Browsing by Author "Williams, M. J."

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    The functional interplay of low molecular weight thiols in Mycobacterium tuberculosis
    (BioMed Central, 2018-07-12) Sao Emani, C.; Williams, M. J.; Wiid, I. J.; Baker, B.
    Background: Three low molecular weight thiols are synthesized by Mycobacterium tuberculosis (M.tb), namely ergothioneine (ERG), mycothiol (MSH) and gamma-glutamylcysteine (GGC). They are able to counteract reactive oxygen species (ROS) and/or reactive nitrogen species (RNS). In addition, the production of ERG is elevated in the MSH-deficient M.tb mutant, while the production of MSH is elevated in the ERG-deficient mutants. Furthermore, the production of GGC is elevated in the MSH-deficient mutant and the ERG-deficient mutants. The propensity of one thiol to be elevated in the absence of the other prompted further investigations into their interplay in M.tb. Methods: To achieve that, we generated two M.tb mutants that are unable to produce ERG nor MSH but are able to produce a moderate (ΔegtD-mshA) or significantly high (ΔegtB-mshA) amount of GGC relative to the wild-type strain. In addition, we generated an M.tb mutant that is unable to produce GGC nor MSH but is able to produce a significantly low level of ERG (ΔegtA-mshA) relative to the wild-type strain. The susceptibilities of these mutants to various in vitro and ex vivo stress conditions were investigated and compared. Results: The ΔegtA-mshA mutant was the most susceptible to cellular stress relative to its parent single mutant strains (ΔegtA and ∆mshA) and the other double mutants. In addition, it displayed a growth-defect in vitro, in mouse and human macrophages suggesting; that the complete inhibition of ERG, MSH and GGC biosynthesis is deleterious for the growth of M.tb. Conclusions: This study indicates that ERG, MSH and GGC are able to compensate for each other to maximize the protection and ensure the fitness of M.tb. This study therefore suggests that the most effective strategy to target thiol biosynthesis for anti-tuberculosis drug development would be the simultaneous inhibition of the biosynthesis of ERG, MSH and GGC.
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    Generation and characterization of thiol-deficient Mycobacterium tuberculosis mutants
    (Nature Research, 2018) Emani, C. Sao; Williams, M. J.; Van Helden, Paul D.; Taylor, M. J. C.; Carolis, C.; Wiid, I. J.; Baker, B.
    Mycothiol (MSH) and ergothioneine (ERG) are thiols able to compensate for each other to protect mycobacteria against oxidative stress. Gamma-glutamylcysteine (GGC), another thiol and an intermediate in ERG biosynthesis has detoxification abilities. Five enzymes are involved in ERG biosynthesis, namely EgtA, EgtB, EgtC, EgtD and EgtE. The role of these enzymes in the production of ERG had been unclear. On the other hand, the enzyme MshA is known to be essential for MSH biosynthesis. In this manuscript, we describe the raw data of the generation and characterization of Mycobacterium tuberculosis (M.tb) mutants harbouring a deletion of the gene coding for each of these enzymes, and the raw data of the phenotypic characterization of the obtained thiol-deficient M.tb mutants. High throughput screening (HTS) of off-patent drugs and natural compounds revealed few compounds that displayed a higher activity against the thiol-deficient mutants relative to the wild-type strain. The mode of action of these drugs was further investigated. Raw data displaying these results are described here.