Si Mei-Ru, Zhang Lei, Yang Zhi-Fang, Xu Yi-Xiang, Liu Ying-Bao, Jiang Cheng-Ying, Wang Yao, Shen Xi-Hui, Liu Shuang-Jiang
State Key Laboratory of Crop Stress Biology for Arid Areas and College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, People's Republic of China.
Appl Environ Microbiol. 2014 Mar;80(5):1750-62. doi: 10.1128/AEM.03654-13. Epub 2013 Dec 27.
NrdH redoxins are small protein disulfide oxidoreductases behaving like thioredoxins but sharing a high amino acid sequence similarity to glutaredoxins. Although NrdH redoxins are supposed to be another candidate in the antioxidant system, their physiological roles in oxidative stress remain unclear. In this study, we confirmed that the Corynebacterium glutamicum NrdH redoxin catalytically reduces the disulfides in the class Ib ribonucleotide reductases (RNR), insulin and 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB), by exclusively receiving electrons from thioredoxin reductase. Overexpression of NrdH increased the resistance of C. glutamicum to multiple oxidative stresses by reducing ROS accumulation. Accordingly, elevated expression of the nrdH gene was observed when the C. glutamicum wild-type strain was exposed to oxidative stress conditions. It was discovered that the NrdH-mediated resistance to oxidative stresses was largely dependent on the presence of the thiol peroxidase Prx, as the increased resistance to oxidative stresses mediated by overexpression of NrdH was largely abrogated in the prx mutant. Furthermore, we showed that NrdH facilitated the hydroperoxide reduction activity of Prx by directly targeting and serving as its electron donor. Thus, we present evidence that the NrdH redoxin can protect against the damaging effects of reactive oxygen species (ROS) induced by various exogenous oxidative stresses by acting as a peroxidase cofactor.
NrdH氧化还原蛋白是一类小的蛋白质二硫键氧化还原酶，其行为类似于硫氧还蛋白，但与谷氧还蛋白具有高度的氨基酸序列相似性。尽管NrdH氧化还原蛋白被认为是抗氧化系统中的另一个候选者，但其在氧化应激中的生理作用仍不清楚。在本研究中，我们证实谷氨酸棒杆菌NrdH氧化还原蛋白通过专门从硫氧还蛋白还原酶接收电子，催化还原I b类核糖核苷酸还原酶（RNR）、胰岛素和5,5'-二硫代双（2-硝基苯甲酸）（DTNB）中的二硫键。NrdH的过表达通过减少活性氧积累，增强了谷氨酸棒杆菌对多种氧化应激的抗性。因此，当谷氨酸棒杆菌野生型菌株暴露于氧化应激条件下时，观察到nrdH基因的表达升高。研究发现，NrdH介导的对氧化应激的抗性很大程度上依赖于硫醇过氧化物酶Prx的存在，因为在prx突变体中，NrdH过表达介导的对氧化应激的抗性增强在很大程度上被消除。此外，我们表明NrdH通过直接靶向Prx并作为其电子供体，促进了Prx的氢过氧化物还原活性。因此，我们提供证据表明，NrdH氧化还原蛋白可以作为过氧化物酶辅因子，保护细胞免受各种外源性氧化应激诱导的活性氧（ROS）的损伤作用。
