A novel mycothiol-dependent thiol–disulfide reductase in Corynebacterium glutamicum involving oxidative stress resistance

Abstract

Abstractncgl2478 gene from Corynebacterium glutamicum encodes a thiol–disulfide oxidoreductase enzyme annotated as dithiol–disulfide isomerase DsbA. It preserves a Cys–Pro–Phe–Cys active-site motif, which is presumed to be an exclusive characteristic of the novel DsbA–mycoredoxin 1 (Mrx1) cluster. However, the real mode of action, the nature of the electron donor pathway and biological functions of NCgl2478 in C. glutamicum have remained enigmatic so far. Herein, we report that NCgl2478 plays an important role in stress resistance. Deletion of the ncgl2478 gene increases the size of growth inhibition zones. The ncgl2478 expression is induced in the stress-responsive extra-cytoplasmic function-sigma (ECF-σ) factor SigH-dependent manner by stress. It receives electrons preferentially from the mycothiol (MSH)/mycothione reductase (Mtr)/NADPH pathway. Further, NCgl2478 reduces S-mycothiolated mixed disulfides and intramolecular disulfides via a monothiol–disulfide and a dithiol–disulfide exchange mechanism, respectively. NCgl2478 lacks oxidase activity; kinetic properties of its demycothiolation are different from those of Mrx1. Site-directed mutagenesis confirms Cys24 is the resolving Cys residue, while Cys21 is the nucleophilic cysteine that is oxidized to a sulfenic acid and then forms an intramolecular disulfide bond with Cys24 or a mixed disulfide with MSH under oxidative stress. In conclusion, our study presents the first evidence that NCgl2478 protects against various stresses by acting as an MSH-dependent thiol–disulfide reductase, belonging to a novel DsbA–Mrx1 cluster.

Combined sensor-based monitoring of mycothiol redox potential and DNA-damage response in Corynebacterium glutamicum

“…Excessive amounts of ROS can cause irreversible damages to essential cell components such as proteins, lipids or nucleic acids (Antelmann and Helmann, 2011; Imlay, 2013; Ezraty et al ., 2017). To counteract oxidative stress, C. glutamicum is equipped with effective enzymatic and non-enzymatic ROS detoxification systems (Chi et al ., 2014; Su et al ., 2018; Liu et al ., 2021). The non-enzymatic antioxidant mycothiol (MSH), for instance, has been shown to be essential to maintain a reducing environment in the cytoplasm of C. glutamicum (Van Loi et al ., 2015; Tung et al ., 2019).…”

Investigating Mtr and MshC as potential targets in the fight against Mycobacterium abscessus infections

“…reactive oxygen species (ROS) or reactive nitrogen species (RNS)), can be formed as byproducts, generating an imbalance in reductive and oxidative species termed redox stress (87,90,91). Redox stress is not only generated from intrinsic biological reactions, but can also originate from extrinsic factors, including metals, xenobiotics, antibiotics, alkylating agents, acidic pH, nutrient starvation and hypoxia, and is capable of causing damage to the DNA, RNA, lipids and proteins leading to cell death (87,89,92,93).…”