Multiple Strategy Optimization of Specifically Targeted Antimicrobial Peptide Based on Structure–Activity Relationships to Enhance Bactericidal Efficiency

Unlike traditional broad-spectrum antibacterial agents, specifically targeted antimicrobial peptides (STAMPs) are difficult for bacteria to develop resistance to due to their unique membrane lytic mechanism. Additionally, STAMPs can maintain a normal ecological balance and provide long-term protection to the body. However, therapeutic applications of STAMPS are hindered by their weak activity and imperfect specificity, as well as lack of knowledge in understanding their structure–activity relationships. To 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 for attaching a phage-displayed peptide, which recognized and bound to Escherichia coli (E. coli) cells, to the end of the sequence was introduced. Compared with the traditional template modification method, peptide 13, 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 peptide 13 were increased by 5.0 and 2.4 times, respectively. Additionally, peptide 13 showed low cytotoxicity and relatively desirable salt, serum, acid, alkaline and heat stability. In this study, peptide 13 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 13 is able to combat the growing threat of E. coli infections.