title: Kinetic characterization of the chemical steps involved in the catalytic mechanism of methionine sulfoxide reductase A from Neisseria meningitidis.
abstract: Oxidation of methionine into methionine sulfoxide is associated with many pathologies and is described to exert regulatory effects on protein functions. Two classes of methionine sulfoxide reductases, called MsrA and MsrB, have been described to reduce the S and the R isomers of the sulfoxide of methionine sulfoxide back to methionine, respectively. Although MsrAs and MsrBs display quite different x-ray structures, they share a similar, new catalytic mechanism that proceeds via the sulfenic acid chemistry and that includes at least three chemical steps with 1) the formation of a sulfenic acid intermediate and the concomitant release of methionine; 2) the formation of an intra-disulfide bond; and 3) the reduction of the disulfide bond by thioredoxin. In the present study, it is shown that for the Neisseria meningitidis MsrA, 1) the rate-limiting step is associated with the reduction of the Cys-51/Cys-198 disulfide MsrA bond by thioredoxin; 2) the formation of the sulfenic acid intermediate is very efficient, thus suggesting catalytic assistance via amino acids of the active site; 3) the rate-determining step in the formation of the Cys-51/Cys-198 disulfide bond is that leading to the formation of the sulfenic intermediate on Cys-51; and 4) the apparent affinity constant for methionine sulfoxide in the methionine sulfoxide reductase step is 80-fold higher than the Km value determined under steady-state conditions.
authors.affiliation: UMR 7567 CNRS/UHP - Maturation des ARN et Enzymologie Moléculaire, Faculté des Sciences, Bld des Aiguillettes, BP 239, 54506 Vandoeuvre-les-Nancy, France.
authors.forename: Mathias
authors.initials: M
authors.lastname: Antoine
authors.forename: Sandrine
authors.initials: S
authors.lastname: Boschi-Muller
authors.forename: Guy
authors.initials: G
authors.lastname: Branlant
mesh_terms: D002384:Catalysis; D003545:Cysteine / Q000737:chemistry; D004220:Disulfides; D004305:Dose-Response Relationship, Drug; D004926:Escherichia coli / Q000378:metabolism; D007700:Kinetics; D008715:Methionine / Q000031:analogs & derivatives* / Q000737:chemistry*; D051150:Methionine Sulfoxide Reductases; D008956:Models, Chemical; D016297:Mutagenesis, Site-Directed; D009345:Neisseria meningitidis / Q000201:enzymology; D010088:Oxidoreductases / Q000737:chemistry* / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D013050:Spectrometry, Fluorescence; D013434:Sulfenic Acids / Q000737:chemistry; D013696:Temperature; D013997:Time Factors
chemical_list: D004220:Disulfides; D013434:Sulfenic Acids; D008715:Methionine; D010088:Oxidoreductases; D051150:Methionine Sulfoxide Reductases; C027219:methionine sulfoxide reductase; D003545:Cysteine; D010100:Oxygen; C013111:methionine sulfoxide