<scp>NMR</scp> structural studies of antimicrobial peptide, <scp>LPcin</scp>‐<scp>YK5</scp>, with divalent metal ion and its antimicrobial activity

Abstract Research studies on antimicrobial peptides (AMPs) that can combat antibiotic‐resistant bacteria, an issue with antibiotic usage, are garnering attention. Among the AMP types, cationic AMPs can electrostatically interact with the bacterial membrane and destroy it, resulting in bacterial death. In the presence of metal ions, these cationic AMPs possess beneficial antimicrobial activity. In the present study, through structural change analysis and antimicrobial activity tests, we elucidated whether LPcin‐YK5, a bovine‐derived AMP analog with enhanced antimicrobial activity, interacts with the divalent ions copper(II) and zinc(II) ions. We observed that the interaction between YK5 and divalent ions contributed to the secondary structure stability of YK5, resulting in a synergistic effect on the antimicrobial activity; this is consistent with the interaction between other cationic AMPs and divalent ions. Interestingly, the secondary structural changes and antimicrobial activity against gram‐negative bacteria of YK5 were more notable in the presence of zinc(II) than in that of copper(II). Therefore, the effects of YK5 and divalent ions may have implications for designing antibiotics against antibiotic‐resistant microorganisms.