家蝇防御素抗菌肽Des-hf突变体的抑菌活性研究

采用PCR定点诱变技术，将家蝇防御素抗菌肽成熟肽段的基因（des-hf gene）倒数第九个氨基酸由甘氨酸（G）突变为带正电荷的精氨酸（R），构成第一个突变体des-hf-MU1。采用同样的方法在des-hf 基因的C端加上六个带有正电荷的赖氨酸（K），构成第二个突变体des-hf-MU2。采用毕赤酵母表达系统对上述两个突变体进行表达，抗菌特性表明表达产物对金黄色葡萄球菌有较好的抑菌活性，根据琼脂孔扩散法检测des-hf-MU1和des-hf-MU2的抑菌效价比des-hf分别提高了2.4倍和8.0倍，且在PH值为5～6时活性最高，热稳定性实验显示des-hf-MU1、des-hf-MU2 100 ℃加热10min 后仍具有抑菌活性，这些充分显示了良好的应用前景。

Study on the Antibacterial Activity of Two Musca domestica Defensin Mutants

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.