Weak O2 binding and strong H2O2 binding at the non-heme diiron center of Trypanosome Alternative Oxidase
Weak O2 binding and strong H2O2 binding at the non-heme diiron center of Trypanosome Alternative Oxidase
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锥虫替代氧化酶非血红素二铁中心的弱 O2 结合和强 H2O2 结合
DOI：
10.1016/j.bbabio.2020.148356
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
Y.Shigeta
中科院分区：
文献类型：
--
作者：
S.Yamasaki;M.Shoji;M.Kayanuma;V.Sladek;D.K.Inaoka;Y.Matsuo;T.Shiba;L.Young;A.L.Moore;K.Kita;Y.Shigeta
替代氧化酶（AOX）作为附加的末端氧化酶催化双氧的四电子还原成水，催化反应对寄生虫在其血流形式中存活至关重要。最近，报道了锥虫选择性氧化酶（TAO）与阿魏烯醇络合的x射线晶体结构，并测定了非血红素二铁中心的分子结构。与其他铁蛋白相比，o2的结合是一种独特的on型。为了表征TAO的o2结合态，本研究在量子力学/分子力学（QM/MM）理论水平上对o2结合态进行了搜索。我们发现最稳定的o2结合态是端上型，而侧上型的结合态能量更高。根据结合能和电子结构分析，o2与TAO铁中心的结合非常弱（ΔE=6.7 kcal mol−1），处于Fe（II）…o双键do的电子态，而不是像甲氰氰酯那样处于超氧化物态（Fe（III）单键do·-）的电荷转移态。其他配体如水、Cl−、CN−、CO、N3−和h2o2的配位也进行了研究，发现h2o2与Fe（II）位点的结合最强byΔE= 14.0 kcal mol−1。通过测定TAO和细小隐孢子虫的泛醇氧化酶活性，实验证实了这一点，发现h2o2对TAO和细小隐孢子虫的泛醇氧化酶活性具有剂量依赖性和可逆的抑制作用。
Alternative oxidase (AOX) catalyzes the four-electron reduction of dioxygen to water as an additional terminal oxidase, and the catalytic reaction is critical for the parasite to survive in its bloodstream form. Recently, the X-ray crystal structure of trypanosome alternative oxidase (TAO) complexed with ferulenol was reported and the molecular structure of the non-heme diiron center was determined. The binding of O2was a uniqueside-ontype compared to other iron proteins. In order to characterize the O2binding state of TAO, the O2binding states were searched at a quantum mechanics/molecular mechanics (QM/MM) theoretical level in the present study. We found that the most stable O2binding state is theend-ontype, and the binding states of theside-ontype are higher in energy. Based on the binding energies and electronic structure analyses, O2binds very weakly to the TAO iron center (ΔE=6.7 kcal mol−1) in the electronic state of Fe(II)…Odouble bondO, not in the suggested charge transferred state such as the superoxide state (Fe(III)single bondOsingle bondO·–) as seen in hemerythrin. Coordination of other ligands such as water, Cl−, CN−, CO, N3−and H2O2was also examined, and H2O2was found to bind most strongly to the Fe(II) site byΔE= 14.0 kcal mol−1. This was confirmed experimentally through the measurement of ubiquinol oxidase activity of TAO andCryptosporidium parvumAOX which was found to be inhibited by H2O2in a dose-dependent and reversible manner.