title: PrxQ-A, a member of the peroxiredoxin Q family, plays a major role in defense against oxidative stress in the cyanobacterium Anabaena sp. strain PCC7120.
abstract: The genome of the cyanobacterium Anabaena PCC 7120 encodes seven polypeptides showing sequence similarities with peroxiredoxins (Prx-s). One of them, prxQ-A (alr2503), which encodes a Prx Q homologue, is located in the same gene cluster as pkn22, which encodes a Ser/Thr kinase. Here we report that the pkn22-knockout mutant (Mp22) is sensitive to oxidative stress because it fails to synthesize PrxQ-A; the expression of prxQ-A is significantly induced under oxidative stress conditions. The hypersensitivity of the Mp22 mutant to oxidative stress was restored by inducing the expression of the prxQ-A gene in trans. The recombinant PrxQ-A protein shows antioxidant activity protecting the DNA from being degraded by reactive oxygen species, catalyzes the reduction of H2O2 in the presence of DTT, and shows thioredoxin-dependent peroxidase activity in vitro. The conserved Cys47 residue is the peroxide oxidation site, since the replacement of Cys47 by a Ser residue completely abolished the peroxidase activity. All these data suggest that PrxQ-A may efficiently protect this organism from oxidative stress.
authors.affiliation: Laboratoire de Chimie Bactérienne, IBSM-CNRS, 31 Chemin Joseph Aiguier, 13402 Marseille cedex 20, France. latifi@ibsm.cnrs-mrs.fr
authors.forename: Amel
authors.initials: A
authors.lastname: Latifi
authors.forename: Marion
authors.initials: M
authors.lastname: Ruiz
authors.forename: Robert
authors.initials: R
authors.lastname: Jeanjean
authors.forename: Cheng-Cai
authors.initials: CC
authors.lastname: Zhang
mesh_terms: D000595:Amino Acid Sequence; D017033:Anabaena / Q000235:genetics / Q000378:metabolism*; D000975:Antioxidants / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D004249:DNA Damage; D004229:Dithiothreitol / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D018384:Oxidative Stress; D010544:Peroxidases / Q000235:genetics / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism; D013879:Thioredoxins / Q000378:metabolism
chemical_list: D000975:Antioxidants; D001426:Bacterial Proteins; D017382:Reactive Oxygen Species; D013879:Thioredoxins; D006861:Hydrogen Peroxide; D010544:Peroxidases; D004229:Dithiothreitol