Abstract：Site-directed mutagenesis to replace residue 32 of Musca domestica Defensin gene (glycin, G) with arginine (cationic amino acids) by recombinant PCR, In this way, the first mutant des-hf-MU1 was gained. Six lysines (K) were added to the C terminal of des-hf gene in the same way, forming the second mutant des-hf-MU2.The two mutant were expressied in Pichia expression system, The expression product showed perfect autibacteril activity against gram-postive bacterias.According to Agarose Diffusion Assay, the anti-bacteria activity of des-hf-MU1 is 2.4 times than des-hf, and des-hf-MU2 is 8.0 times than that. Moreover, the activity is hightest when PH is 5~6, heat stability experiment showed that the antibacterial activity still exist when des-hf-MU1 and des-hf-MU2 were heated to100℃.Above all reveals sufficiently that ds-hf-MU1 and des-hf-MU2 have good perspective in application.
