ABSTRACT A Mn-superoxide dismutase (SOD) gene (sod2) deletion mutant of Schizosaccharomyces pombe was constructed and its properties were compared with those of the mutant lacking the Cu,Zn-SOD gene (sod1). Activity staining of SOD showed that Sod1p is the major SOD activity in S. pombe cells. Unlike the sod1 mutant, the sod2 mutant did not show any amino acid auxotrophies. Unusual accumulation of superoxide could be detected in sod1 mutant cells with a fluorometric dye hydroethidine. Protein oxidation in normally growing cells increased in both SOD-deficient mutants, and was especially high in sod1 mutant cells. The sod1 mutant exhibited severe sensitivity to paraquat, menadione, and ethanol, while the sod2 mutant was moderately sensitive to these superoxide-generating agents. The sod1 and sod2 mutants slowly grew in media containing high concentrations of sorbitol. The sod1 mutant also exhibited a growth defect at 37°C. These results suggest that, like Sod1p, which has major defense activity, Sod2p partly plays a role in protecting S. pombe cells against multiple stresses, including oxidation and high osmolarity.
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