Biochemical characterization of glutaredoxins from Chlamydomonas reinhardtii reveals the unique properties of a chloroplastic CGFS-type glutaredoxin.
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 approximately 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 A(4)-glyceraldehyde-3-phosphate dehydrogenase deglutathionylation, whereas cytosolic and chloroplastic thioredoxins were inefficient. Glutathionylated A(4)-glyceraldehyde-3-phosphate dehydrogenase is the first physiological substrate identified for a CGFS-type GRX.
Zaffagnini
Mirko
M
Institut de Biotechnologie des Plantes, UMR 8618, CNRS/University of Paris-Sud 11, Bâtiment 630, Orsay 91405, Cedex, France.
Michelet
Laure
L
Massot
Vincent
V
Trost
Paolo
P
Lemaire
Stéphane D
SD
D020418:Algal Proteins / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D016825:Chlamydomonas reinhardtii / Q000201:enzymology*; D002736:Chloroplasts / Q000201:enzymology*; D003593:Cytoplasm / Q000201:enzymology*; D005288:Ferredoxins / Q000737:chemistry / Q000378:metabolism; D054477:Glutaredoxins / Q000737:chemistry / Q000378:metabolism*; D005978:Glutathione / Q000737:chemistry / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007506:Iron-Sulfur Proteins / Q000737:chemistry / Q000378:metabolism; D007527:Isoenzymes / Q000737:chemistry / Q000378:metabolism; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000737:chemistry / Q000378:metabolism; D015800:Protozoan Proteins / Q000737:chemistry / Q000378:metabolism*; D013379:Substrate Specificity
D020418:Algal Proteins; D005288:Ferredoxins; D054477:Glutaredoxins; D007506:Iron-Sulfur Proteins; D007527:Isoenzymes; D015800:Protozoan Proteins; D010088:Oxidoreductases; C021588:ferredoxin-thioredoxin reductase; C020666:glutathione dehydrogenase (ascorbate); D005978:Glutathione