Structure and spectroscopy of the periplasmic cytochrome c nitrite reductase from Escherichia coli
Structure and spectroscopy of the periplasmic cytochrome c nitrite reductase from Escherichia coli
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DOI：
10.1021/bi015765d
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发表时间：
2002-03-05
期刊：
影响因子：
2.9
通讯作者：
Richardson, DJ
中科院分区：
文献类型：
--
作者：
Bamford, VA;Angove, HC;Richardson, DJ
报道了大肠杆菌胞质五血红素细胞色素c亚硝酸还原酶（NrfA）的晶体结构和光谱性质。该结构是第一个利用可溶性五血红素细胞色素NrfB作为氧化还原伴侣的NrfA亚组成员。比较Wolinella succinogenes NrfA和Sulfoacellum deleyianum NrfA的结构，它接受来自膜锚定的四血红素细胞色素（NrfH）的电子，揭示了血红素2周围的蛋白质表面的显着差异，这可能是对接网站的氧化还原伙伴。结构显示NrfA血红素中的四个（血红素2-5）具有双组氨酸轴向血红素-Fe连接。催化血红素-Fe（血红素1）具有赖氨酸远端配体和氧原子近端配体。通过磁性圆二色性（MCD）分析溶液中的NrfA，表明氧配体来自于水。从电化学平衡的NrfA样品中收集电子顺磁共振（EPR）光谱。在g类似于10.8和3.5的宽垂直模式信号，弱自旋耦合S = 5/2，S = 1/2顺磁体的特征，用E-m = -107 mV滴定。这些可能的起源是活性位点Lys-OH 2配位的血红素（血红素1）和附近的双-His配位的血红素（血红素3）。当E-m = -37 mV时，在g（z）= 2.91，g（y）= 2.3，g（x）= 1.5处出现菱形血红素Fe（III）EPR信号，可能是由咪唑环的面间角为21.2 °的双组氨酸配位血红素（血红素2）引起的。最后两个双组氨酸配位的血红素（血红素4和5）的咪唑平面角分别为64.4度和71.8度。这两种血红素中的一种或两种可以在g（z）= 3.17处产生“大g max”EPR信号，其在-250 mV和-400 mV之间的电位下滴定。根据对大肠杆菌NrfA的基于结构的光谱电位分析，考虑了以前对一些细菌物种NrfA的光谱研究。coli NrfA.
The crystal structure and spectroscopic properties of the periplasmic penta-heme cytochrome c nitrite reductase (NrfA) of Escherichia coli are presented. The structure is the first for a member of the NrfA subgroup that utilize a soluble penta-heme cytochrome, NrfB, as a redox partner. Comparison to the structures of Wolinella succinogenes NrfA and Sulfospirillum deleyianum NrfA, which accept electrons from a membrane-anchored tetra-heme cytochrome (NrfH), reveals notable differences in the protein surface around heme 2, which may be the docking site for the redox partner. The structure shows that four of the NrfA hemes (hemes 2-5) have bis-histidine axial heme-Fe ligation. The catalytic heme-Fe (heme 1) has a lysine distal ligand and an oxygen atom proximal ligand. Analysis of NrfA in solution by magnetic circular dichroism (MCD) suggested that the oxygen ligand arose from water. Electron paramagnetic resonance (EPR) spectra were collected from electrochemically poised NrfA samples. Broad perpendicular mode signals at g similar to 10.8 and 3.5, characteristic of weakly spin-coupled S = 5/2, S = 1/2 paramagnets, titrated with E-m = -107 mV. A possible origin for these are the active site Lys-OH2 coordinated heme (heme 1) and a nearby bis-His coordinated heme (heme 3). A rhombic heme Fe(III) EPR signal at g(z) = 2.91, g(y) = 2.3, g(x) = 1.5 titrated with E-m = -37 mV and is likely to arise from bis-His coordinated heme (heme 2) in which the interplanar angle of the imidazole rings is 21.2degrees. The final two bis-His coordinated hemes (hemes 4 and 5) have imidazole interplanar angles of 64.4degrees and 71.8degrees. Either, or both, of these hemes could give rise to a "Large g max" EPR signal at g(z) = 3.17 that titrated at potentials between -250 and -400 mV. Previous spectroscopic studies on NrfA from a number of bacterial species are considered in the light of the structure-based spectro-potentiometric analysis presented for the E. coli NrfA.