Available high‐resolution crystal structures for the family of β‐trefoil proteins in the structural databank were queried for buried waters. Such waters were classified as either: (a) unique to a particular domain, family, or superfamily or (b) conserved among all β‐trefoil folds. Three buried waters conserved among all β‐trefoil folds were identified. These waters are related by the threefold rotational pseudosymmetry characteristic of this protein architecture (representing three instances of an identical structural environment within each repeating trefoil‐fold motif). The structural properties of this buried water are remarkable and include: residing in a cavity space no larger than a single water molecule, exhibiting a positional uncertainty (i.e., normalized B‐factor) substantially lower than the average Cα atom, providing essentially ideal H‐bonding geometry with three solvent‐inaccessible main chain groups, simultaneously serving as a bridging H‐bond for three different β‐strands at a point of secondary structure divergence, and orienting conserved hydrophobic side chains to form a nascent core‐packing group. Other published work supports an interpretation that these interactions are key to the formation of an efficient folding nucleus and folded thermostability. The fundamental threefold symmetric structural element of the β‐trefoil fold is therefore, surprisingly, a buried water molecule.

中文翻译：

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保守的埋藏水分子使β-三叶形结构成为可能。

查询结构数据库中 β-三叶蛋白家族的可用高分辨率晶体结构以寻找埋藏水域。这些水域被分类为：（a）特定域、家族或超家族所独有的，或（b）在所有 β-三叶折叠中保守的。确定了所有 β-三叶褶皱中保存的三个埋藏水域。这些水与这种蛋白质结构的三重旋转假对称特征有关（代表每个重复三叶折叠基序内相同结构环境的三个实例）。这种埋藏水的结构特性非常显着，包括：位于不大于单个水分子的空腔空间中，表现出明显低于平均 Cα 原子的位置不确定性（即归一化 B 因子），提供具有三个溶剂不可接近的主链基团的基本理想的 H 键几何结构，同时在二级结构发散点处充当三个不同 β 链的桥接 H 键，并将保守的疏水侧链定向以形成新生的核心包装组。其他已发表的工作支持这样一种解释，即这些相互作用是形成有效折叠核和折叠热稳定性的关键。因此，令人惊讶的是，β-三叶折叠的基本三重对称结构元素是一个隐藏的水分子。并将保守的疏水侧链定向以形成新生的核心填充基团。其他已发表的工作支持这样一种解释，即这些相互作用是形成有效折叠核和折叠热稳定性的关键。因此，令人惊讶的是，β-三叶折叠的基本三重对称结构元素是一个隐藏的水分子。并将保守的疏水侧链定向以形成新生的核心填充基团。其他已发表的工作支持这样一种解释，即这些相互作用是形成有效折叠核和折叠热稳定性的关键。因此，令人惊讶的是，β-三叶折叠的基本三重对称结构元素是一个隐藏的水分子。