Gamma-glutamylcysteine protects ergothioneine-deficient Mycobacterium tuberculosis mutants against oxidative and nitrosative stress

• Published in: Biochemical and biophysical research communications 2018-01, Vol.495 (1), p.174-178
• Main Authors: Sao Emani, C., Williams, M.J., Van Helden, P.D., Taylor, M.J.C., Wiid, I.J., Baker, B.
• Format: Article
• Language: English
• Subjects: 60 APPLIED LIFE SCIENCES; BIOSYNTHESIS; Biosynthetic Pathways; Cysteine - genetics; Cysteine - metabolism; DETOXIFICATION; Dipeptides - genetics; Dipeptides - metabolism; Ergothioneine (ERG); Ergothioneine - genetics; Ergothioneine - metabolism; Gamma-glutamylcysteine (GGC); Gene Deletion; Glutathione (GSH); Glycopeptides - genetics; Glycopeptides - metabolism; Humans; Inositol - genetics; Inositol - metabolism; MYCOBACTERIUM TUBERCULOSIS; Mycobacterium tuberculosis - genetics; Mycobacterium tuberculosis - metabolism; Mycothiol (MSH); Nitrosative Stress; Oxidative Stress; Reactive nitrogen species (RNS); Reactive oxygen species (ROS); THIOLS; TUBERCULOSIS; Tuberculosis - microbiology
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/j.bbrc.2017.10.163

Mycobacterium tuberculosis (M.tb.), the causative agent of tuberculosis (TB), cannot synthesize GSH, but synthesizes two major low molecular weight thiols namely mycothiol (MSH) and ergothioneine (ERG). Gamma-glutamylcysteine (GGC), an intermediate in GSH synthesis, has been implicated in the protection of lactic acid bacteria from oxidative stress in the absence of GSH. In mycobacteria, GGC is an intermediate in ERG biosynthesis, and its formation is catalysed by EgtA (GshA). GGC is subsequently used by EgtB in the formation of hercynine-sulphoxide-GGC. In this study, M.tb. mutants harbouring unmarked, in-frame deletions in each of the fives genes involved in ERG biosynthesis (egtA, egtB, egtC, egtD and egtE) or a marked deletion of the mshA gene (required for MSH biosynthesis) were generated. Liquid chromatography tandem mass spectrometry analyses (LC-MS) revealed that the production of GGC was elevated in the MSH-deficient and the ERG-deficient mutants. The ERG-deficient ΔegtB mutant which accumulated GGC was more resistant to oxidative and nitrosative stress than the ERG-deficient, GGC-deficient ΔegtA mutant. This implicates GGC in the detoxification of reactive oxygen and nitrogen species in M.tb. [Display omitted] •EgtA is essential for gamma-glutamylcysteine biosynthesis.•EgtE is not essential for ergothioneine biosynthesis.•EgtC is partially compensated for in ergothioneine biosynthesis.•The production of gamma-glutamylcysteine is elevated in thiol-deficient M. tuberculosis mutants.•Gamma-glutamylcysteine protects thiol-deficient M. tuberculosis mutants.