Energetics of oxidized and reduced methane monooxygenase active site clusters in the protein environment.
Energetics of oxidized and reduced methane monooxygenase active site clusters in the protein environment.
复制标题
蛋白质环境中氧化和还原甲烷单加氧酶活性位点簇的能量学。
DOI：
10.1021/ic010116b
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发表时间：
2001
影响因子：
4.6
通讯作者：
Noodleman,L
中科院分区：
文献类型：
--
作者：
Lovell,T;Li,J;Noodleman,L
使用随附论文（Lovell, T.; Li, J.; Noodleman, L.Inorg.Chem.2001,40, 5251）中获得的密度泛函优化活性位点几何形状，应用密度泛函和静电相结合的方法来进一步解决 MMOHox 桥配体质子化状态中伴随的不确定性。与荚膜甲基球菌中桥接 H2O 配体相关的酸度 (pKas) 以及与蛋白质环境相互作用的每个活性位点簇的相应能量学已得到评估。 pKa 计算与气相 DFT 研究结果相结合，使得甲基窦丝孢子菌中的活性位点簇可以最好地描述为由具有总体中性净簇电荷的 2OH-配体桥接的二铁单元。外源乙酸盐的存在以M计。 capsulatus 揭示了一个由 1OH- 和 1H2O 桥接的二铁单元，该二铁单元在非常短的强 AcO··H·OH 氢键中与第二壳乙酸酯不对称地共享其质子。对于所有检查的 MMOHox 和 MMOH 还原位点，从 ESP 原子电荷可以明显看出显着的 Fe−配体共价性，这与来自 μOH 和 μ-羧基桥配体的非常强的配体 → 金属电荷转移一致。活性结构域中各个蛋白质残基与活性位点的静电相互作用的大小已通过能量分解方案进行了评估。重要的第二壳残基被强调用于下一阶段基于量子力学的计算或用于定点诱变研究。最后，根据已知的结构和光谱证据以及 DFT 研究，提出了将 MMOHoxin 转化为 MMOHred 的可能机制，该机制涉及蛋白质残基和来自第二配位层的溶剂衍生配体的组合。
Using the density functional optimized active site geometries obtained in the accompanying paper (Lovell, T.; Li, J.; Noodleman, L.Inorg.Chem.2001,40, 5251), a combined density functional and electrostatics approach has been applied to further address attendant uncertainties in the protonation states of the bridging ligands for MMOHox. The acidities (pKas) associated with the bridging H2O ligand inMethylococcus capsulatusand corresponding energetics of each active site cluster interacting with the protein environment have been evaluated. The pKacalculations in combination with the results of the gas phase DFT studies allow the active site cluster inMethylosinustrichosporiumto be best described as a diiron unit bridged by 2OH-ligands having an overall neutral net cluster charge. The presence of the exogenous acetate inM. capsulatusreveals a diiron unit bridged by 1OH-and 1H2O which asymmetrically shares its proton with a second-shell acetate in a very short strong AcO··H···OH hydrogen bond. For all MMOHoxand MMOHredactive sites examined, significant Fe−ligand covalency is evident from the ESP atom charges, consistent with very strong ligand → metal charge transfer from the μOH-and μ-carboxylato bridging ligands. The magnitude of electrostatic interaction of the individual protein residues in the active domain with the active site has been assessed via an energy decomposition scheme. Important second-shell residues are highlighted for the next level of quantum mechanics based calculations or alternatively for site-directed mutagenesis studies. Finally, from the known structural and spectroscopic evidence and the DFT studies, a possible mechanism is suggested for the conversion of MMOHoxinto MMOHredthat involves a combination of protein residues and solvent-derived ligands from the second coordination sphere.