Bactericidal efficiency and mechanism of specifically targeted antimicrobial peptides optimized based on structural and functional relationships

In contrast to traditional broad-spectrum antibiotics, it is difficult for bacteria to develop resistance to most specifically targeted antimicrobial peptides (STAMPs), moreover, they can maintain a normal ecological balance and provide long-term protection for the body. However, therapeutic applications of STAMPS are hindered by their weak activity, and imperfect specificity as well as lack of knowledge to understand their structure-activity relationships. To further investigate the effects of different parameters on the biological activities of STAMPs, a peptide sequence, WKKIWKDPGIKKWIK, was truncated, extended, and provided with an increased charge and altered amphipathicity. In addition, a novel template modification method was introduced, in which a phage-displayed peptide that recognized and bound to E. coli cells was attached at the end of the sequence. Compared with the traditional template modification method, peptide 11, which contained a phage-displayed peptide at the C-terminus, exhibited superior narrow-spectrum antibacterial activity against E. coli compared to that of parental peptide 2, and the activity and specificity of 11 were increased by 5.0 and 2.4 times, respectively. Additionally, 11 showed low cell toxicity and relatively desirable salt, serum, acid and alkaline stability. In this study, 11 specifically killed E. coli by causing cytoplasmic membrane rupture and cytosol leakage. In summary, these findings are useful for improving the activity and specificity of STAMPs and show that peptide 11 is better able to combat the growing threat of E. coli infections.