title: Isolation and characterization of a thioredoxin-dependent peroxidase from Chlamydomonas reinhardtii.
abstract: 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.
authors.affiliation: Institut de Biotechnologie des Plantes, Université Paris-Sud, Orsay Cedex, France.
authors.forename: Aymeric
authors.initials: A
authors.lastname: Goyer
authors.forename: Camilla
authors.initials: C
authors.lastname: Haslekås
authors.forename: Myroslawa
authors.initials: M
authors.lastname: Miginiac-Maslow
authors.forename: Uwe
authors.initials: U
authors.lastname: Klein
authors.forename: Pierre
authors.initials: P
authors.lastname: Le Marechal
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Jacquot
authors.forename: Paulette
authors.initials: P
authors.lastname: Decottignies
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D016825:Chlamydomonas reinhardtii / Q000201:enzymology*; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000737:chemistry; D005786:Gene Expression Regulation; D008969:Molecular Sequence Data; D018384:Oxidative Stress; D010544:Peroxidases / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification*; D054464:Peroxiredoxins; D011994:Recombinant Proteins / Q000737:chemistry
chemical_list: D018076:DNA, Complementary; D011994:Recombinant Proteins; D010544:Peroxidases; D054464:Peroxiredoxins