MsrR is a thiol-based oxidation-sensing regulator of the XRE family that modulates C. glutamicum oxidative stress resist
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Microbial Cell Factories Open Access
RESEARCH
MsrR is a thiol‑based oxidation‑sensing regulator of the XRE family that modulates C. glutamicum oxidative stress resistance Meiru Si1*† , Can Chen2†, Jingyi Zhong1, Xiaona Li1, Yang Liu1, Tao Su1 and Ge Yang1*
Abstract Background: Corynebacterium glutamicum thrives under oxidative stress caused by the inevitably extreme environment during fermentation as it harbors antioxidative stress genes. Antioxidant genes are controlled by pathwayspecific sensors that act in response to growth conditions. Although many families of oxidation-sensing regulators in C. glutamicum have been well described, members of the xenobiotic-response element (XRE) family, involved in oxidative stress, remain elusive. Results: In this study, we report a novel redox-sensitive member of the XER family, MsrR (multiple stress resistance regulator). MsrR is encoded as part of the msrR-3-mst (3-mercaptopyruvate sulfurtransferase) operon; msrR-3-mst is divergent from multidrug efflux protein MFS. MsrR was demonstrated to bind to the intergenic region between msrR-3-mst and mfs. This binding was prevented by an MsrR oxidation-mediated increase in MsrR dimerization. MsrR was shown to use Cys62 oxidation to sense oxidative stress, resulting in its dissociation from the promoter. Elevated expression of msrR-3-mst and mfs was observed under stress. Furthermore, a ΔmsrR mutant strain displayed significantly enhanced growth, while the growth of strains lacking either 3-mst or mfs was significantly inhibited under stress. Conclusion: This report is the first to demonstrate the critical role of MsrR-3-MST-MFS in bacterial stress resistance. Keywords: Oxidative stress, MsrR, Transcription regulation, Corynebacterium glutamicum Background Reactive oxygen species (ROS), including hydrogen peroxide (H2O2), superoxide anion (O2·−), hydroxyl radical (·OH), hydroperoxy radical (HO2·), singlet oxygen (1O2), and organic hydroperoxides (OHPs), are inevitable byproducts of aerobic respiration that are also generated under environmental stress by perturbation of the electron transfer chain [1]. ROS can react with the membrane, free fatty acids, and other macromolecules via free radical chain reactions, resulting in the production *Correspondence: [email protected]; [email protected] † Meiru Si and Can Chen contributed equally to this work 1 College of Life Sciences, Qufu Normal University, Qufu 273165, Shandong, China Full list of author information is available at the end of the article
of a wide spectrum of detrimental carbonyl-containing compounds [2, 3]. The excessive production of ROS is harmful to living systems as it induces oxidative stress and causes subsequent cellular damage to molecules such as DNA, proteins, and lipids [4]. To ensure survival in a hostile environment, versatile resistance defense mechanisms, such as eliminating ROS, deterring the transformation of ROS into more toxic compounds and repairing damaged biomacromolecules, have been developed [5– 7]. Low-molecular-weight (LMW) thiols and mu
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