Antibacterial activity of Arg/Pro-rich bactenecin 5 model peptides and their interaction with phospholipid membranes

H-Arg-Phe-Arg-Pro-Pro-Ile-Arg-(Arg-Pro-Pro-Phe)(n)-NH2 (n = 2-5 and 7), mod els of antibacterial bactenecin 5, were synthesized. The CD measurement sho wed that they took polyproline II-like conformations in neutral lipid vesic les at 25 and 50 degrees C, and in acidic ones at 25 degrees C. However, th eir conformations changed in acidic lipid vesicles at 50 degrees C. The mem brane perturbation activity of the peptides was also found only for acidic lipid vesicles at 50 degrees C. The perturbation activity increased with in creasing in the peptide chain length. All peptides exhibited negligible hem olytic activity for rabbit erythocytes, whereas they, except for the shorte st peptide, had moderate or strong antibacterial activity against Gram-posi tive 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.