Corynebacterium glutamicum survives arsenic stress with arsenate reductases coupled to two distinct redox mechanisms.
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 k(cat)/K(M) value which is 10(3) 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.
Department of Molecular Biology, Area of Microbiology, University of León, León, Spain.
Almudena F
AF
Villadangos
Karolien
K
Van Belle
Khadija
K
Wahni
Veronica Tamu
VT
Dufe
Sofia
S
Freitas
Haneen
H
Nur
Sandra
S
De Galan
José A
JA
Gil
Jean-Francois
JF
Collet
Luis M
LM
Mateos
Joris
J
Messens
D000595:Amino Acid Sequence; D053502:Arsenate Reductases / Q000235:genetics / Q000378:metabolism*; D001151:Arsenic / Q000378:metabolism / Q000633:toxicity*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D048230:Corynebacterium glutamicum / Q000187:drug effects* / Q000201:enzymology* / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D015971:Gene Expression Regulation, Enzymologic; D055786:Gene Knockout Techniques; D007700:Kinetics; D053858:Metabolic Networks and Pathways / Q000235:genetics; D008954:Models, Biological; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D011487:Protein Conformation; D055503:Protein Multimerization; D017386:Sequence Homology, Amino Acid; D013312:Stress, Physiological
D001426:Bacterial Proteins; D053502:Arsenate Reductases; D001151:Arsenic