TAILIEUCHUNG - Báo cáo khoa học: Thioredoxin Ch1 of Chlamydomonas reinhardtii displays an unusual resistance toward one-electron oxidation

To test thioredoxin resistance to oxidizing free radicals, we have studied the one-electron oxidation of wild-type thio-redoxin and of two forms with the point mutations D30A and W35A, using azide radicals generated byc-ray or pulse radiolysis. The oxidation patterns of wild-type thioredoxin and D30A are similar. In these forms, Trp35 is the primary target and is repaired by one-electron reduction; first by intramolecular electron transfer from tyrosine, and then fromother residues. Conversely, duringoxidationofW35A, Trp13 is poorly reactive. For all proteins, activity is con-served showing an unusual resistance toward oxidation | Eur. J. Biochem. 271 3481-3487 2004 FEBS 2004 doi Thioredoxin Ch1 of Chlamydomonasreinhardtii displays an unusual resistance toward one-electron oxidation Cecile Sicard-Roselli1 Stephane Lemaire2 Jean-Pierre Jacquot3 Vincent Favaudon4 Christophe Marchand5 and Chantal Houée-Levin1 1 Laboratoire de Chimie Physique and 2Institut de Biotechnologie des Plantes Universite Paris XI Orsay France 2UMR 1136 Interaction Arbres Microorganismes INRA UHP Universite de Nancy I Vandoeuvre France 4U 612 INSERM Institut Curie Centre Universitaire Orsay France 5Institut de Biochimie et Biophysique Moleculaire et Cellulaire CNRS UMR8619 and IFR46 Universite Paris XI Orsay France To test thioredoxin resistance to oxidizing free radicals we have studied the one-electron oxidation of wild-type thioredoxin and of two forms with the point mutations D30A and W35A using azide radicals generated by y-ray or pulse radiolysis. The oxidation patterns of wild-type thioredoxin and D30A are similar. In these forms Trp35 is the primary target and is repaired by one-electron reduction first by intramolecular electron transfer from tyrosine and then from other residues. Conversely during oxidation of W35A Trp13 is poorly reactive. For all proteins activity is conserved showing an unusual resistance toward oxidation. Keywords thioredoxin one-electron oxidation radiolysis tryptophan35 oxidation. Thioredoxins Trx are ubiquitous small proteins 100-120 amino acids found in all living organisms from bacteria to vertebrates 1 . These proteins whose active site contains the amino acid sequence -Cys-Gly-Pro-Cys- exist either in an oxidized form with an intramolecular disulfide bond Trx-S2 or in a reduced form with two thiol functions Trx- SH 2 . They are involved in the reduction of disufide bonds and play a major role in the control of intracellular reduction potential and defense against oxidative stress. In addition these proteins control the release of transcription factors

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