Effects of Substituting Arginine by Lysine in Bovine Lactoferricin Derived Peptides: Pursuing Production Lower Costs, Lower Hemolysis, and Sustained Antimicrobial Activity

Monomeric, dimeric, palindromic, and tetrameric peptides derived from bovine lactoferricin (LfcinB) containing the RRWQWR or the KKWQWK sequence were synthesized via SPPS- Fmoc/tBu strategy, and Lys-peptides showed higher synthesis efficiency. The antibacterial activity of the peptides against Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus ATCC reference strains and a multidrug resistant clinical isolate was evaluated. Lys peptides exhibited similar antibacterial activity to the Arg peptides, suggesting that the Arg for Lys substitution does not significantly affect the antibacterial activity. The synergy assays showed that the covalent dimeric Lys peptide decreased the MIC value of the ciprofloxacin up to 32 times, and LfcinB (20-25), and one of the Lys-peptides [K]-LfcinB (20-25)_Pal presented a synergistic effect. Additionally, Lys peptides lowered the hemolytic activity by 2 to 7 times. These results suggest that short peptides derived from Lys-LfcinB could be a cost-effective alternative for the development of drugs or combinatory treatments against bacterial infections.