottingham Trent University.
Res Sq. 2025 Aug 29:rs.3.rs-7408454. doi: 10.21203/rs.3.rs-7408454/v1.
The T138R mutation in Aquaporin 0 (AQP0), a key membrane protein in the ocular lens, causes autosomal dominant congenital cataracts. Whilst previous studies have demonstrated that this mutation disrupts water permeability and leads to protein mislocalisation, the specific structural mechanisms underlying these functional defects remain unclear. This study employed in silico approaches to characterise how the T138R substitution affects AQP0's molecular structure and stability. Computational analysis revealed that whilst the mutation does not significantly alter the protein's global conformation (RMSD = 0.000 Å), it may disrupt a key network of hydrogen bonds involving Glu134, Ile135, and Pro208. Multiple sequence alignment showed these interacting residues are highly conserved across species, underscoring their structural or functional importance. Hydrophobicity analysis indicated that the substitution resulted in a strongly hydrophilic, positively charged residue (Arg, Kyte-Doolittle score: -4.5) into a predominantly hydrophobic transmembrane environment. Transmembrane insertion energetics calculations demonstrated a possible increase for membrane integration (ΔGpredapp: +1.42 to + 1.63 kcal/mol), with the Arg side chain contributing nearly twice the insertion cost of Thr (+ 0.23 vs. +0.41 kcal/mol). Protein-protein interaction modelling with Connexin 50 revealed subtle but potentially significant changes at the docking interface, including potential decreased solvent-excluded surface (-0.00019646) and increased solvent-accessible surface (+ 0.00062829) changes. Additionally, potential steric clashes between Arg138 and Met183 were identified. These findings suggested reduced compactness, possible formation of internal voids and disruption of local packing. This work provided insight into the structural changes that may underlie the functional impairments of AQP0, supporting future research into its role in cataract formation.
水通道蛋白0（AQP0）是晶状体中的一种关键膜蛋白，其T138R突变会导致常染色体显性遗传性先天性白内障。虽然先前的研究表明这种突变会破坏水通透性并导致蛋白质错误定位，但这些功能缺陷背后的具体结构机制仍不清楚。本研究采用计算机模拟方法来表征T138R取代如何影响AQP0的分子结构和稳定性。计算分析表明，虽然该突变不会显著改变蛋白质的整体构象（均方根偏差=0.000 Å），但它可能会破坏涉及Glu134、Ile135和Pro208的关键氢键网络。多序列比对显示，这些相互作用的残基在物种间高度保守，强调了它们在结构或功能上的重要性。疏水性分析表明，该取代导致一个强亲水性、带正电荷的残基（精氨酸，凯泰-杜利特尔评分：-4.5）进入一个主要为疏水性的跨膜环境。跨膜插入能计算表明膜整合可能增加（预测的自由能变化：+1.42至+1.63千卡/摩尔），精氨酸侧链对插入成本的贡献几乎是苏氨酸的两倍（+0.23对+0.41千卡/摩尔）。与连接蛋白50的蛋白质-蛋白质相互作用建模显示对接界面处有细微但可能显著的变化，包括潜在的溶剂排除表面积减小（-0.00019646）和溶剂可及表面积增加（+0.00062829）变化。此外，还发现了精氨酸138和甲硫氨酸183之间可能的空间冲突。这些发现表明结构紧凑性降低、可能形成内部空隙以及局部堆积破坏。这项工作为AQP0功能受损可能的结构变化提供了见解，支持了未来对其在白内障形成中作用的研究。
