Antibacterial activity of Cc-CATH3 peptide and its N-terminally truncated analogues against gram-positive adn gram-negative bacteria

Abstract

Cc-CATH3 is an avian antimicrobial peptide (AMP) with 29 amino acids in length containing a broad-spectrum antibacterial activity. It has been proved that the either N-terminal or C-terminal residues of AMPs is important for antibacterial activity; since the N- or C-termini is the active function that interact with bacterial membranes in an initial step of bactericidal mechanism. The aim of this study was to investigate the antibacterial activity of Cc-CATH3 and its N-terminal truncated analogues against gram-positive and gram-negative bacteria to observe the role of N-terminal of Cc-CATH3 on antibacterial activity. Cc-CATH3 could inhibit gram-positive bacteria S. aureus and B. subtilis and also gram-negative bacteria E. coli and S. typhimurium with the MIC values of 1, 8, 2 and 4 μM respectively. The first four-residue N-terminally truncated peptide appeared to be more active since it showed the antibacterial activity against the aforementioned bacteria with MIC values of 0.5, 1, 2 and 2 μM respectively. However, the peptides with eight- or twelve-residue truncation were inactive since no inhibition neither gram-positive nor gram-negative bacteria was observed. The data also indicated that the MBC values of Cc-CATH3 against S. aureus, B. subtilis, E. coli and S. typhimurium were 2, 8, 8 and 8 μM respectively while the MBC of the peptide with four-residue truncation were 1, 2, 8 and 8 uM respectively. The results conclude that the N-terminal residues of Cc-CATH3 are important for its antibacterial activity; since the peptide lose the function when it was N-terminally truncated only eight residues.