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Role of glutaredoxin 2 and cytosolic thioredoxins in cysteinyl-based redox modification of the 20S proteasome.

The yeast 20S proteasome is subject to sulfhydryl redox alterations, such as the oxidation of cysteine residues (Cys-SH) into cysteine sulfenic acid (Cys-SOH), followed by S-glutathionylation (Cys-S-SG). Proteasome S-glutathionylation promotes partial loss of chymotrypsin-like activity and post-acidic cleavage without alteration of the trypsin-like proteasomal activity. Here we show that the 20S proteasome purified from stationary-phase cells was natively S-glutathionylated. Moreover, recombinant glutaredoxin 2 removes glutathione from natively or in vitro S-glutathionylated 20S proteasome, allowing the recovery of chymotrypsin-like activity and post-acidic cleavage. Glutaredoxin 2 deglutathionylase activity was dependent on its entry into the core particle, as demonstrated by stimulating S-glutathionylated proteasome opening. Under these conditions, deglutathionylation of the 20S proteasome and glutaredoxin 2 degradation were increased when compared to non-stimulated samples. Glutaredoxin 2 fragmentation by the 20S proteasome was evaluated by SDS-PAGE and mass spectrometry, and S-glutathionylation was evaluated by either western blot analyses with anti-glutathione IgG or by spectrophotometry with the thiol reactant 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole. It was also observed in vivo that glutaredoxin 2 was ubiquitinated in cellular extracts of yeast cells grown in glucose-containing medium. Other cytoplasmic oxido-reductases, namely thioredoxins 1 and 2, were also active in 20S proteasome deglutathionylation by a similar mechanism. These results indicate for the first time that 20S proteasome cysteinyl redox modification is a regulated mechanism coupled to enzymatic deglutathionylase activity.

Pubmed ID: 18435761


  • Silva GM
  • Netto LE
  • Discola KF
  • Piassa-Filho GM
  • Pimenta DC
  • B├írcena JA
  • Demasi M


The FEBS journal

Publication Data

June 15, 2008

Associated Grants


Mesh Terms

  • Cloning, Molecular
  • Cysteine
  • Cytosol
  • Gene Expression Regulation, Fungal
  • Glutaredoxins
  • Glutathione
  • Hydrolysis
  • Models, Biological
  • Oxidation-Reduction
  • Proteasome Endopeptidase Complex
  • Saccharomyces cerevisiae
  • Thioredoxins