Mitochondrial Protein Oxidation in Yeast Mutants Lacking Manganese-(MnSOD) or Copper- and Zinc-containing Superoxide Dismutase (CuZnSOD)

Abstract

Saccharomyces cerevisiae expresses two forms of superoxide dismutase (SOD): MnSOD, encoded by SOD2, which is located within the mitochondrial matrix, and CuZnSOD, encoded by SOD1, which is located in both the cytosol and the mitochondrial intermembrane space. Because two different SOD enzymes are located in the mitochondrion, we examined the relative roles of each in protecting mitochondria against oxidative stress. Using protein carbonylation as a measure of oxidative stress, we have found no correlation between overall levels of respiration and the level of oxidative mitochondrial protein damage in either wild type or sod mutant strains. Moreover, mitochondrial protein carbonylation levels in sod1, sod2, and sod1sod2 mutants are not elevated in cells harvested from mid-logarithmic and early stationary phases, suggesting that neither Mn-SOD nor CuZnSOD is required for protecting the majority of mitochondrial proteins from oxidative damage during these early phases of growth. During late stationary phase, mitochondrial protein carbonylation increases in all strains, particularly in sod1 and sod1sod2 mutants. By using matrix-assisted laser desorption ionization time-of-flight mass spectrometry, we have found that specific proteins become carbonylated in sod1 and sod2 mutants. We identified six mitochondrial protein spots representing five unique proteins that become carbonylated in a sod1 mutant and 19 mitochondrial protein spots representing 11 unique proteins that become carbonylated in a sod2 mutant. Although some of the same proteins are carbonylated in both mutants, other proteins are not. These findings indicate that Mn-SOD and CuZnSOD have both unique and overlapping functions in the mitochondrion.

Robustness ofSaccharomyces CerevisiaeGenome to Antioxidative Stress

“…This supports the assumption that alternative pathways exist for detoxification of superoxide radicals in these organelles such as functioning of metallothioneins, yeast small cysteine-rich proteins with antioxidant properties (24). However, the same authors (35) showed that MnSOD and CuZnSOD in some instances have both unique and overlapping functions in protecting the mitochondria from oxidative damages. Other detoxification enzymes that play an important role in drug resistance in all eukaryotic species are the glutathione S-transferases (GSTs).…”

“…In addition, mutations in SSQ1, JAC1, NFS11 and ISU1 suppress the auxotrophies caused by a sod1 mutations, but do not reverse the sensitivity of sod1 strains to paraquat (25). As regards the sod2 mutants, recent investigations of O'Brien et al (35) indicated that in mid-logarithmic and early stationary phase neither CuZnSOD nor MnSOD are required for protecting the majority of mitochondrial proteins from oxidation. Carbonylation only increases in these mutants during the stationary phase.…”

Yeast Colony Survival Depends on Metabolic Adaptation and Cell Differentiation Rather Than on Stress Defense

“…This could result in a drop of ammonia production and insufficient activation of important metabolic changes. Some highly carbonylated mitochondrial proteins were observed in the sod2⌬ mutant (26).…”

The Potato Tuber Mitochondrial Proteome

“…5). Also, we identified both the classical mitochondrial Mn-SOD as well as a copper/ zinc [Cu/Zn]-SOD, which at least in yeast is found in the mitochondrial intermembrane space (O'Brien et al, 2004). Mn-and Cu/Zn-SODs showed high (21.7 [log 10 (dNSAF)]) and medium (23.5 [log 10 (dNSAF)]) relative abundances, respectively.…”