title: Regeneration mechanisms of Arabidopsis thaliana methionine sulfoxide reductases B by glutaredoxins and thioredoxins.
abstract: Methionine oxidation leads to the formation of S- and R-diastereomers of methionine sulfoxide (MetSO), which are reduced back to methionine by methionine sulfoxide reductases (MSRs) A and B, respectively. MSRBs are classified in two groups depending on the conservation of one or two redox-active Cys; 2-Cys MSRBs possess a catalytic Cys-reducing MetSO and a resolving Cys, allowing regeneration by thioredoxins. The second type, 1-Cys MSRBs, possess only the catalytic Cys. The biochemical mechanisms involved in activity regeneration of 1-Cys MSRBs remain largely elusive. In the present work we used recombinant plastidial Arabidopsis thaliana MSRB1 and MSRB2 as models for 1-Cys and 2-Cys MSRBs, respectively, to delineate the Trx- and glutaredoxin-dependent reduction mechanisms. Activity assays carried out using a series of cysteine mutants and various reductants combined with measurements of free thiols under distinct oxidation conditions and mass spectrometry experiments show that the 2-Cys MSRB2 is reduced by Trx through a dithiol-disulfide exchange involving both redox-active Cys of the two partners. Regarding 1-Cys MSRB1, oxidation of the enzyme after substrate reduction leads to the formation of a stable sulfenic acid on the catalytic Cys, which is subsequently glutathionylated. The deglutathionylation of MSRB1 is achieved by both mono- and dithiol glutaredoxins and involves only their N-terminal conserved catalytic Cys. This study proposes a detailed mechanism of the regeneration of 1-Cys MSRB activity by glutaredoxins, which likely constitute physiological reductants for this type of MSR.
authors.affiliation: Commissariat à l'Energie Atomique (Cadarache, France), Direction des Sciences du Vivant, Institut de Biologie Environnementale et Biotechnologie, Laboratoire d'Ecophysiologie Moléculaire des Plantes, 13108 Saint-Paul-lez-Durance Cedex, France.
authors.forename: Lionel
authors.initials: L
authors.lastname: Tarrago
authors.forename: Edith
authors.initials: E
authors.lastname: Laugier
authors.forename: Mirko
authors.initials: M
authors.lastname: Zaffagnini
authors.forename: Christophe
authors.initials: C
authors.lastname: Marchand
authors.forename: Pierre
authors.initials: P
authors.lastname: Le Maréchal
authors.forename: Nicolas
authors.initials: N
authors.lastname: Rouhier
authors.forename: Stéphane D
authors.initials: SD
authors.lastname: Lemaire
authors.forename: Pascal
authors.initials: P
authors.lastname: Rey
mesh_terms: D017360:Arabidopsis / Q000378:metabolism*; D002384:Catalysis; D003545:Cysteine / Q000737:chemistry; D054477:Glutaredoxins / Q000378:metabolism*; D005978:Glutathione / Q000737:chemistry; D007700:Kinetics; D051150:Methionine Sulfoxide Reductases; D008954:Models, Biological; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010088:Oxidoreductases / Q000737:chemistry*; D018521:Plant Physiological Phenomena; D017434:Protein Structure, Tertiary; D012038:Regeneration; D013438:Sulfhydryl Compounds / Q000737:chemistry; D013879:Thioredoxins / Q000737:chemistry*
chemical_list: D054477:Glutaredoxins; D013438:Sulfhydryl Compounds; D013879:Thioredoxins; D010088:Oxidoreductases; D051150:Methionine Sulfoxide Reductases; C027219:methionine sulfoxide reductase; D005978:Glutathione; D003545:Cysteine