Mycothiol/mycoredoxin 1-dependent reduction of the peroxiredoxin AhpE from Mycobacterium tuberculosis.

Abstract

Mycobacterium tuberculosis (M. tuberculosis), the pathogen responsible for tuberculosis, detoxifies cytotoxic peroxides produced by activated macrophages. M. tuberculosis expresses alkyl hydroxyperoxide reductase E (AhpE), among other peroxiredoxins. So far the system that reduces AhpE was not known. We identified M. tuberculosis mycoredoxin-1 (MtMrx1) acting in combination with mycothiol and mycothiol disulfide reductase (MR), as a biologically relevant reducing system for MtAhpE. MtMrx1, a glutaredoxin-like, mycothiol-dependent oxidoreductase, directly reduces the oxidized form of MtAhpE, through a protein mixed disulfide with the N-terminal cysteine of MtMrx1 and the sulfenic acid derivative of the peroxidatic cysteine of MtAhpE. This disulfide is then reduced by the C-terminal cysteine in MtMrx1. Accordingly, MtAhpE catalyzes the oxidation of wt MtMrx1 by hydrogen peroxide but not of MtMrx1 lacking the C-terminal cysteine, confirming a dithiolic mechanism. Alternatively, oxidized MtAhpE forms a mixed disulfide with mycothiol, which in turn is reduced by MtMrx1 using a monothiolic mechanism. We demonstrated the H2O2-dependent NADPH oxidation catalyzed by MtAhpE in the presence of MR, Mrx1, and mycothiol. Disulfide formation involving mycothiol probably competes with the direct reduction by MtMrx1 in aqueous intracellular media, where mycothiol is present at millimolar concentrations. However, MtAhpE was found to be associated with the membrane fraction, and since mycothiol is hydrophilic, direct reduction by MtMrx1 might be favored. The results reported herein allow the rationalization of peroxide detoxification actions inferred for mycothiol, and more recently, for Mrx1 in cellular systems. We report the first molecular link between a thiol-dependent peroxidase and the mycothiol/Mrx1 pathway in Mycobacteria.

• Authors: Martín Hugo, Koen Van Laer, Aníbal M Reyes, Didier Vertommen, Joris Messens, Rafael Radi, Madia Trujillo
• Journal: The Journal of biological chemistry (J Biol Chem) Vol. 289 Issue 8 Pg. 5228-39 (Feb 21 2014) ISSN: 1083-351X [Electronic] United States
• PMID: 24379404 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• Bacterial Proteins
• Disulfides
• Glycopeptides
• mycothiol
• Inositol
• NADP
• Hydrogen Peroxide
• Peroxiredoxins
• Cysteine

Topics

• Bacterial Proteins (metabolism)
• Biocatalysis (drug effects)
• Cysteine (chemistry, metabolism)
• Disulfides (metabolism)
• Glycopeptides (chemistry, metabolism)
• Hydrogen Peroxide (pharmacology)
• Hydrogen-Ion Concentration (drug effects)
• Inositol (chemistry, metabolism)
• Kinetics
• Models, Biological
• Mycobacterium tuberculosis (metabolism)
• NADP (metabolism)
• Oxidation-Reduction (drug effects)
• Peroxiredoxins (metabolism)