Rational Design of a MAP 34‐B‐Derived Peptide Confers Potent Membrane‐Targeting Activity against Escherichia coli and

ABSTRACT

The global spread of antimicrobial resistance, particularly among clinically important Gram‐negative pathogens, has intensified the search for effectives to conventional antibiotics. Antimicrobial peptides are promising, as they act rapidly on bacterial envelopes and may circumvent resistance. Here, we rationally designed two derivatives of MAP 34‐B, MAP 34B‐1, and MAP 34B‐2 and comparatively evaluated their antibacterial activity, physicochemical stability, membrane‐associated mechanism, and cytocompatibility. MAP 34B‐1 displayed stronger and broader activity against Escherichia coli and Acinetobacter baumannii than MAP 34B‐2 and rapidly reduced bacterial viability within 2 h. In contrast, MAP 34B‐2 exhibited a narrower antibacterial spectrum and weaker activity against A. baumannii . Scanning electron microscopy revealed morphological damage of bacterial cells, FITC‐labeled peptide localization confirmed membrane binding, and membrane permeability assays demonstrated disruption of membrane integrity. Collectively, these results support a membrane‐associated antibacterial mechanism for MAP 34B‐1. Both derivatives retained antibacterial activity under the tested salt and thermal conditions. Notably, MAP 34B‐1 caused less mammalian‐cell cytotoxicity and hemolysis than MAP 34B‐2, resulting in a more favorable balance between antibacterial potency and host‐cell compatibility. Overall, these findings demonstrate that rational sequence optimization of MAP 34‐B can substantially modulate antibacterial spectrum, membrane activity, and biocompatibility. MAP 34B‐1 therefore represents a promising lead peptide for further development against infections caused by E. coli and A. baumannii .