Redox properties of the disulfide bond of human Cu,Zn superoxide dismutase and the effects of human glutaredoxin 1

Samantha D. Bouldin, Maxwell A. Darch, P. John Hart, Caryn E. Outten

Research output: Contribution to journalArticlepeer-review

23 Scopus citations

Abstract

The intramolecular disulfide bond in hSOD1 [human SOD1 (Cu,Zn superoxide dismutase 1)] plays a key role in maintaining the protein's stability and quaternary structure. In mutant forms of SOD1 that cause familial ALS (amyotrophic lateral sclerosis), this disulfide bond is more susceptible to chemical reduction, which may lead to destabilization of the dimer and aggregation. During hSOD1 maturation, disulfide formation is catalysed by CCS1 (copper chaperone for SOD1). Previous studies in yeast demonstrate that the yeast GSH/Grx (glutaredoxin) redox system promotes reduction of the hSOD1 disulfide in the absence of CCS1. In the present study, we probe further the interaction between hSOD1, GSH and Grxs to provide mechanistic insight into the redox kinetics and thermodynamics of the hSOD1 disulfide. We demonstrate that hGrx1 (human Grx1) uses a monothiol mechanism to reduce the hSOD1 disulfide, and the GSH/hGrx1 system reduces ALS mutant SOD1 at a faster rate than WT (wild-type) hSOD1. However, redox potential measurements demonstrate that the thermodynamic stability of the disulfide is not consistently lower in ALS mutants compared with WT hSOD1. Furthermore, the presence of metal cofactors does not influence the disulfide redox potential. Overall, these studies suggest that differences in the GSH/hGrx1 reaction rate with WT compared with ALS mutant hSOD1 and not the inherent thermodynamic stability of the hSOD1 disulfide bond may contribute to the greater pathogenicity of ALS mutant hSOD1.

Original languageEnglish (US)
Pages (from-to)59-67
Number of pages9
JournalBiochemical Journal
Volume446
Issue number1
DOIs
StatePublished - Aug 15 2012

Keywords

  • Cu,Zn superoxide dismutase (SOD)
  • Disulfide
  • Glutaredoxin
  • Monothiol
  • Redox potential
  • Yeast

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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