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J. Biol. Chem., Vol. 283, Issue 14, 8868-8876, April 4, 2008
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1
From the
Institut de Biotechnologie des Plantes, UMR 8618, CNRS/University of Paris-Sud 11, Bâtiment 630, Orsay 91405, Cedex, France and the
Laboratory of Molecular Plant Physiology, Department of Experimental Evolutionary Biology, University of Bologna, Via Irnerio 42, Bologna 40126, Italy
Glutaredoxins (GRXs) are small ubiquitous disulfide oxidoreductases known to use GSH as electron donor. In photosynthetic organisms, little is known about the biochemical properties of GRXs despite the existence of
30 different isoforms in higher plants. We report here the biochemical characterization of Chlamydomonas GRX1 and GRX3, the major cytosolic and chloroplastic isoforms, respectively. Glutaredoxins are classified on the basis of the amino acid sequence of the active site. GRX1 is a typical CPYC-type GRX, which is reduced by GSH and exhibits disulfide reductase, dehydroascorbate reductase, and deglutathionylation activities. In contrast, GRX3 exhibits unique properties. This chloroplastic CGFS-type GRX is not reduced by GSH and has an atypically low redox potential (–323 ± 4 mV at pH 7.9). Remarkably, GRX3 can be reduced in the light by photoreduced ferredoxin and ferredoxin-thioredoxin reductase. Both GRXs proved to be very efficient catalysts of A4-glyceraldehyde-3-phosphate dehydrogenase deglutathionylation, whereas cytosolic and chloroplastic thioredoxins were inefficient. Glutathionylated A4-glyceraldehyde-3-phosphate dehydrogenase is the first physiological substrate identified for a CGFS-type GRX.
Received for publication, November 21, 2007 , and in revised form, January 23, 2008.
* This work was supported by the Agence Nationale de la Recherche (Grant JC-45751) and by the Italian Ministry of University (Grants FIRB 2003 and PRIN 2005). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
1 To whom correspondence should be addressed. Tel.: 33-1-69-15-33-38; Fax: 33-1-69-15-34-24; E-mail: stephane.lemaire{at}u-psud.fr.
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