Proc Natl Acad Sci U S A 2004 May 30;101(19):7475-80. Epub 2004 Apr 30.
Institut de Biotechnologie des Plantes, Bâtiment 630, Unité Mixte de Recherche 8618, Centre National de la Recherche Scientifique/Université Paris-Sud, F-91405 Orsay-Cedex, France.
Proteomics were used to identify the proteins from the eukaryotic unicellular green alga Chlamydomonas reinhardtii that can be reduced by thioredoxin. These proteins were retained specifically on a thioredoxin affinity column made of a monocysteinic thioredoxin mutant able to form mixed disulfides with its targets. Of a total of 55 identified targets, 29 had been found previously in higher plants or Synechocystis, but 26 were new targets. Biochemical tests were performed on three of them, showing a thioredoxin-dependent activation of isocitrate lyase and isopropylmalate dehydrogenase and a thioredoxin-dependent deactivation of catalase that is redox insensitive in Arabidopsis. In addition, we identified a Ran protein, a previously uncharacterized nuclear target in a photosynthetic organism. The metabolic and evolutionary implications of these findings are discussed.