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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Flavodoxin hydroquinone reduces Azotobacter vinelandii Fe protein to the all-ferrous redox state with a S=0 spin state
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Flavodoxin hydroquinone reduces Azotobacter vinelandii Fe protein to the all-ferrous redox state with a S=0 spin state

机译：Flavodoxin对苯二酚将Sazotobacter vinelandii Fe蛋白还原为全铁氧化还原态（S = 0旋态）

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摘要

Azotobacter vinelandii flavodoxin hydroquinone (FIdHQ) is a physiological reductant to nitrogenase supporting catalysis that is twice as energy efficient (ATP/2e(-) = 2) as dithionite (ATP/2e- = 4). This catalytic efficiency results from reduction of Fe protein from A. vinelandii (Av2) to the all-ferrous oxidation state ([Fe4S4](0)), in contrast to dithionite, which only reduces Av2. to the [Fe4S4](1+) state. Like FIdHQ, Ti(III) citrate yields ATIP/2e(-) = 2, and Ti(Ill)reduced [Fe4S4](0) Av2 has a S = 4 spin state and characteristic Mossbauer spectrum, a parallel mode g = 16.4 EPR signal, and a shoulder at 520 nm in its UV-vis spectrum, each of which distinguish the S = 4 [Fe4S4](0) Av2 from other states. In this study, we demonstrate that FIdHQ makes [Fe4S4](0) Av2, which is sufficiently characterized to demonstrate unique physical properties that distinguish it from the previously characterized Ti(III)-reduced [Fe4S4](0) Av2. In particular, Evans NMR magnetic susceptibility and EPR measurements indicate that FldHQ-reduced [Fe4S4](0) Av2 has an S = 0 spin state (like [Fe4S4](2+) Av2). There is no g = 16.4 EPR signal and no shoulder at 520 nm in its absorbance spectrum, which resembles that of [Fe4S4](1+) Av2. That the physiological reductant to Av2 is capable of forming [Fe4S4](0) Av2 has important implications or in vivo nitrogenase activity.
机译：葡萄固氮菌黄酮毒素氢醌（FIdHQ）是一种支持固氮酶催化的生理还原剂，其能量效率（ATP / 2e（-）= 2）是连二亚硫酸盐（ATP / 2e- = 4）的两倍。与连二亚硫酸盐仅还原Av2的连二亚硫酸盐相反，该催化效率是由铁蛋白从藤蔓A. vinelandii（Av2）还原为全亚铁氧化态（[Fe4S4]（0））产生的。到[Fe4S4]（1+）状态。像FIdHQ一样，柠檬酸Ti（III）的ATIP / 2e（-）= 2，Ti（III）还原的[Fe4S4]（0）Av2具有S = 4的自旋态和特征性的Mossbauer光谱，平行模g = 16.4 EPR信号，以及在520 nm的UV-vis光谱中的肩部，每个都将S = 4 [Fe4S4]（0）Av2与其他状态区分开。在这项研究中，我们证明FIdHQ可以制造[Fe4S4]（0）Av2，它的特征足以证明其独特的物理性质，使其与先前表征的Ti（III）还原的[Fe4S4]（0）Av2区别开来。尤其是，Evans NMR磁化率和EPR测量表明FldHQ还原的[Fe4S4]（0）Av2具有S = 0的自旋态（类似于[Fe4S4]（2+）Av2）。在其吸收光谱中没有g = 16.4 EPR信号，并且在520 nm处没有肩峰，这与[Fe4S4]（1+）Av2相似。 Av2的生理还原剂能够形成[Fe4S4]（0）Av2具有重要的意义或体内的固氮酶活性。

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