In vivo requirement for glutaredoxins and thioredoxins in the reduction of the ribonucleotide reductases of Escherichia coli
In vivo requirement for glutaredoxins and thioredoxins in the reduction of the ribonucleotide reductases of Escherichia coli
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DOI：
10.1089/ars.2006.8.735
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发表时间：
2006-05-01
影响因子：
6.6
通讯作者：
Beckwith, Jon
中科院分区：
文献类型：
--
作者：
Gon, Stephanie;Faulkner, Melinda J.;Beckwith, Jon
大肠杆菌表达三种类型的核糖核苷酸还原酶（RNR），其利用半胱氨酸的氧化还原化学来催化核糖核苷酸的还原。在还原时，半胱氨酸形成二硫键并且必须被还原。作者提出了体内研究，阐明了这些酶再生的机制。Ia类酶NrdAB可以被硫氧还蛋白1和2或谷氧还蛋白1还原。Ib类酶NrdEF在体内被专用的谷氧还蛋白样蛋白NrdH还原。尽管它与谷氧还蛋白相似，但这种蛋白本身在体内被硫氧还蛋白还原酶还原。然而，在缺乏硫氧还蛋白还原酶和NrdH的情况下，谷氧还蛋白1可以部分取代NrdH。尽管它们的结构相似，但NrdEF和NrdAB RNR在低氧条件下的功能能力不同。只有微量的氧气存在，NrdAB可以允许在没有厌氧酶NrdDG的情况下进行一些生长。NrdEF不能。此外，在厌氧条件下，E.大肠杆菌的生长依赖于III类RNR、NrdDG，并且依赖于具有两种还原系统（硫氧还蛋白还原酶或谷胱甘肽还原酶）中的至少一种。这些研究结果表明，这些酶的作用，无论是NrdDG再活化或其他一些重要的厌氧过程。
Escherichia coli expresses three types of ribonucleotide reductases (RNRs) that utilize the redox chemistry of cysteine to catalyze the reduction of ribonucleotides. Upon reduction, the cysteines form a disulfide bond and must be reduced. The authors present in vivo studies that shed light on the mechanism by which these enzymes are regenerated. The class la enzyme, NrdAB, can be reduced by either the thioredoxins 1 and 2 or by glutaredoxin 1. The class Ib enzyme, NrdEF, is reduced in vivo by a dedicated glutaredoxin-like protein, NrdH. Despite its similarities to glutaredoxins, this protein is itself reduced by thioredoxin reductase in vivo. However, in the absence of thioredoxin reductase and NrdH, glutaredoxin 1 can partially replace NrdH. Despite their similar structures, the NrdEF and NrdAB RNRs differ in their abilities to function under low oxygen conditions. With only traces of oxygen present, NrdAB can allow some growth in the absence of the anaerobic enzyme NrdDG. NrdEF cannot. Furthermore, in anaerobiosis, E. coli is dependent for growth on class III RNR, NrdDG, and on having at least one of the two reductive systems, thioredoxin reductase or glutathione reductase. These findings indicate a role for these enzymes either for NrdDG reactivation or some other essential anaerobic process.