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首页> 美国卫生研究院文献>Proceedings of the National Academy of Sciences of the United States of America >Nitrogen Fixation Special Feature: Flavodoxin hydroquinone reduces Azotobacter vinelandii Fe protein to the all-ferrous redox state with a S = 0 spin state
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Nitrogen Fixation Special Feature: Flavodoxin hydroquinone reduces Azotobacter vinelandii Fe protein to the all-ferrous redox state with a S = 0 spin state

机译：固氮特性：Flavodoxin对苯二酚以S = 0的自旋态将藤蔓固氮铁蛋白还原为全铁氧化还原态

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摘要

Azotobacter vinelandii flavodoxin hydroquinone (FldHQ) 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 FldHQ, Ti(III) citrate yields ATP/2e– = 2, and Ti(III)-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 FldHQ 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 for in vivo nitrogenase activity.
机译：葡萄固氮菌黄酮对苯二酚（FldHQ）是一种支持固氮酶的生理还原剂，其能量效率（ATP / 2e – = 2）是连二亚硫酸盐（ATP / 2e – 的两倍） = 4）。与连二亚硫酸盐（仅将Av2还原为[Fe4S4]的连二亚硫酸盐）相比，这种催化效率是由于铁蛋白从铁曲霉（Av2）还原为全铁氧化态（[Fe4S4] 0 ）而产生的。 ] 1 + 状态。像FldHQ一样，柠檬酸Ti（III）产生ATP / 2e – = 2，而Ti（III）还原的[Fe4S4] 0 Av2具有S = 4自旋态，的特征为Mossbauer光谱，并行模式g = 16.4 EPR信号以及其UV-vis光谱在520 nm处的肩峰，每个峰都将S = 4 [Fe4S4] 0 Av2与其他状态区分开。在这项研究中，我们证明FldHQ可以使[Fe4S4] 0 Av2具有足够的特征，以表现出独特的物理性质，从而使其与先前表征的Ti（III）还原的[Fe4S4] 区别开来。 0 Av2。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自旋态（例如[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，类似于[Fe 4 S 4 ] 1 + Av2。 Av2的生理还原剂能够形成[Fe 4 S 4 ] 0 Av2具有重要的意义。

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