将大肠杆菌OmpA信号肽改造成为抗菌肽的研究

Study on conversion of Omp A signal peptide of Escherichia coli to antimicrobial peptide

目的探讨将大肠杆菌OmpA信号肽改造成抗菌肽的方法以及衍生肽的杀菌活性。方法以由21个氨基酸残基组成的大肠杆菌OmpA信号肽(P-AQA)为模板,通过改变其C末端的氨基酸组成,分别合成衍生多肽:(MKKTAIAIAVALAGFARVRQK,P-RQK)、(MKKTAIAIAVALAGFARRKKK,P-KKK)、(MKKTAIAIAVALAGFAD VDQD,P-DQD)。采用琼脂铺板计数法测定以上3条衍生多肽及肠杆菌OmpA信号肽对革兰阳性菌(G^+)(金黄色葡萄球菌)和革兰阴性菌(G-)(大肠杆菌)的杀菌活性。结果天然信号肽P-AQA不溶解水,无杀菌活性;在信号肽C末端加入酸性氨基酸的衍生肽P-DQD对G^+菌和G-菌均无杀菌作用;其余两条在末端加入碱性氨基酸的多肽对G^+菌和G-菌均有较强的杀菌作用,其中末端带有5个碱性氨基酸的多肽(P-KKK)其杀菌活性强于有3个碱性氨基酸的多肽(P-RQK)5倍。结论将大肠杆菌Omp A信号肽C末端中的中性氨基酸替换为碱性氨基酸后,具有明显的杀菌活性,其杀菌活性可能与碱性氨基酸的数量有关。

Objective To study the method of conversing the OmpA signal peptide of E. coli into antimicrobial peptide and its bactericidal activity. Methods The OmpA signal peptide （P-AQA） of E. Coli that consists of 21 amino acids was used as template, three derived peptides（MKKTAIAIAVALAGFARVRQK,P-RQK）、（MKKTAIAIAVALAGFARRKKK,P-KKK）、（MKKTAIAIAVALAGFAD VDQD,P-DQD）were synthesized by changing the amino acid composition of the Cterminal of the OmpA signal peptide of E. coli. The bactericidal activity of the three derived peptides against grampositive bacteria （G＋） （Staphylococcus aureus） and gramnegative bacteria （G-） （Escherichia coli） was determined by agar plate counting method. Results The natural signal peptide PAQA was insoluble in water, the bactericidal activity could not determine; the peptide PDQD with acidic amino acid added at the Cterminal of the signal peptide had no bactericidal action on G＋ and G-; the other two polypeptides with the basic amino acid at the terminal had strong bactericidal action to G＋ and G- , and the bactericidal activity of the polypeptides with 5 basic amino acids at the terminal was about 5 times higher than that of 3 basic amino acids. Conclusions The derived peptide which neutral amino acid was replaced by basic amino acids in the Cterminal of the OmpA signal peptide of E. coli, with evident bactericidal activity, and the bactericidal activity might be correlated with the numbers of basic amino acids.