Corynebacterium glutamicum survives arsenic stress with arsenate reductases coupled to two distinct redox mechanisms

• Published in: Molecular microbiology Vol. 82; no. 4; pp. 998 - 1014
• Main Authors: Villadangos, Almudena F., Van Belle, Karolien, Wahni, Khadija, Tamu Dufe, Veronica, Freitas, Sofia, Nur, Haneen, De Galan, Sandra, Gil, José A., Collet, Jean‐Francois, Mateos, Luis M., Messens, Joris
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.11.2011; Blackwell
• Subjects: Amino Acid Sequence; Arsenate Reductases - genetics; Arsenate Reductases - metabolism; Arsenic; Arsenic - metabolism; Arsenic - toxicity; Bacteria; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Bacteriology; Biological and medical sciences; Corynebacterium glutamicum; Corynebacterium glutamicum - drug effects; Corynebacterium glutamicum - enzymology; Corynebacterium glutamicum - genetics; Enzyme kinetics; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Bacterial; Gene Expression Regulation, Enzymologic; Gene Knockout Techniques; Genes; Kinetics; Metabolic Networks and Pathways - genetics; Microbiology; Miscellaneous; Models, Biological; Models, Molecular; Molecular Sequence Data; Oxidation-Reduction; Protein Conformation; Protein Multimerization; Proteins; Sequence Homology, Amino Acid; Stress, Physiological; Arsenic; Arsenates; Enzyme; Corynebacterium glutamicum; Bacteria; Actinomycetes; Corynebacteriaceae; Oxidoreductases; Mechanism; Stress; Heavy metal; Reductase
• ISSN: 0950-382X; 1365-2958
• DOI: 10.1111/j.1365-2958.2011.07882.x

Summary Arsenate reductases (ArsCs) evolved independently as a defence mechanism against toxic arsenate. In the genome of Corynebacterium glutamicum, there are two arsenic resistance operons (ars1 and ars2) and four potential genes coding for arsenate reductases (Cg_ArsC1, Cg_ArsC2, Cg_ArsC1' and Cg_ArsC4). Using knockout mutants, in vitro reconstitution of redox pathways, arsenic measurements and enzyme kinetics, we show that a single organism has two different classes of arsenate reductases. Cg_ArsC1 and Cg_ArsC2 are single‐cysteine monomeric enzymes coupled to the mycothiol/mycoredoxin redox pathway using a mycothiol transferase mechanism. In contrast, Cg_ArsC1' is a three‐cysteine containing homodimer that uses a reduction mechanism linked to the thioredoxin pathway with a kcat/KM value which is 103 times higher than the one of Cg_ArsC1 or Cg_ArsC2. Cg_ArsC1' is constitutively expressed at low levels using its own promoter site. It reduces arsenate to arsenite that can then induce the expression of Cg_ArsC1 and Cg_ArsC2. We also solved the X‐ray structures of Cg_ArsC1' and Cg_ArsC2. Both enzymes have a typical low‐molecular‐weight protein tyrosine phosphatases‐I fold with a conserved oxyanion binding site. Moreover, Cg_ArsC1' is unique in bearing an N‐terminal three‐helical bundle that interacts with the active site of the other chain in the dimeric interface.