Overexpression and simple purification of human superoxide dismutase (SOD1) in yeast and its resistance to oxidative stress.
The structural gene of human Cu/Zn superoxide dismutase (hSOD1) was cloned into a yeast expression vector containing the promoter of the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene. The recombinant plasmid produced hSOD1 (20 kDa), about 6% of the total cellular protein, and the expressed hSOD1 was enzymatically active. The hSOD1 was purified from the cultured yeast by ammonium sulfate-methanol extraction and DEAE-cellulose column chromatography. This relatively simple purification method produced a single band on analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The amount of hSOD1 appeared to be considerably increased in cultures of higher cell density. The yeast overexpressing hSOD1 appeared to be more resistant to oxidative stresses such as paraquat, menadione and heat shock.