title: Crystal structure of decameric 2-Cys peroxiredoxin from human erythrocytes at 1.7 A resolution.
abstract: BACKGROUND
  The peroxiredoxins (Prxs) are an emerging family of multifunctional enzymes that exhibit peroxidase activity in vitro, and in vivo participate in a range of cellular processes known to be sensitive to reactive oxygen species. Thioredoxin peroxidase B (TPx-B), a 2-Cys type II Prx from erythrocytes, promotes potassium efflux and down-regulates apoptosis and the recruitment of monocytes by endothelial tissue.
  
  
  RESULTS
  The crystal structure of human decameric TPx-B purified from erythrocytes has been determined to 1.7 [corrected)] A resolution. The structure is a toroid comprising five dimers linked end-on through predominantly hydrophobic interactions, and is proposed to represent an intermediate in the in vivo reaction cycle. In the crystal structure, Cys51, the site of peroxide reduction, is oxidised to cysteine sulphinic acid. The residue Cys172, lies approximately 10 A away from Cys51 [corrected].
  
  
  CONCLUSIONS
  The oxidation of Cys51 appears to have trapped the structure into a stable decamer, as confirmed by sedimentation analysis. A comparison with two previously reported dimeric Prx structures reveals that the catalytic cycle of 2-Cys Prx requires significant conformational changes that include the unwinding of the active-site helix and the movement of four loops. It is proposed that the stable decamer forms in vivo under conditions of oxidative stress. Similar decameric structures of TPx-B have been observed by electron microscopy, which show the protein associated with the erythrocyte membrane.
authors.affiliation: Schools of Chemistry and Biological Sciences, University of Exeter, Exeter, EX4 4QD, UK. eschrode@ex.ac.uk
authors.forename: E
authors.initials: E
authors.lastname: Schröder
authors.forename: J A
authors.initials: JA
authors.lastname: Littlechild
authors.forename: A A
authors.initials: AA
authors.lastname: Lebedev
authors.forename: N
authors.initials: N
authors.lastname: Errington
authors.forename: A A
authors.initials: AA
authors.lastname: Vagin
authors.forename: M N
authors.initials: MN
authors.lastname: Isupov
mesh_terms: D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D004912:Erythrocytes / Q000201:enzymology; D004913:Erythrocytes, Abnormal / Q000201:enzymology; D006801:Humans; D008958:Models, Molecular; D009363:Neoplasm Proteins; D010544:Peroxidases / Q000097:blood / Q000737:chemistry*; D061105:Peroxiredoxin III; D054464:Peroxiredoxins; D011487:Protein Conformation; D020836:Protein Structure, Quaternary; D055672:Static Electricity
chemical_list: D009363:Neoplasm Proteins; D010544:Peroxidases; C516115:PRDX3 protein, human; D061105:Peroxiredoxin III; D054464:Peroxiredoxins