[Cloning and expression of human Cu/Zn superoxide dismutase gene in Lactococcus lactis]

The cDNA encoding human Cu/Zn SOD was amplified by RT-PCR using the total RNA of human liver as the template, and was cloned into an E. coli expression vector pET23b. After the DNA sequence was determined, the recombinant plasmid pET23bsod was introduced into E. coli BL21(DE3)/pLysS. SDS-PAGE analysis revealed that the recombinant E. coli expressed the predicted 19 kDa human Cu/Zn SOD, and its amount was over 50% of total proteins. The Cu/Zn SOD cDNA was then subcloned into a lactococcal expression vector pMG36e, and resulting pMG36esod was introduced into L. lactis MG1363 by electroporation. The human Cu/Zn-SOD was expressed up to 5% of the soluble proteins, and the enzymatic activity was also observed by SOD activity dying.