Design, synthesis and antibacterial activity studies of model peptides of proline/arginine-rich region in bactenecin7

Bactenecin7 (Bac7). a cationic antibacterial peptide, contains a repeating region of Xaa-Pro-Arg-Pro (Xaa = hydrophobic residue). To investigate the structure and property of a Pro/Arg-rich region, we synthesized a series of peptides, Xaa-Pro-Arg-Pro (Xaa Gly, Arg, Leu, Ile, and Phe) as models and characterized. The conformational preferences of these peptides in water and trifluoroethanol were examined by circular dichroism. The results suggest the presence of largely poly(Pro)-II helical conformation in aqueous and trifluoroethanol solutions. Their antibacterial activity against gram-negative bacteria such as Escherichia coli, Klebsiella Pneumoniae, Pseudomonas aeruginosa, and Escherichia coliHB101, and gram-positive bacteria such as Staphylococcus aureus were measured at various peptide concentrations. Two of our synthetic tetrapeptide fragments containing Gly and Arg were efficiently killed the gram-positive bacteria, Staphylococcus aureus, at the concentration level of 200 mug/mL.