Substitution of Ca<sup>2+</sup> and changes in the H-bond network near the oxygen-evolving complex of photosystem II
Substitution of Ca<sup>2+</sup> and changes in the H-bond network near the oxygen-evolving complex of photosystem II
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Ca<sup>2</sup> 的取代和光系统 II 放氧复合物附近氢键网络的变化
DOI：
10.1039/d2cp05036f
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发表时间：
2023
影响因子：
3.3
通讯作者：
Ishikita Hiroshi
中科院分区：
文献类型：
--
作者：
Mandal Manoj;Saito Keisuke;Ishikita Hiroshi
Ca 2+为Mn 4CaO 5团簇中的配体水分子W3和W 4提供结合位点，是光系统II（PSII）释放O2的先决条件。我们报告的氢键网络和催化簇本身的结构变化后，更换的Ca 2+与其他碱土金属，使用量子力学/分子力学方法。在Mg 2+-PSII体系中，由于Mg 2+半径小，使W3与D1-Glu 189形成氢键。如果一个额外的水分子结合在Ba 2+的大表面上，它会给D1-Glu 189和悬挂Mn上的配体水分子提供氢键，从而改变氢键网络。D1-Tyr 161（TyrZ）和D1-His 190之间的氢键势能分布以及开闭立方烷S2构象之间的相互转换在Ca 2+置换后基本保持不变。值得注意的是，在所有的O 5-金属距离中，O 5-Ca 2+距离是最短的，而与半径大于Mg 2+的半径无关。此外，Ca 2+是唯一的碱土金属，平衡的O 5金属和O2金属的距离，并促进对称立方烷结构的形成。
Ca 2+, which provides binding sites for ligand water molecules W3 and W4 in the Mn 4 CaO 5 cluster, is a prerequisite for O 2 evolution in photosystem II (PSII). We report structural changes in the H-bond network and the catalytic cluster itself upon the replacement of Ca 2+ with other alkaline earth metals, using a quantum mechanical/molecular mechanical approach. The small radius of Mg 2+ makes W3 donate an H-bond to D1-Glu189 in Mg 2+-PSII. If an additional water molecule binds at the large surface of Ba 2+, it donates H-bonds to D1-Glu189 and the ligand water molecule at the dangling Mn, altering the H-bond network. The potential energy profiles of the H-bond between D1-Tyr161 (TyrZ) and D1-His190 and the interconversion between the open-and closed-cubane S 2 conformations remain substantially unaltered upon the replacement of Ca 2+. Remarkably, the O5⋯ Ca 2+ distance is shortest among all O5⋯ metal distances irrespective of the radius being larger than that of Mg 2+. Furthermore, Ca 2+ is the only alkaline earth metal that equalizes the O5⋯ metal and O2⋯ metal distances and facilitates the formation of the symmetric cubane structure.