title: Crystal structure of alkyl hydroperoxide-reductase (AhpC) from Helicobacter pylori.
abstract: The AhpC protein from H. pylori, a thioredoxin (Trx)-dependent alkyl hydroperoxide-reductase, is a member of the ubiquitous 2-Cys peroxiredoxins family (2-Cys Prxs), a group of thiol-specific antioxidant enzymes. Prxs exert the protective antioxidant role in cells through their peroxidase activity, whereby hydrogen peroxide, peroxynitrite and a wide range of organic hydroperoxides (ROOH) are reduced and detoxified (ROOH + 2e(-)-->ROH + H2O). In this study AhpC has been cloned and overexpressed in E. coli. After purification to homogeneity, crystals of the recombinant protein were grown. They diffract to 2.95 A resolution using synchrotron radiation. The crystal structure of AhpC has been determined using the molecular replacement method (R = 23.6%, R(free) = 25.9%). The model, similar in the overall to other members of the 2-Cys Prx family crystallized as toroide-shaped complexes, consists of a pentameric arrangement of homodimers [(alpha2)5 decamer]. The model of AhpC from H. pylori presents significant differences with respect to other members of the family: apart from some loop regions, alpha5-helix and the C-terminus is shifted, preventing the C-terminal tail of the second subunit from extending toward this region of the molecule. Oligomerization properties of AhpC have been also characterized by gel filtration chromatography.
authors.affiliation: Department of Chemical Sciences, University of Padua, and ICTB, Via Marzolo 1, and Venetian Institute of Molecular Medicine, Via Orus 2, Padua, Italy.
authors.forename: Elena
authors.initials: E
authors.lastname: Papinutto
authors.forename: Henry J
authors.initials: HJ
authors.lastname: Windle
authors.forename: Laura
authors.initials: L
authors.lastname: Cendron
authors.forename: Roberto
authors.initials: R
authors.lastname: Battistutta
authors.forename: Dermot
authors.initials: D
authors.lastname: Kelleher
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Zanotti
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D018360:Crystallography, X-Ray; D019281:Dimerization; D016480:Helicobacter pylori / Q000201:enzymology*; D008958:Models, Molecular; D010544:Peroxidases / Q000737:chemistry* / Q000378:metabolism; D010545:Peroxides / Q000378:metabolism; D054464:Peroxiredoxins; D030421:Peroxynitrous Acid / Q000378:metabolism; D020836:Protein Structure, Quaternary
chemical_list: D001426:Bacterial Proteins; D010545:Peroxides; D030421:Peroxynitrous Acid; D010544:Peroxidases; D054464:Peroxiredoxins