title: Characterization of plant sulfiredoxin and role of sulphinic form of 2-Cys peroxiredoxin.
abstract: The antioxidant function of 2-Cys peroxiredoxin (Prx) involves the oxidation of its conserved peroxidatic cysteine to sulphenic acid that is recycled by a reductor agent. In conditions of oxidative stress, the peroxidatic cysteine can be overoxidized to sulphinic acid inactivating the Prx. An enzyme recently discovered, named sulfiredoxin (Srx), reduces the sulphinic 2-Cys Prx (Prx-SO(2)H). To explore the physiological functions of Srx in plants we have cloned, expressed and purified to homogeneity a Srx from Arabidopsis thaliana (AtSrx), as well as five variants by site-directed mutagenesis on amino acids involved in its activity. The activity of sulfiredoxin, determined by a new method, is dependent on the concentration of the sulphinic form of Prx and the conserved Srx is capable of regenerating the functionality of both pea and Arabidopsis Prx-SO(2)H. Molecular modelling of AtSrx and the facts that the R28Q variant shows a partial inactivation, that the activity of the E76A variant is equivalent to that of the native enzyme and that the double mutation R28Q/E76A abolishes the enzymatic activity suggests that the pair His100-Glu76 may be involved in the activation of C72 in the absence of R28. The knock-out mutant plants without Srx or 2-Cys Prx exhibited phenotypical differences under growth conditions of 16 h light, probably due to the signalling role of the sulphinic form of Prx. These mutants showed more susceptibility to oxidative stress than wild-type plants. This work presents the first systematic biochemical characterization of the Srx/Prx system from plants and contributes to a better understanding of its physiological function.
authors.affiliation: Department of Biochemistry and Cellular and Molecular Biology of Plants, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, C/Profesor Albareda 1, E-18008 Granada, Spain.
authors.forename: Iván
authors.initials: I
authors.lastname: Iglesias-Baena
authors.forename: Sergio
authors.initials: S
authors.lastname: Barranco-Medina
authors.forename: Alfonso
authors.initials: A
authors.lastname: Lázaro-Payo
authors.forename: Francisco Javier
authors.initials: FJ
authors.lastname: López-Jaramillo
authors.forename: Francisca
authors.initials: F
authors.lastname: Sevilla
authors.forename: Juan-José
authors.initials: JJ
authors.lastname: Lázaro
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D015153:Blotting, Western; D004591:Electrophoresis, Polyacrylamide Gel; D006861:Hydrogen Peroxide / Q000378:metabolism; D007700:Kinetics; D016297:Mutagenesis, Site-Directed; D050862:Oxidoreductases Acting on Sulfur Group Donors / Q000235:genetics / Q000378:metabolism*; D018532:Pisum sativum / Q000235:genetics / Q000378:metabolism; D054464:Peroxiredoxins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D016133:Polymerase Chain Reaction
chemical_list: D029681:Arabidopsis Proteins; D006861:Hydrogen Peroxide; D054464:Peroxiredoxins; D050862:Oxidoreductases Acting on Sulfur Group Donors; C520419:sulfiredoxin protein, Arabidopsis