Dioxygen and glucose force motion of the electron-transfer switch in the iron(III) flavohemoglobin-type nitric oxide dioxygenase.
Dioxygen and glucose force motion of the electron-transfer switch in the iron(III) flavohemoglobin-type nitric oxide dioxygenase.
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DOI：
10.1016/j.jinorgbio.2023.112257
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发表时间：
2023-05
影响因子：
3.9
通讯作者：
A. Gardner;P. R. Gardner
中科院分区：
文献类型：
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作者：
A. Gardner;P. R. Gardner
黄血红蛋白型NO双加氧酶的动力学和结构研究表明，它在瞬时Fe(III) o2络合物形成和o2强迫运动中起关键作用，影响氢化物向FAD辅因子的转移和电子向Fe(III) o2络合物的转移。stark效应理论、结构模型、偶极子和内部静电场测定为研究所提出的Fe(III) o2配合物和o2强迫运动提供了半定量光谱方法。酶的脱氧对铁血红素Soret和显示Fe(III) o2络合物的电荷转移带产生斯塔克效应。脱氧还会对FAD产生斯塔克效应，暴露出作用力和运动，从而使NADH进入FAD进行氢化物转移并关闭电子转移。葡萄糖也迫使酶进入关闭状态。氨基酸在B10、E7、E11、G8、D5和F7位置的取代影响了o2对静息血红素自旋态和FAD的Stark效应，这与侧链在酶机制中的作用一致。铁肌红蛋白和血红蛋白A的脱氧也会对血红素产生斯塔克效应，这表明血红素处于一种常见的“氧合”状态。铁肌红蛋白和血红蛋白血红素谱也对葡萄糖有反应。在黄血红蛋白和肌红蛋白的bc角和g -螺旋之间发现了一个保守的葡萄糖或葡萄糖-6-磷酸结合位点，这表明葡萄糖或葡萄糖-6-磷酸在一氧化氮双加氧酶和氧储存功能中起着新的变构效应作用。研究结果支持了一氧化氮双加氧酶转换过程中二氧化铁中间体和蛋白质运动在调节电子转移中的作用。
Kinetic and structural investigations of the flavohemoglobin-type NO dioxygenase have suggested critical roles for transient Fe(III)O2complex formation and O2-forced movements affecting hydride transfer to the FAD cofactor and electron-transfer to the Fe(III)O2complex. Stark-effect theory together with structural models and dipole and internal electrostatic field determinations provided a semi-quantitative spectroscopic method for investigating the proposed Fe(III)O2complex and O2-forced movements. Deoxygenation of the enzyme causes Stark effects on the ferric heme Soret and charge-transfer bands revealing the Fe(III)O2complex. Deoxygenation also elicits Stark effects on the FAD that expose forces and motions that create a more restricted NADH access to FAD for hydride transfer and switch electron-transfer off. Glucose also forces the enzyme toward an off state. Amino acid substitutions at the B10, E7, E11, G8, D5, and F7 positions influence the Stark effects of O2on resting heme spin states and FAD consistent with the proposed roles of the side chains in the enzyme mechanism. Deoxygenation of ferric myoglobin and hemoglobin A also induces Stark effects on the hemes suggesting a common ‘oxy-met’ state. The ferric myoglobin and hemoglobin heme spectra are also glucose-responsive. A conserved glucose or glucose-6-phosphate binding site is found bridging the BC-corner and G-helix in flavohemoglobin and myoglobin suggesting novel allosteric effector roles for glucose or glucose-6-phosphate in the NO dioxygenase and O2storage functions. The results support the proposed roles of a ferric O2intermediate and protein motions in regulating electron-transfer during NO dioxygenase turnover.