title: In the absence of thioredoxins, what are the reductants for peroxiredoxins in Thermotoga maritima?
abstract: Three peroxiredoxins (Prxs) were identified in Thermotoga maritima, which possesses neither glutathione nor typical thioredoxins: one of the Prx6 class; one 2-Cys PrxBCP; and a unique hybrid protein containing an N-terminal 1-Cys PrxBCP domain fused to a flavin mononucleotide-containing nitroreductase (Ntr) domain. No peroxidase activity was detected for Prx6, whereas both bacterioferritin comigratory proteins (BCPs) were regenerated by a NADH/thioredoxin reductase/glutaredoxin (Grx)-like system, constituting a unique peroxide removal system. Only two of the three Grx-like proteins were able to support peroxidase activity. The inability of TmGrx1 to regenerate oxidized 2-Cys PrxBCP probably results from the thermodynamically unfavorable difference in their disulfide/dithiol E(m) values, -150 and -315 mV, respectively. Mutagenesis of the Prx-Ntr fusion, combined with kinetic and structural analyses, indicated that electrons are not transferred between its two domains. However, their separate activities could function in a complementary manner, with peroxide originating from the chromate reductase activity of the Ntr domain reduced by the Prx domain.
authors.affiliation: Unité Mixte de Recherches 1136 INRA-Lorraine Université, Interactions Arbres-Microorganismes, IFR 110, Faculté des Sciences, Vandoeuvre Cedex, France.
authors.forename: Jérémy
authors.initials: J
authors.lastname: Couturier
authors.forename: Pascalita
authors.initials: P
authors.lastname: Prosper
authors.forename: Alison M
authors.initials: AM
authors.lastname: Winger
authors.forename: Arnaud
authors.initials: A
authors.lastname: Hecker
authors.forename: Masakazu
authors.initials: M
authors.lastname: Hirasawa
authors.forename: David B
authors.initials: DB
authors.lastname: Knaff
authors.forename: Pierre
authors.initials: P
authors.lastname: Gans
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Jacquot
authors.forename: Alda
authors.initials: A
authors.lastname: Navaza
authors.forename: Ahmed
authors.initials: A
authors.lastname: Haouz
authors.forename: Nicolas
authors.initials: N
authors.lastname: Rouhier
mesh_terms: D002384:Catalysis; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000378:metabolism; D009195:Peroxidase / Q000378:metabolism; D054464:Peroxiredoxins / Q000737:chemistry / Q000378:metabolism*; D011487:Protein Conformation; D054730:Protein Interaction Domains and Motifs; D055503:Protein Multimerization; D019163:Reducing Agents / Q000378:metabolism*; D020124:Thermotoga maritima / Q000378:metabolism*; D013879:Thioredoxins / Q000378:metabolism*
chemical_list: D019163:Reducing Agents; D013879:Thioredoxins; D010088:Oxidoreductases; D054464:Peroxiredoxins; D009195:Peroxidase