TAILIEUCHUNG - Báo cáo Y học: Isolation and characterization of a thioredoxin-dependent peroxidase from Chlamydomonas reinhardtii

All living organisms contain redox systems involving thior-edoxins (Trx), proteins featuringanextremelyconservedand reactive active site that perform thiol-disul®de interchanges with disul®de bridges of target proteins. In photosynthetic organisms, numerous isoforms of Trx coexist, as revealedby sequencing ofArabidopsisgenome. The speci®c functions of many of them are still unknown. | Eur. J. Biochem. 269 272-282 2002 FEBS 2002 Isolation and characterization of a thioredoxin-dependent peroxidase from Chlamydomonas reinhardtii Avmeric Gover1 Camilla Haslekas2 Mvroslawa Miainiac-Maslow1 Uwe Klein2 Pierre Le Marechal3 Jean-Pierre Jacquot4 and Paulette Decottignies3 1Institut de Biotechnologie des Plantes Universite Paris-Sud Orsay Cedex France department of Biology Division of Molecular Biology University of Oslo Blindern Oslo Norway 3IBBMC Universite Paris-Sud Orsay Cedex France Interaction Arbres-Microorganismes INRA Universite Nancy Vandoeuvre Cedex France All living organisms contain redox systems involving thioredoxins Trx proteins featuring an extremely conserved and reactive active site that perform thiol-disulfide interchanges with disulfide bridges of target proteins. In photosynthetic organisms numerous isoforms of Trx coexist as revealed by sequencing of Arabidopsis genome. The specific functions of many of them are still unknown. In an attempt to find new molecular targets of Trx in Chlamydomonas reinhardtii an affinity column carrying a cytosolic Trx h mutated at the less reactive cysteine of its active site was used to trap Chlamydomonas proteins that form mixed disulfides with Trx. The major protein bound to the column was identified by amino-acid sequencing and mass spectrometry as a thioredoxin-dependent 2Cys peroxidase. Isolation and sequencing of its gene revealed that this peroxidase is most likely a chloroplast protein with a high homology to plant 2Cys peroxiredoxins. It is shown that the Chlamydomonas peroxiredoxin Ch-Prx1 is active with various thioredoxin isoforms functions as an antioxidant toward reactive oxygen species ROS and protects DNA against ROS-induced degradation. Expression of the peroxidase gene in Chlamydomonas was found to be regulated by light oxygen concentration and redox state. The data suggest a role for the Chlamydomonas Prx in ROS detoxification in the chloroplast. Keywords Chlamydomonas peroxiredoxin

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