Ingelman M, Bianchi V, Eklund H
Department of Molecular Biology, Swedish University of Agricultural Sciences, Uppsala Biomedical Center.
J Mol Biol. 1997 Apr 25;268(1):147-57. doi: 10.1006/jmbi.1997.0957.
Flavodoxin reductase from Escherichia coli is an FAD-containing oxidoreductase that transports electrons between flavodoxin or ferredoxin and NADPH. Together with flavodoxin, the enzyme is involved in the reductive activation of three E. coli enzymes: cobalamin-dependent methionine synthase, pyruvate formate lyase and anaerobic ribonucleotide reductase. An additional function for the oxidoreductase appears to be to protect the bacteria against oxygen radicals. The three-dimensional structure of flavodoxin reductase has been solved by multiple isomorphous replacement, and has been refined at 1.7 A to an R-value of 18.4% and Rfree 24.8%. The monomeric molecule contains one beta-sandwich FAD domain and an alpha/beta NADP domain. The overall structure is similar to other reductases of the NADP-ferredoxin reductase family in spite of the low sequence similarities within the family. Flavodoxin reductase lacks the loop which is involved in the binding of the adenosine moiety of FAD in other FAD binding enzymes of the superfamily but is missing in the FMN binding phthalate dioxygenase reductase. Instead of this loop, the adenine interacts with an extra tryptophan at the C terminus. The FAD in flavodoxin reductase has an unusual bent conformation with a hydrogen bond between the adenine and the isoalloxazine. This is probably the cause of the unusual spectrum of the enzyme. There is a pronounced cleft close to the isoalloxazine that appears to be well suited for binding of flavodoxin/ferredoxin. Two extra short strands of the NADP-binding domain probably act as an anchor point for the binding of flavodoxin.
来自大肠杆菌的黄素氧还蛋白还原酶是一种含黄素腺嘌呤二核苷酸（FAD）的氧化还原酶，它在黄素氧还蛋白或铁氧还蛋白与烟酰胺腺嘌呤二核苷酸磷酸（NADPH）之间传递电子。该酶与黄素氧还蛋白一起参与了大肠杆菌三种酶的还原激活：钴胺素依赖性甲硫氨酸合成酶、丙酮酸甲酸裂解酶和厌氧核糖核苷酸还原酶。这种氧化还原酶的另一个功能似乎是保护细菌免受氧自由基的侵害。黄素氧还蛋白还原酶的三维结构已通过多同晶置换法解析，并在1.7埃分辨率下进行了精修，R值为18.4%，自由R值为24.8%。单体分子包含一个β-折叠FAD结构域和一个α/β NADP结构域。尽管该家族内序列相似性较低，但整体结构与NADP-铁氧还蛋白还原酶家族的其他还原酶相似。黄素氧还蛋白还原酶缺乏在超家族其他FAD结合酶中参与FAD腺苷部分结合的环，但在FMN结合的邻苯二甲酸二加氧酶还原酶中不存在。取而代之的是，腺嘌呤与C末端的一个额外色氨酸相互作用。黄素氧还蛋白还原酶中的FAD具有不寻常的弯曲构象，腺嘌呤与异咯嗪之间存在氢键。这可能是该酶具有不寻常光谱的原因。在异咯嗪附近有一个明显的裂缝，似乎非常适合黄素氧还蛋白/铁氧还蛋白的结合。NADP结合结构域的两条额外短链可能作为黄素氧还蛋白结合的锚定点。
