Changes in a Protein Profile Can Account for the Altered Phenotype of the Yeast Saccharomyces cerevisiae Mutant Lacking the Copper-Zinc Superoxide Dismutase

Copper-zinc superoxide dismutase (SOD1) is an antioxidant enzyme that catalyzes the disproportionation of superoxide anion to hydrogen peroxide and molecular oxygen (dioxygen). The yeast Saccharomyces cerevisiae lacking SOD1 (Delta sod1) is hypersensitive to the superoxide anion and displays a number of oxidative stress-related alterations in its phenotype. We compared proteomes of the wild-type strain and the Delta sod1 mutant employing two-dimensional gel electrophoresis and detected eighteen spots representing differentially expressed proteins, of which fourteen were downregulated and four upregulated. Mass spectrometry-based identification enabled the division of these proteins into functional classes related to carbon metabolism, amino acid and protein biosynthesis, nucleotide biosynthesis, and metabolism, as well as antioxidant processes. Detailed analysis of the proteomic data made it possible to account for several important morphological, biochemical, and physiological changes earlier observed for the SOD1 mutation. An example may be the proposed additional explanation for methionine auxotrophy. It is concluded that protein comparative profiling of the Delta sod1 yeast may serve as an efficient tool in the elucidation of the mutation-based systemic alterations in the resultant S. cerevisiae phenotype.