Antibacterial Activity of Arg/Pro-Rich Bactenecin 5 Model Peptides and Their Interaction with Phospholipid Membranes

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Abstract
H-Arg-Phe-Arg-Pro-Pro-Ile-Arg-(Arg-Pro-Pro-Phe)n-NH2 (n = 2—5 and 7), models of antibacterial bactenecin 5, were synthesized. The CD measurement showed that they took polyproline II-like conformations in neutral lipid vesicles at 25 and 50 °C, and in acidic ones at 25 °C. However, their conformations changed in acidic lipid vesicles at 50 °C. The membrane perturbation activity of the peptides was also found only for acidic lipid vesicles at 50 °C. The perturbation activity increased with increasing in the peptide chain length. All peptides exhibited negligible hemolytic activity for rabbit erythocytes, whereas they, except for the shortest peptide, had moderate or strong antibacterial activity against Gram-positive and Gram-negative bacteria. Together with the previous results, the N-terminal cationic portion and a certain peptide chain length were found to be important for antibacterial activity.