Members of the 14-3-3 domain family have important functions as adapter domains. Via an amphipathic groove on their protein surface they typically bind to disordered C-terminals of other proteins. Importantly, binding partners of 14-3-3 domains usually contain a phosphorylated serine or threonine residue at their binding interface and possess one of three different sequence motifs. Binding of the respective unphosphorylated versions of the peptides is typically strongly disfavored. There is a wealth of structural and thermodynamic data available for the phosphorylated forms but not for the unphosphorylated forms as the binding affinities seem to be too weak to be measurable experimentally. Here, we characterized the mechanistic details that govern the preference for the binding of phosphorylated peptides to 14-3-3η domains by means of molecular dynamics (MD) simulations. We found that the phosphate group is ideally coordinated in the binding pocket whereas the respective unphosphorylated side-chain counterpart is not. Thus, the binding preference results from the tight coordination of the phosphorylated residue at the center of the binding interface. Furthermore, MD simulations of 14-3-3η dimers showed a preference for the simultaneous binding of two phosphorylated peptides in agreement with their experimentally observed cooperativity.

中文翻译：

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肽的磷酸化如何影响它们与 14-3-3η 结构域的相互作用

14-3-3 域家族的成员具有作为适配器域的重要功能。通过蛋白质表面的两亲凹槽，它们通常与其他蛋白质的无序 C 末端结合。重要的是，14-3-3 结构域的结合伙伴通常在其结合界面处含有磷酸化的丝氨酸或苏氨酸残基，并具有三种不同的序列基序之一。通常强烈反对肽的各个未磷酸化形式的结合。有大量可用于磷酸化形式的结构和热力学数据，但不适用于未磷酸化形式，因为结合亲和力似乎太弱而无法通过实验测量。在这里，我们描述了控制磷酸化肽与14-3-3结合的偏好的机制细节域通过分子动力学（MD）模拟。我们发现磷酸基团在结合口袋中是理想的配位，而相应的未磷酸化侧链对应物则不是。因此，结合偏好是由结合界面中心的磷酸化残基的紧密配位引起的。此外，14-3-3 η二聚体的 MD 模拟显示两种磷酸化肽同时结合的偏好与其实验观察到的协同性一致。