A short alpha-helical antimicrobial peptide with antibacterial selectivity.

A 13-residue alpha-helical peptide (K6L5WP), designed from Leu6-->Pro substitution of a hemolytic alpha-helical peptide (K6L6W), exhibited strong antibacterial activity (MIC: 2 to approximately 4 microM against three gram-positives and three gram-negatives) comparable to that of melittin but had no hemolytic activity. Tryptophan fluorescence studies indicated bacterial selectivity of K6L5WP is closely related to the selective interaction with negatively charged phospholipids on the surface of bacterial cells. These results suggested that the central Pro6 in K6L5WP plays an important role in its bacterial cell selectivity. In conclusion, K6L5WP with antibacterial selectivity may serve as an attractive candidate for the development of antimicrobial agents.