Intracellular Mn (II)-associated superoxide scavenging activity protects Cu,Zn superoxide dismutase-deficient Saccharomyces cerevisiae against dioxygen stress.
Three Cu,Zn superoxide dismutase (SOD-1)-deficient Saccharomyces cerevisiae mutants do not grow in 100% O2 in rich medium and require Met and Lys when grown in air (Bilinski, T., Krawiec, Z., Liczmanski, A., and Litwinska, J. (1985) Biochem. Biophys. Res. Commun. 130, 533-539). We show herein that medium manganese (II) accumulated by the mutants rescues these O2-sensitive phenotypes; 2 mM medium Mn2+ represented the threshold required for cell growth. The accumulation of Mn2+ was not oxygen-inducible since mutants grown aerobically and anaerobically accumulated the same amount of Mn2+. Mn2+ accumulation is not unique to these mutants since wild type accumulated almost twice as much Mn2+ as did mutant. ESR spectra of the cell extracts and whole cells loaded with Mn2+ were typical of free Mn(II) ion. These spectra could not account quantitatively for the total cellular Mn2+, however. A screen for soluble antioxidant activities in the Mn2+-supplemented cells detected O2- (superoxide) scavenging activity, with no change in catalase or peroxidase activities. This O2- scavenging activity was CN- and heat-resistant. No achromatic bands were revealed in nondenaturing gels of Mn2+- containing cell extracts stained for O2- scavenging activity. The Mn2+-dependent O2- scavenging activity in the cell extracts was quenched by EDTA and dialyzable. More than 60% of both the intracellular Mn2+ and the O2- scavenging activity was removed by 2-h dialysis. Dialyzed cells were not viable in air unless resupplemented with either Met or Mn2+. Although Mn2+ supported the aerobic growth of these mutants, excess Mn2+, which correlated with an elevated O2- scavenging activity, was toxic to both mutant and wild type. The results indicate that free or loosely bound Mn2+ ion protects the mutants against oxygen stress by providing an intracellular, presumably cytosolic, O2- scavenging activity which replaces the absent SOD-1.
Chang
E C
EC
Department of Biochemistry, School of Medicine and Biomedical Sciences, State University of New York, Buffalo 14214.
Kosman
D J
DJ
D000483:Alleles; D004578:Electron Spin Resonance Spectroscopy; D005838:Genotype; D007700:Kinetics; D008345:Manganese / Q000378:metabolism* / Q000494:pharmacology; D009154:Mutation; D010100:Oxygen / Q000494:pharmacology*; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000235:genetics / Q000254:growth & development*; D013482:Superoxide Dismutase / Q000235:genetics*; D013481:Superoxides / Q000378:metabolism*
D013481:Superoxides; D008345:Manganese; D013482:Superoxide Dismutase; D010100:Oxygen