Thiol Reductases in Deinococcus Bacteria and Roles in Stress Tolerance

Abstract

Deinococcus species possess remarkable tolerance to extreme environmental conditions that generate oxidative damage to macromolecules. Among enzymes fulfilling key functions in metabolism regulation and stress responses, thiol reductases (TRs) harbour catalytic cysteines modulating the redox status of Cys and Met in partner proteins. We present here a detailed description of Deinococcus TRs regarding gene occurrence, sequence features, and physiological functions that remain poorly characterised in this genus. Two NADPH-dependent thiol-based systems are present in Deinococcus. One involves thioredoxins, disulfide reductases providing electrons to protein partners involved notably in peroxide scavenging or in preserving protein redox status. The other is based on bacillithiol, a low-molecular-weight redox molecule, and bacilliredoxin, which together protect Cys residues against overoxidation. Deinococcus species possess various types of thiol peroxidases whose electron supply depends either on NADPH via thioredoxins or on NADH via lipoylated proteins. Recent data gained on deletion mutants confirmed the importance of TRs in Deinococcus tolerance to oxidative treatments, but additional investigations are needed to delineate the redox network in which they operate, and their precise physiological roles. The large palette of Deinococcus TR representatives very likely constitutes an asset for the maintenance of redox homeostasis in harsh stress conditions.

Unraveling radiation resistance strategies in two bacterial strains from the high background radiation area of Chavara-Neendakara: A comprehensive whole genome analysis

“…The exact function of this gene is still elusive in D . radiodurans [ 126 ], although irradiation is reported to have induced its expression [ 127 ].…”

DNA repair and oxidative stress defense systems in radiation-resistant Deinococcus murrayi

“…While DNA is not protected from damage, it has been shown that proteins in radiation-resistant organisms are much better protected against oxidative damage than in radiation-sensitive organisms (Daly et al 2007). Deinococcus bacteria are well equipped with enzymatic and non-enzymatic antioxidant systems (Slade and Radman 2011;Daly 2012;Lim et al 2019;de Groot et al 2022). Identified non-enzymatic antioxidant systems and compounds are a high intracellular Mn 2+ /Fe 2+ ratio (limiting Fe 2+ -catalyzed oxidative damage to proteins), small-molecule Mn 2+ -antioxidant complexes, small peptides, carotenoids, and the low-molecular-weight thiol bacillithiol (Daly et al 2004(Daly et al , 2010Tian and Hua 2010;Berlett and Levine 2014;Jeong et al 2021a).…”

“…Identified non-enzymatic antioxidant systems and compounds are a high intracellular Mn 2+ /Fe 2+ ratio (limiting Fe 2+ -catalyzed oxidative damage to proteins), small-molecule Mn 2+ -antioxidant complexes, small peptides, carotenoids, and the low-molecular-weight thiol bacillithiol (Daly et al 2004(Daly et al , 2010Tian and Hua 2010;Berlett and Levine 2014;Jeong et al 2021a). Antioxidant enzymes are also important for survival of Deinococcus when exposed to radiation (acute or chronic), desiccation, or oxidants (Lim et al 2019;de Groot et al 2022;Gaidamakova et al 2022;Han et al 2022) (and references therein). These enzymes are for example involved in ROS removal (e.g., superoxide dismutase, catalase, and peroxiredoxin), and protection and repair of oxidation-sensitive cysteine and methionine residues in proteins (thiol reductases).…”

“…Many genes and proteins, including regulators, and also non-enzymatic antioxidants such as carotenoids and Mn 2+ -containing complexes, that contribute to radiation and/or oxidative stress resistance, have been identified (Daly et al 2010;Slade and Radman 2011;Dulermo et al 2015;Lim et al 2019). The conservation of proteins involved in these stress resistance mechanisms has been investigated in a set of other Deinococcus species isolated worldwide, which not only revealed conservation but also remarkable diversity of these proteins among deinococci (Lim et al 2019;de Groot et al 2022).…”

The Transposition of Insertion Sequences in Sigma-Factor- and LysR-Deficient Mutants of Deinococcus geothermalis

“…A couple of Deinococcus strains are relatively well studied for their physiological protective mechanisms under oxidative stress. Various types of protective mechanisms have been described, including (1) pigment-dependent protection with carotenoids, (2) enzymatic defense mechanisms with catalase, peroxidase and superoxide dismutase, (3) metal-ion-dependent protection with the regulation of the iron/manganese ratio, ( 4) examples of well-known stress response regulators including the general antioxidative activator OxyR, superoxide response protein SoxRS, and the alternative sigma factor RpoS, and (5) the regulation of intracellular redox potential by thiol concentrations via cystine import and biosynthesis [2][3][4][5][6][7][8][9][10][11][12][13][14].…”