Correlations of structure and electronic properties from EPR spectroscopy of hydroxylamine oxidoreductase
Correlations of structure and electronic properties from EPR spectroscopy of hydroxylamine oxidoreductase
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DOI：
10.1021/ja002982d
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发表时间：
2001-04-04
影响因子：
15
通讯作者：
Hooper, AB
中科院分区：
文献类型：
--
作者：
Hendrich, MP;Petasis, D;Hooper, AB
来自自养硝化细菌亚硝化单胞菌的羟胺氧化还原酶（HAO）催化NH 2 OH氧化成HNO 2。该酶每个亚基含有8个血红素，参与催化功能和电子传递。该酶的结构显示了八个血红素的独特空间排列，其中的子集现在在其他四种蛋白质中观察到。空间排列显示三种类型的双血红素配对基序。八个血红素中至少有四个以两个可区分的对电子耦合，并且这些对中的一个在酶的活性位点处。在这里，EPR信号的定量模拟的使用允许交换耦合的确定，和信号和还原电位的晶体结构的血红素的分配。在晶体结构中没有任何明显的血红素-血红素键合途径，表明所观察到的交换相互作用来自卟啉轨道的直接电子重叠。这为血红素对在电子转移过程中作为生物双电子氧化还原中心提供了证据。
Hydroxylamine oxidoreductase (HAO) from the autotrophic nitrifying bacterium Nitrosomonas europaea catalyzes the oxidation of NH2OH to HNO2. The enzyme contains eight hemes per subunit which participate in catalytic function and electron transport. The structure of the enzyme shows a unique spatial arrangement of the eight hemes, subsets of which are now observed in four other proteins. The spatial arrangement displays three types of diheme pairing motifs. At least four of the eight hemes are electronically coupled in two distinguishable pairs and one of these pairs is at the active site of the enzyme. Here, the use of quantitative simulation of the EPR signals allows determination of exchange couplings, and assignments of signals and reduction potentials to hemes of the crystal structure. The absence of any obvious heme-to-heme bonding pathway in the crystal structure suggests that the observed exchange interactions are derived from direct electronic overlap of porphyrin orbitals. This provides evidence for heme pairs which function as biological two-electron redox centers in electron-transfer processes.