Regeneration Mechanisms of Arabidopsis thaliana Methionine Sulfoxide Reductases B by Glutaredoxins and Thioredoxins
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...
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Published in | The Journal of biological chemistry Vol. 284; no. 28; pp. 18963 - 18971 |
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Main Authors | , , , , , , , |
Format | Journal Article |
Language | English |
Published |
United States
Elsevier Inc
10.07.2009
American Society for Biochemistry and Molecular Biology |
Subjects | |
Online Access | Get full text |
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Summary: | 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. |
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Bibliography: | Present address: Institut de Biologie Intégrative des Plantes, Unité Mixte de Recherche 5004, Biochimie et Physiologie Moléculaire des Plantes, Agro-M/CNRS/INRA/UM2, Place Viala, 34060 Montpellier Cedex, France. |
ISSN: | 0021-9258 1083-351X |
DOI: | 10.1074/jbc.M109.015487 |