Fe3+-hydroxide ligation in the superoxide reductase from Desulfoarculus baarsii is associated with pH dependent spectral changes.

Abstract : Superoxide reductase (SOR) catalyzes the reduction of O2*- to H2O2. Its active site consists of a non-heme Fe2+ center in an unusual square-pyramidal [His4 Cys] coordination. Like many SORs, the electronic absorption band corresponding to the oxidized active site of the SOR from Desulfoarculus baarsii exhibits a pH-dependent alkaline transition changing from ca. 644 to 560 nm as the pH increases and with an apparent pKa of 9.0. Variants in which the conserved amino acids glutamate 47 and lysine 48 were replaced by the neutral residues alanine (E47A) and isoleucine (K48I), respectively, exhibited the same alkaline transition but at lower apparent pKa values of 6.7 and 7.6, respectively. Previous work [Nivière, V.; Asso, M.; Weill, C. O.; Lombard, M.; Guigliarelli, B.; Favaudon, V.; Houée-Levin, C. Biochemistry 2004, 43, 808-818] has shown that this alkaline transition is associated with the protonation/deprotonation of an unidentified base, B-, which is neither E47 nor K48. In this work, we show by resonance Raman spectroscopy that at basic pH a high-spin Fe3+-OH species is formed at the active site. The presence of the HO- ligand was directly associated with an absorption band maximum at 560 nm, whereas upon protonation, the band shifts to 644 nm. With respect to our previous work, B- can be identified with this high-spin Fe3+-OH species, which upon protonation results in a water molecule at the active site. Implications for the SOR catalytic cycle are proposed.
Type de document :
Article dans une revue
Journal of the American Chemical Society, American Chemical Society, 2005, pp.16436-41
Liste complète des métadonnées

Littérature citée [14 références]  Voir  Masquer  Télécharger

http://hal.univ-grenoble-alpes.fr/hal-01075779
Contributeur : Vincent Niviere <>
Soumis le : lundi 20 octobre 2014 - 11:19:11
Dernière modification le : jeudi 28 juin 2018 - 09:50:56
Document(s) archivé(s) le : mercredi 21 janvier 2015 - 10:36:29

Fichier

MatheJACSRev.pdf
Fichiers produits par l'(les) auteur(s)

Identifiants

Collections

Citation

Christelle Mathé, Vincent Nivière, Tony A Mattioli. Fe3+-hydroxide ligation in the superoxide reductase from Desulfoarculus baarsii is associated with pH dependent spectral changes.. Journal of the American Chemical Society, American Chemical Society, 2005, pp.16436-41. 〈hal-01075779〉

Partager

Métriques

Consultations de la notice

82

Téléchargements de fichiers

89