Bactenecin and Its Three Improved Derivatives for Enhancement of Antibacterial Activity Against Escherichia coli

background: bactenecin is one of the smallest cationic eukaryotic antimicrobial peptides (amps) with a length of 12 residues and a beta-turn structure originated from bovine neutrophil cells. previous studies reported poor capability of this peptide against gram-negative bacteria. objectives: the present study aimed at investigating the bactenecin bactericidal activity and determining the effect of increasing the positive charge of amine and carboxyl terminus and increasing the hydrophobicity of the central part of the antimicrobial peptide. methods: similar to the native peptide, three designed variants were employed named bm1, bm2, and bm3 that had increased positive charges, hydrophobicity, and a combination of both, respectively. conditions for purifying and assaying their antibacterial activity against gram-negative bacteria were predicted and optimized by apd3 and expasy servers. the cloned and expressed peptides in pichia pastoris gs115 were partially purified by anion and cation exchange chromatography. the final purification rate of amps by hplc was reported to be 70% and peptides were further characterized by lc-mass analysis. finally, a minimum inhibitory concentration test was conducted. results: the results implied the more significant effect of positive charges on the performance of these peptides against escherichia coli.