title: A sulfenic acid enzyme intermediate is involved in the catalytic mechanism of peptide methionine sulfoxide reductase from Escherichia coli.
abstract: Methionine oxidation into methionine sulfoxide is known to be involved in many pathologies and to exert regulatory effects on proteins. This oxidation can be reversed by a ubiquitous monomeric enzyme, the peptide methionine sulfoxide reductase (MsrA), whose activity in vivo requires the thioredoxin-regenerating system. The proposed chemical mechanism of Escherichia coli MsrA involves three Cys residues (positions 51, 198, and 206). A fourth Cys (position 86) is not important for catalysis. In the absence of a reducing system, 2 mol of methionine are formed per mole of enzyme for wild type and Cys-86 --> Ser mutant MsrA, whereas only 1 mol is formed for mutants in which either Cys-198 or Cys-206 is mutated. Reduction of methionine sulfoxide is shown to proceed through the formation of a sulfenic acid intermediate. This intermediate has been characterized by chemical probes and mass spectrometry analyses. Together, the results support a three-step chemical mechanism in vivo: 1) Cys-51 attacks the sulfur atom of the sulfoxide substrate leading, via a rearrangement, to the formation of a sulfenic acid intermediate on Cys-51 and release of 1 mol of methionine/mol of enzyme; 2) the sulfenic acid is then reduced via a double displacement mechanism involving formation of a disulfide bond between Cys-51 and Cys-198, followed by formation of a disulfide bond between Cys-198 and Cys-206, which liberates Cys-51, and 3) the disulfide bond between Cys-198 and Cys-206 is reduced by thioredoxin-dependent recycling system process.
authors.affiliation: UMR CNRS-UHP 7567, Maturation des ARN et Enzymologie Moléculaire, Faculté des Sciences, Bld des Aiguillettes, BP 239, 54506 Vandoeuvre-les-Nancy, France.
authors.forename: S
authors.initials: S
authors.lastname: Boschi-Muller
authors.forename: S
authors.initials: S
authors.lastname: Azza
authors.forename: S
authors.initials: S
authors.lastname: Sanglier-Cianferani
authors.forename: F
authors.initials: F
authors.lastname: Talfournier
authors.forename: A
authors.initials: A
authors.lastname: Van Dorsselear
authors.forename: G
authors.initials: G
authors.lastname: Branlant
mesh_terms: D001665:Binding Sites; D002384:Catalysis; D003545:Cysteine / Q000737:chemistry / Q000378:metabolism; D004220:Disulfides / Q000737:chemistry / Q000378:metabolism; D004228:Dithionitrobenzoic Acid; D004229:Dithiothreitol / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D008715:Methionine / Q000031:analogs & derivatives / Q000378:metabolism; D051150:Methionine Sulfoxide Reductases; D008956:Models, Chemical; D008970:Molecular Weight; D009154:Mutation; D010088:Oxidoreductases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010455:Peptides / Q000737:chemistry / Q000378:metabolism*; D019163:Reducing Agents / Q000032:analysis; D021241:Spectrometry, Mass, Electrospray Ionization; D013434:Sulfenic Acids / Q000737:chemistry / Q000378:metabolism*; D013438:Sulfhydryl Compounds / Q000032:analysis; D013879:Thioredoxins / Q000378:metabolism
chemical_list: D004220:Disulfides; D010455:Peptides; D019163:Reducing Agents; D013434:Sulfenic Acids; D013438:Sulfhydryl Compounds; D013879:Thioredoxins; D004228:Dithionitrobenzoic Acid; D008715:Methionine; D010088:Oxidoreductases; D051150:Methionine Sulfoxide Reductases; C027219:methionine sulfoxide reductase; D003545:Cysteine; D004229:Dithiothreitol; C013111:methionine sulfoxide