Structure and fungicidal activity of a synthetic antimicrobial peptide, P18, and its truncated peptides.

P18 (KWKLFKKIPKFLHLAKKF-NH2) is an antimicrobial peptide designed from a cecropin A-magainin 2 hybrid that has potent antibacterial activity without hemolytic activity against human erythrocytes. In this study, P18 displayed potent fungicidal activity (MIC: 12.5 approximately 25 microM) against pathogenic fungi, Candida albicans, Trichosporon beigelii, Aspergillus flavus and Fusarium oxyspovrum. The central Pro9 residue and the entire sequence of P18 are essential for its full fungicidal activity. Circular dichroism analysis suggested that the higher alpha-helical content of the peptides did not correlate with the stronger fungicidal activity.