title: A structural analysis of the catalytic mechanism of methionine sulfoxide reductase A from Neisseria meningitidis.
abstract: The methionine sulfoxide reductases (Msrs) are thioredoxin-dependent oxidoreductases that catalyse the reduction of the sulfoxide function of the oxidized methionine residues. These enzymes have been shown to regulate the life span of a wide range of microbial and animal species and to play the role of physiological virulence determinant of some bacterial pathogens. Two structurally unrelated classes of Msrs exist, MsrA and MsrB, with opposite stereoselectivity towards the R and S isomers of the sulfoxide function, respectively. Both Msrs share a similar three-step chemical mechanism including (1) the formation of a sulfenic acid intermediate on the catalytic Cys with the concomitant release of the product-methionine, (2) the formation of an intramonomeric disulfide bridge between the catalytic and the regenerating Cys and (3) the reduction of the disulfide bridge by thioredoxin or its homologues. In this study, four structures of the MsrA domain of the PilB protein from Neisseria meningitidis, representative of four catalytic intermediates of the MsrA catalytic cycle, were determined by X-ray crystallography: the free reduced form, the Michaelis-like complex, the sulfenic acid intermediate and the disulfide oxidized forms. They reveal a conserved overall structure up to the formation of the sulfenic acid intermediate, while a large conformational switch is observed in the oxidized form. The results are discussed in relation to those proposed from enzymatic, NMR and theoretical chemistry studies. In particular, the substrate specificity and binding, the catalytic scenario of the reductase step and the relevance and role of the large conformational change observed in the oxidized form are discussed.
authors.affiliation: LCM3B, Equipe Biocristallographie, UMR 7036 CNRS-UHP, Faculté des Sciences et Techniques, Nancy Université, BP 239, 54506 Vandoeuvre-les-Nancy, France.
authors.forename: Fanomezana M
authors.initials: FM
authors.lastname: Ranaivoson
authors.forename: Mathias
authors.initials: M
authors.lastname: Antoine
authors.forename: Brice
authors.initials: B
authors.lastname: Kauffmann
authors.forename: Sandrine
authors.initials: S
authors.lastname: Boschi-Muller
authors.forename: André
authors.initials: A
authors.lastname: Aubry
authors.forename: Guy
authors.initials: G
authors.lastname: Branlant
authors.forename: Frédérique
authors.initials: F
authors.lastname: Favier
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002384:Catalysis; D003545:Cysteine; D051150:Methionine Sulfoxide Reductases; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009345:Neisseria meningitidis / Q000201:enzymology*; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000737:chemistry* / Q000378:metabolism*; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D012996:Solutions; D013379:Substrate Specificity
chemical_list: D012996:Solutions; D010088:Oxidoreductases; D051150:Methionine Sulfoxide Reductases; C027219:methionine sulfoxide reductase; D003545:Cysteine