ABSTRACT Connexins (Cx) are a class of membrane proteins important for auditory function, intercellular signalling and skin biology. Although the presence of concentration of calcium ions is known to work as a trigger for the Cx functionality, the structural changes induced by calcium binding still need to be well elucidated. In this computational study, we have explored the structural effects promoted by Ca2+ on both the wild type (Cx26WT) and on two post-translationally modified Connexin 26 (Cx26): Cx26E42-47γ, which contains two glutamates (E42 and E47) that are γ-carboxylated and Cx26R75m, where a key arginine (R75) is N-monomethylated. These modified amino acids, whose forcefield parameters have been developed in this work, alter Cx26 structure around the Ca2+coordination site. Structural changes were assessed from the analysis of molecular dynamics (MD) simulations. We observed a strict relation between the chemical properties of the post-translational modifications and significantly different responses of Cx26 to Ca2+-binding, while charge-adding modifications have destabilising effects upon calcium coordination, the uncharged ones share the same structural properties of the wild-type counterpart. Overall, these findings suggest the critical role of the electrostatic network flanking the Ca2+ coordination site in maintaining the native tertiary and quaternary structures.

中文翻译：

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野生型和翻译后修饰的 Connexin26 中 Ca2+ 促进的结构效应的建模

摘要 连接蛋白 (Cx) 是一类对听觉功能、细胞间信号传导和皮肤生物学很重要的膜蛋白。尽管已知钙离子浓度的存在可作为 Cx 功能的触发因素，但钙结合引起的结构变化仍需要很好地阐明。在这项计算研究中，我们探索了 Ca2+ 对野生型 (Cx26WT) 和两个翻译后修饰的连接蛋白 26 (Cx26) 的结构影响：Cx26E42-47γ，其中包含两种谷氨酸（E42 和 E47） γ-羧化和 Cx26R75m，其中关键的精氨酸 (R75) 是 N-单甲基化的。这些修饰的氨基酸，其力场参数已在这项工作中开发，改变 Ca2+ 配位位点周围的 Cx26 结构。通过分子动力学 (MD) 模拟分析评估结构变化。我们观察到翻译后修饰的化学性质与 Cx26 对 Ca2+ 结合的显着不同反应之间存在严格关系，而添加电荷的修饰对钙配位具有不稳定影响，不带电荷的修饰具有与野生型相同的结构特性。类型对应。总体而言，这些发现表明位于 Ca2+ 配位点两侧的静电网络在维持原生三级和四级结构中的关键作用。虽然添加电荷的修饰对钙配位具有不稳定影响，但不带电荷的修饰与野生型对应物具有相同的结构特性。总体而言，这些发现表明位于 Ca2+ 配位点两侧的静电网络在维持原生三级和四级结构中的关键作用。虽然添加电荷的修饰对钙配位具有不稳定影响，但不带电荷的修饰与野生型对应物具有相同的结构特性。总体而言，这些发现表明位于 Ca2+ 配位点两侧的静电网络在维持原生三级和四级结构中的关键作用。