与固氮酶催化相关的 Fe 蛋白质循环需要为每个单电子转移事件水解两个 ATP,Journal of the American Chemical Society

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与固氮酶催化相关的 Fe 蛋白质循环需要为每个单电子转移事件水解两个 ATP
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2023-03-01 , DOI: 10.1021/jacs.2c09576
Zhi-Yong Yang ₁ , Artavazd Badalyan ₁ , Brian M Hoffman ₂ , Dennis R Dean ₃ , Lance C Seefeldt ₁

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目前对通过固氮酶还原二氮 (N 2 ) 的理解的一个核心特征是建议将两个 ATP 的水解偶联，形成两个 ADP 和两个 Pi，以将一个电子从 Fe 蛋白质组分转移_到MoFe蛋白质成分，底物减少。与 Fe 蛋白相关的氧化还原活性 [4Fe-4S] 簇是电子传递的代理，众所周知，它具有在单电子还原的 [4Fe-4S] 1+ 状态和单电子还原状态之间循环^的能力氧化的 [4Fe-4S] ²⁺态。然而，最近已经表明，可以使用某些还原剂将 Fe 蛋白 [4Fe-4S] 簇进一步还原为超还原的全铁 [4Fe-4S] ⁰状态可以是抗磁的（S = 0）或顺磁的（S = 4）。有人提出，超还原状态可能从根本上改变固氮酶能量利用的现有模型，每个 Fe 蛋白质循环转移两个电子，与仅两个 ATP 分子的水解有关。^{在这里，我们测量了当 Fe 蛋白簇处于 [4Fe-4S] 1+}状态和处于 [4Fe-4S] ⁰状态时，在稳态催化下每次电子转移消耗的 ATP 数量状态。发现 Fe 蛋白的两种氧化态都通过为每个单电子转移事件水解两个 ATP 来运作。因此，无论其初始氧化还原状态如何，Fe 蛋白在需要水解两个 ATP 的过程中一次仅将一个电子转移到 MoFe 蛋白。

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The Fe Protein Cycle Associated with Nitrogenase Catalysis Requires the Hydrolysis of Two ATP for Each Single Electron Transfer Event

A central feature of the current understanding of dinitrogen (N₂) reduction by the enzyme nitrogenase is the proposed coupling of the hydrolysis of two ATP, forming two ADP and two Pi, to the transfer of one electron from the Fe protein component to the MoFe protein component, where substrates are reduced. A redox-active [4Fe-4S] cluster associated with the Fe protein is the agent of electron delivery, and it is well known to have a capacity to cycle between a one-electron-reduced [4Fe-4S]¹⁺ state and an oxidized [4Fe-4S]²⁺ state. Recently, however, it has been shown that certain reducing agents can be used to further reduce the Fe protein [4Fe-4S] cluster to a super-reduced, all-ferrous [4Fe-4S]⁰ state that can be either diamagnetic (S = 0) or paramagnetic (S = 4). It has been proposed that the super-reduced state might fundamentally alter the existing model for nitrogenase energy utilization by the transfer of two electrons per Fe protein cycle linked to hydrolysis of only two ATP molecules. Here, we measure the number of ATP consumed for each electron transfer under steady-state catalysis while the Fe protein cluster is in the [4Fe-4S]¹⁺ state and when it is in the [4Fe-4S]⁰ state. Both oxidation states of the Fe protein are found to operate by hydrolyzing two ATP for each single-electron transfer event. Thus, regardless of its initial redox state, the Fe protein transfers only one electron at a time to the MoFe protein in a process that requires the hydrolysis of two ATP.

更新日期：2023-03-01

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