Effect of the Electron Density of the Heme Fe Atom on the Nature of Fe-O2 Bonding in Oxy Myoglobin
Effect of the Electron Density of the Heme Fe Atom on the Nature of Fe-O2 Bonding in Oxy Myoglobin
复制标题
血红素 Fe 原子的电子密度对氧合肌红蛋白中 Fe-O2 键性质的影响
DOI：
10.1021/acs.inorgchem.0c03123
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发表时间：
2020
影响因子：
4.6
通讯作者：
Ohta Takehiro
中科院分区：
文献类型：
--
作者：
Yamamoto Yasuhiko;Hasegawa Kazuyasu;Shibata Tomokazu;Momotake Atsuya;Ogura Takashi;Yanagisawa Sachiko;Neya Saburo;Suzuki Akihiro;Kobayashi Yasuhiro;Saito Makina;Seto Makoto;Ohta Takehiro
穆斯堡尔光谱已用于表征用天然和化学改性的富集 57 Fe 血红素辅因子（具有不同血红素 Fe 原子 (ρFe) 电子密度）重构的含氧肌红蛋白 (oxy Mbs)，并阐明 ρFe 变化对血红素 Fe 和氧 (O2) 之间键性质的影响，即 蛋白质中的 Fe-O2 键。发现四极分裂 (ΔEQ) 随着 ρFe 的减小而减小，并且观察到的 ρFe 依赖性 ΔEQ 证实，随着 ρFe 的减小，铁超氧化物 (Fe3+–O2–) 形式对 Fe-O2 片段共振杂化的贡献增加。这些观察结果明确地解释了蛋白质的 O2 亲和力的降低，这是由于 O2 解离速率的增加和氧 Mb 的自氧化反应速率的降低（通过降低结合配体的 H+ 亲和力和 ρFe 的减少）。因此，本研究证明了 O2 亲和力的电子控制和通过血红素电子结构进行蛋白质自氧化的潜在机制。重组 Mbs (CO-Mbs) 的一氧化碳 (CO) 加合物也有类似的特征，我们发现 Fe-CO 片段的两种典型形式之间的共振也受到 ρFe 变化的影响。因此，发现蛋白质中 Fe-配体键的性质受到 ρFe 的影响。
Mössbauer spectroscopy has been used to characterize oxygenated myoglobins (oxy Mbs) reconstituted with native and chemically modified57Fe-enriched heme cofactors with different electron densities of the heme Fe atom (ρFe) and to elucidate the effect of a change in the ρFeon the nature of the bond between heme Fe and oxygen (O2), i.e., the Fe–O2bond, in the protein. Quadrupole splitting (ΔEQ) was found to decrease with decreasing ρFe, and the observed ρFe-dependentΔEQconfirmed an increase in the contribution of the ferric-superoxide (Fe3+–O2–) form to the resonance hybrid of the Fe–O2fragment with decreasing ρFe. These observations explicitly accounted for the lowering of O2affinity of the protein due to an increase in the O2dissociation rate and a decrease in the autoxidation reaction rate of oxy Mb through decreasing H+affinity of the bound ligand with decreasing ρFe. Therefore, the present study demonstrated the mechanism underlying the electronic control of O2affinity and the autoxidation of the protein through the heme electronic structure. Carbon monoxide (CO) adducts of reconstituted Mbs (CO-Mbs) were similarly characterized, and we found that the resonance between the two canonical forms of the Fe–CO fragment was also affected by a change in ρFe. Thus, the nature of the Fe-ligand bond in the protein was found to be affected by the ρFe.