鸭抗菌肽Cathelicidin的衍生物设计及抑菌机制研究

鸭抗菌肽Cathelicidin分子Cath(1-20)]富含疏水性氨基酸及正电荷,通过人工方法设计合成Cath(1-20)的截短肽衍生物,筛选新型安全Cath(1-20)衍生肽,探讨其作用机制。结果表明,与母肽Cath(1-20)相似,三种衍生肽Cath(5-20)、Cath(4-20)、Cath(3-20)均具有明显广谱抑菌活性,MIC值在1~8μmol·L~(-1)范围内,但仅Cath(5-20)溶血及细胞毒性明显降低,治疗指数达19.5,显著高于Cath(1-20)、Cath(4-20)及Cath(3-20)。Cath(1-20)及其衍生肽可破坏E.coli UB1005的内膜完整性,产生去极化作用,并存在时间和剂量依赖效应;透射电镜结果显示Cath(1-20)及Cath(5-20)可破坏细菌细胞膜。研究证实氨基端的色氨酸对鸭抗菌肽Cath(1-20)溶血及细胞毒性起关键作用,其作用靶点主要为细菌细胞膜。

Design of derivatives of duck antimicrobial peptide Cathelicidin and antibacterial mechanism

The duck antimicrobial peptide Cathelicidin Cath(1-20)] contains a series of amino acid residues with the characteristics of net positive charge and hydrophobicity.To screen novel derived peptides of Cath(1-20) with ideal activity and investigated its antibacterial mechanism,truncated peptide derivatives of Cath(1-20) were designed and synthesized by chemical method.The results showed that similar to the parent peptide Cath(1-20),its three derivatives,Cath(5-20),Cath(4-20),Cath(3-20),showed strong antimicrobial activity against a broad range of bacteria in vitro,with minimum inhibitory concentrations in the range of 1-8 μmol· L1.However,only Cath(5-20) did not show obvious hemolytic activity and cytotoxicity.The therapeutic index of Cath(5-20) was 19.5,much higher than those of Cath(1-20),Cath(4-20) and Cath(3-20).Cath(1-20) and its derivatives were able to increase inner membrane permeability and depolarize the cell membrane of E.coli UB1005 in a dose-and time-dependent manner.The result of transmission electron microscopy also showed that Cath(1-20) and Cath(5-20) could destroy bacterial cell membrane.This study demonstrated that the tryptophan at the amino terminal played crucial role in the hemolysis and cytotoxicity of duck antimicrobial peptide Cath (1-20) and its main target was bacterial cell membrane.