Oxidative titration of the nitrogenase VFe protein from Azotobacter vinelandii: an example of redox-gated electron flow.
Oxidative titration of the nitrogenase VFe protein from Azotobacter vinelandii: an example of redox-gated electron flow.
复制标题
葡萄固氮菌固氮酶 VFe 蛋白的氧化滴定：氧化还原门控电子流的一个例子。
DOI：
10.1021/bi951430i
复制
发表时间：
1996
期刊：
影响因子：
--
通讯作者：
Hales,BJ
中科院分区：
文献类型：
--
作者：
Tittsworth,RC;Hales,BJ
棕色固氮菌（Azotobacter vinelandii）固氮酶VFe蛋白（Av 1 '）以两种形式存在，即Av 1' A和Av 1 'B，前者具有α2β 2三聚体结构，后者具有α2β 2四聚体结构[Blanchard，C. Z.，& Hales，B. J.（1996）Biochemistry 35，472 - 478]。两者在隔离状态下都形成了5/2的EPR信号，可以被分配给1-当量氧化的P簇（P+）。这些信号通过用组分2蛋白（Av 2 '）进行酶促还原而消除。酶促还原的Av 1 'B的逐步氧化滴定导致S = 5/2 P+信号的恢复和S = 3/2钒辅因子信号的同时降低。进一步的氧化导致出现一个整数自旋信号，该信号被分配给2当量氧化的P簇（P2+）。与先前在Mo固氮酶组分1（Av 1）中观察到的类似信号不同，Av 1 'B中的整数自旋P2+信号源自基态双峰。类似的氧化滴定酶促还原Av 1 'A显示氧化还原行为显着不同的Av 1' B，通过EPR光谱监测。我们观察到的氧化还原诱导的分子内电子转移之间的还原P集群和氧化的FeV辅因子集群在滴定的光谱证据。
The nitrogenase VFe protein ofAzotobacter vinelandii(Av1‘) has been shown to exist in two forms called Av1‘A, which has a primary αβ2trimeric structure, and Av1‘B, which has an α2β2tetrameric structure [Blanchard, C. Z., & Hales, B. J. (1996)Biochemistry 35, 472−478]. Both forms exhibitS= 5/2 EPR signals in the as-isolated state that may be assigned to 1-equiv-oxidized P clusters (P+). These signals are abolished by enzymatic reduction with the component 2 protein (Av2‘). Stepwise oxidative titrations of enzymatically reduced Av1‘Bresult in the restoration of theS= 5/2 P+signals and the concurrent decrease of theS= 3/2 vanadium cofactor signal. Further oxidation results in the appearance of an integer spin signal assigned to the 2-equiv−oxidized P cluster (P2+). Unlike the analogous signal previously observed in Mo nitrogenase component 1 (Av1), which arises from an excited state, the integer spin P2+signal in Av1‘Boriginates from a ground-state doublet. Similar oxidative titrations of enzymatically reduced Av1‘Ashow redox behavior dramatically different from that of Av1‘B, as monitored by EPR spectroscopy. We observe spectral evidence for a redox-induced intramolecular electron transfer between the reduced P cluster and the oxidized FeV cofactor cluster during the titrations.