title: Mycoredoxin-1 is one of the missing links in the oxidative stress defence mechanism of Mycobacteria.
abstract: To survive hostile conditions, the bacterial pathogen Mycobacterium tuberculosis produces millimolar concentrations of mycothiol as a redox buffer against oxidative stress. The reductases that couple the reducing power of mycothiol to redox active proteins in the cell are not known. We report a novel mycothiol-dependent reductase (mycoredoxin-1) with a CGYC catalytic motif. With mycoredoxin-1 and mycothiol deletion strains of Mycobacterium smegmatis, we show that mycoredoxin-1 and mycothiol are involved in the protection against oxidative stress. Mycoredoxin-1 acts as an oxidoreductase exclusively linked to the mycothiol electron transfer pathway and it can reduce S-mycothiolated mixed disulphides. Moreover, we solved the solution structures of oxidized and reduced mycoredoxin-1, revealing a thioredoxin fold with a putative mycothiol-binding site. With HSQC snapshots during electron transport, we visualize the reduction of oxidized mycoredoxin-1 as a function of time and find that mycoredoxin-1 gets S-mycothiolated on its N-terminal nucleophilic cysteine. Mycoredoxin-1 has a redox potential of -218 mV and hydrogen bonding with neighbouring residues lowers the pKa of its N-terminal nucleophilic cysteine. Determination of the oxidized and reduced structures of mycoredoxin-1, better understanding of mycothiol-dependent reactions in general, will likely give new insights in how M. tuberculosis survives oxidative stress in human macrophages.
authors.affiliation: Department of Structural Biology, Vlaams Instituut voor Biotechnologie, Brussels, 1050, Belgium.
authors.forename: Koen
authors.initials: K
authors.lastname: Van Laer
authors.forename: Lieven
authors.initials: L
authors.lastname: Buts
authors.forename: Nicolas
authors.initials: N
authors.lastname: Foloppe
authors.forename: Didier
authors.initials: D
authors.lastname: Vertommen
authors.forename: Karolien
authors.initials: K
authors.lastname: Van Belle
authors.forename: Khadija
authors.initials: K
authors.lastname: Wahni
authors.forename: Goedele
authors.initials: G
authors.lastname: Roos
authors.forename: Lennart
authors.initials: L
authors.lastname: Nilsson
authors.forename: Luis M
authors.initials: LM
authors.lastname: Mateos
authors.forename: Mamta
authors.initials: M
authors.lastname: Rawat
authors.forename: Nico A J
authors.initials: NA
authors.lastname: van Nuland
authors.forename: Joris
authors.initials: J
authors.lastname: Messens
mesh_terms: D003545:Cysteine / Q000378:metabolism*; D004220:Disulfides / Q000378:metabolism; D017353:Gene Deletion; D006020:Glycopeptides / Q000378:metabolism*; D007294:Inositol / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D020102:Mycobacterium smegmatis / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D010088:Oxidoreductases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011487:Protein Conformation
chemical_list: D004220:Disulfides; D006020:Glycopeptides; C089265:mycothiol; D007294:Inositol; D010088:Oxidoreductases; D003545:Cysteine