Su Tao, Si Meiru, Zhao Yunfeng, Liu Yan, Yao Shumin, Che Chengchuan, Chen Can
College of Life Sciences, Qufu Normal University, Qufu, Shandong, China.
School of Geography And Tourism, Qufu Normal University, Rizhao, Shandong, China.
PLoS One. 2018 Feb 13;13(2):e0192674. doi: 10.1371/journal.pone.0192674. eCollection 2018.
Peroxiredoxin Q (PrxQ) that belonged to the cysteine-based peroxidases has long been identified in numerous bacteria, but the information on the physiological and biochemical functions of PrxQ remain largely lacking in Corynebacterium glutamicum. To better systematically understand PrxQ, we reported that PrxQ from model and important industrial organism C. glutamicum, encoded by the gene ncgl2403 annotated as a putative PrxQ, played important roles in adverse stress resistance. The lack of C. glutamicum prxQ gene resulted in enhanced cell sensitivity, increased ROS accumulation, and elevated protein carbonylation levels under adverse stress conditions. Accordingly, PrxQ-mediated resistance to adverse stresses mainly relied on the degradation of ROS. The physiological roles of PrxQ in resistance to adverse stresses were corroborated by its induced expression under adverse stresses, regulated directly by the stress-responsive ECF-sigma factor SigH. Through catalytical kinetic activity, heterodimer formation, and bacterial two-hybrid analysis, we proved that C. glutamicum PrxQ catalytically eliminated peroxides by exclusively receiving electrons from thioredoxin (Trx)/thioredoxin reductase (TrxR) system and had a broad range of oxidizing substrates, but a better efficiency for peroxynitrite and cumene hydroperoxide (CHP). Site-directed mutagenesis confirmed that the conserved Cys49 and Cys54 are the peroxide oxidation site and the resolving Cys residue, respectively. It was also discovered that C. glutamicum PrxQ mainly existed in monomer whether under its native state or functional state. Based on these results, a catalytic model of PrxQ is being proposed. Moreover, our result that C. glutamicum PrxQ can prevent the damaging effects of adverse stresses by acting as thioredoxin-dependent monomeric peroxidase could be further applied to improve the survival ability and robustness of the important bacterium during fermentation process.
过氧化物酶Q（PrxQ）属于基于半胱氨酸的过氧化物酶，长期以来在众多细菌中都有发现，但关于谷氨酸棒杆菌中PrxQ的生理生化功能的信息仍然十分匮乏。为了更好地系统了解PrxQ，我们报道了来自模式及重要工业微生物谷氨酸棒杆菌的PrxQ（由注释为假定PrxQ的ncgl2403基因编码）在抗逆胁迫中发挥重要作用。谷氨酸棒杆菌prxQ基因的缺失导致细胞敏感性增强、活性氧（ROS）积累增加以及在逆境胁迫条件下蛋白质羰基化水平升高。因此，PrxQ介导的抗逆胁迫主要依赖于ROS的降解。PrxQ在抗逆胁迫中的生理作用通过其在逆境胁迫下的诱导表达得到证实，它直接受应激反应性的ECF-σ因子SigH调控。通过催化动力学活性、异源二聚体形成及细菌双杂交分析，我们证明谷氨酸棒杆菌PrxQ通过专门从硫氧还蛋白（Trx）/硫氧还蛋白还原酶（TrxR）系统接收电子来催化消除过氧化物，并且具有广泛的氧化底物，但对过氧亚硝酸根和氢过氧化异丙苯（CHP）具有更高的催化效率。定点诱变证实保守的半胱氨酸49和半胱氨酸54分别是过氧化物氧化位点和解决性半胱氨酸残基。还发现谷氨酸棒杆菌PrxQ无论在天然状态还是功能状态下主要都以单体形式存在。基于这些结果，我们提出了PrxQ的催化模型。此外，我们关于谷氨酸棒杆菌PrxQ作为硫氧还蛋白依赖性单体过氧化物酶可防止逆境胁迫造成破坏作用的结果，可进一步应用于提高这种重要细菌在发酵过程中的生存能力和稳健性。
