| Redox regulation by glutathionylation and glutaredoxins in Chlamydomonas |
| Stéphane D. Lemaire1, Laure Michelet1,5, Mirko Zaffagnini1, Hélène Vanacker1, Michael Schroda3, Paolo Trost4, Paulette Decottignies2. |
| 1Institut de Biotechnologie des Plantes, UMR 8618, CNRS/Univ. Paris-Sud, Orsay, France 2UMR 8619/IFR 46, CNRS/Univ. Paris-Sud, Orsay, France; 3 University of Freiburg, Germany; 4Univ. of Bologna, Italy 5Present address: Univ. of Geneva, Switzerland |
| Glutathione plays multiple roles in the physiological response of plants to oxidative stress and is implicated in a reversible post-translational modification, named S-glutathionylation, consisting of the formation of a mixed disulfide between a protein thiol and a molecule of glutathione. We have recently shown that thioredoxin f (1) and A4-glyceraldehyde-3-phosphate dehydrogenase (2) from Arabidopsis, two chloroplastic proteins playing a major role in carbon assimilation, can be regulated by glutathionylation in vitro. In order to get more insight into the proteins regulated by glutathionylation n vivo, we developed a proteomic approach based on [35S]-cysteine labeling of the glutathione pool in Chlamydomonas reinhardtii. Proteins radiolabeled after oxidative stress treatments were visualized on 2D-gels and identified by mass spectrometry. This method allowed identification of a number of glutathionylated proteins, most of which are located in chloroplasts. Glutathionylation of three of these targets was confirmed in vitro on recombinant proteins. We have also examined the ability of GRXs from Chlamydomonas reinhardtii to catalyze deglutathionylation reactions. Cytosolic GRX1 exhibited properties similar to those previously described for GRX from other organisms. On the other hand, chloroplastic GRX3 exhibited unique properties, notably, the ability to be very efficiently reduced in the light by ferredoxin thioredoxin reductase (3).
(1) Michelet et al. (2005) Proc. Natl. Acad. Sci. USA, 102, 16478-16483. |
| e-mail address of presenting author: stephane.lemaire@u-psud.fr |