Cecropin A - magainin 2 hybrid peptides having potent antimicrobial activity with low hemolytic effect

In order to obtain peptides having improved antimicrobial activity with low hemolytic effect, a hybrid peptide (CA-MA) composed from cecropin A (1-8) and magainin 2(1-12), and its analogues with amino acid substitutions were designed and synthesized. The antimicrobial activities against bacterial cells and hemolytic activities against human red blood cells were analyzed for each peptide. Secondary structures of the peptides in aqueous solution, 50% trifluoroethanol, and sodium dodecylsulfate micelles were estimated using circular dichroism spectroscopy. The increase in hydrophobicity or alpha-helicity of the peptides correlated with an increase in hemolytic activity rather than antimicrobial activity. The substitution of Leu for Ser at position 16 in CA-MA resulted in a remarkable increase in antimicrobial activity without a significant change in hemolytic activity. Furthermore, the increase in antimicrobial activity of the peptides was not always accompanied by the increase in hemolytic activity.