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首页> 外文期刊>Journal of bacteriology >WrbA from Escherichia coli and Archaeoglobus fulgidus Is an NAD(P)H:Quinone Oxidoreductase
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WrbA from Escherichia coli and Archaeoglobus fulgidus Is an NAD(P)H:Quinone Oxidoreductase

机译：大肠杆菌和古生菌的WrbA是NAD（P）H：醌醌氧化还原酶

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WrbA (tryptophan [W] repressor-binding protein) was discovered in Escherichia coli, where it was proposed to play a role in regulation of the tryptophan operon; however, this has been put in question, leaving the function unknown. Here we report a phylogenetic analysis of 30 sequences which indicated that WrbA is the prototype of a distinct family of flavoproteins which exists in a diversity of cell types across all three domains of life and includes documented NAD(P)H:quinone oxidoreductases (NQOs) from the Fungi and Viridiplantae kingdoms. Biochemical characterization of the prototypic WrbA protein from E. coli and WrbA from Archaeoglobus fulgidus, a hyperthermophilic species from the Archaea domain, shows that these enzymes have NQO activity, suggesting that this activity is a defining characteristic of the WrbA family that we designate a new type of NQO (type IV). For E. coli WrbA, the KmNADH was 14 ± 0.43 μM and the Kmbenzoquinone was 5.8 ± 0.12 μM. For A. fulgidus WrbA, the KmNADH was 19 ± 1.7 μM and the Kmbenzoquinone was 37 ± 3.6 μM. Both enzymes were found to be homodimeric by gel filtration chromatography and homotetrameric by dynamic light scattering and to contain one flavin mononucleotide molecule per monomer. The NQO activity of each enzyme is retained over a broad pH range, and apparent initial velocities indicate that maximal activities are comparable to the optimum growth temperature for the respective organisms. The results are discussed and implicate WrbA in the two-electron reduction of quinones, protecting against oxidative stress.
机译：在大肠杆菌中发现了WrbA（色氨酸[W]阻遏物结合蛋白），该蛋白被认为在色氨酸操纵子的调控中起作用。但是，这一直是个问题，功能未知。在这里，我们报告了30个序列的系统发育分析，表明WrbA是黄素蛋白不同家族的原型，其存在于生命的所有三个域中的多种细胞类型中，并且包括已记录的NAD（P）H：醌氧化还原酶（NQOs）来自 Fungi 和 Viridiplantae 王国。来自 E的原型WrbA蛋白的生化特征。 Archaeoglobus fulgidus 的大肠埃希氏杆菌和WrbA是来自 Archaea 域的超嗜热菌，表明这些酶具有NQO活性，表明这种活性是WrbA系列，我们指定了一种新型的NQO（IV型）。对于 E。大肠杆菌WrbA， K m NADH 为14±0.43μM， K m 苯醌为5.8±0.12μM。对于 A。 fulgidus WrbA， K m NADH 为19±1.7μM， K m 苯醌为37±3.6μM。通过凝胶过滤色谱法发现两种酶是同二聚体，通过动态光散射发现这两种酶是同四聚体，并且每个单体包含一个黄素单核苷酸分子。每种酶的NQO活性均在很宽的pH范围内保持，并且明显的初始速度表明最大活性与相应生物体的最佳生长温度相当。讨论了结果，并暗示了WrbA参与醌的双电子还原，可防止氧化应激。

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