Uncoupling nitrogenase: catalytic reduction of hydrazine to ammonia by a MoFe protein in the absence of Fe protein-ATP.
Uncoupling nitrogenase: catalytic reduction of hydrazine to ammonia by a MoFe protein in the absence of Fe protein-ATP.
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DOI：
10.1021/ja1067178
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发表时间：
2010-09-29
影响因子：
15
通讯作者：
Seefeldt, Lance C.
中科院分区：
文献类型：
--
作者：
Danyal, Karamatullah;Inglet, Boyd S.;Vincent, Kylie A.;Barney, Brett M.;Hoffman, Brian M.;Armstrong, Fraser A.;Dean, Dennis R.;Seefeldt, Lance C.
报道了在无Fe蛋白或ATP存在下，β-98 Tyr-HisMoFe蛋白催化肼（N_2H_4）还原为氨的反应。N2或其他底物（例如，肼、质子、乙炔）通常需要两种固氮酶组分蛋白质（Fe蛋白质和MoFe蛋白质）的瞬时结合。铁蛋白，与两个绑定的MgATP分子，转移一个电子的MoFe蛋白在每个协会，耦合到两个MgATP的水解。固氮酶催化的所有底物还原反应都需要Fe蛋白与MgATP水解偶联传递电子。我们报告说，当MoFe蛋白（β-98 Tyr）中的一个氨基酸被His取代时，当提供低电位还原剂聚氨基羧酸连接的EuII（Em−1.1 V vs NHE）时，所得MoFe蛋白支持含氮底物肼（N2 H4）催化还原为两个氨分子。在这些条件下，野生型和许多其他具有氨基酸取代的MoFe蛋白质不显示出显著的肼还原速率，而β-98HisMoFe蛋白质以高达170 nmol NH3/min/mg MoFe蛋白质的速率催化肼还原。当与Fe蛋白、ATP和还原剂在相当的条件下组合时，肼还原的速率是由β-98His或野生型MoFe蛋白催化的速率的94%。在不存在Fe蛋白的情况下，肼的β-98HisMoFe蛋白还原显示还原剂和底物浓度的饱和动力学。这些结果在理解固氮酶机制的影响进行了讨论。
The catalytic reduction of hydrazine (N2H4) to ammonia by a β-98Tyr→HisMoFe protein in the absence of the Fe protein or ATP is reported. The reduction of N2or other substrates (e.g., hydrazine, protons, acetylene) by nitrogenase normally requires the transient association of the two nitrogenase component proteins, the Fe protein and the MoFe protein. The Fe protein, with two bound MgATP molecules, transfers one electron to the MoFe protein during each association, coupled to the hydrolysis of two MgATP. All substrate reduction reactions catalyzed by nitrogenase require delivery of electrons by the Fe protein coupled to the hydrolysis of MgATP. We report that when a single amino acid within the MoFe protein (β-98Tyr) is substituted by His, the resulting MoFe protein supports catalytic reduction of the nitrogenous substrate hydrazine (N2H4) to two ammonia molecules when provided with a low potential reductant, polyaminocarboxylate ligated EuII(Em−1.1 V vs NHE). The wild-type and a number of other MoFe proteins with amino acid substitutions do not show significant rates of hydrazine reduction under these conditions, whereas the β-98HisMoFe protein catalyzes hydrazine reduction at rates up to 170 nmol NH3/min/mg MoFe protein. This rate of hydrazine reduction is 94% of the rate catalyzed by the β-98Hisor wild-type MoFe protein when combined with the Fe protein, ATP, and reductant under comparable conditions. The β-98HisMoFe protein reduction of hydrazine in the absence of the Fe protein showed saturation kinetics for the concentration of reductant and substrate. The implications of these results in understanding the nitrogenase mechanism are discussed.
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影响因子：
4.8
作者：
Barney, BM;Igarashi, RY;Seefeldt, LC
通讯作者：
Seefeldt, LC
影响因子：
56.9
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作者：
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影响因子：
16.6
作者：
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通讯作者：
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