Temporin A (TA) is a small, basic, highly hydrophobic, antimicrobial peptide amide (FLPLIGRVLSGIL-NH2) found in the skin of the European red frog, Rana temporaria. It has variable antibiotic activities against a broad spectrum of microorganisms, including clinically important methicillin-sensitive and -resistant Staphylococcus aureus as well as vancomycin-resistant Enterococcus faecium strains. In this investigation the antimicrobial activity and structural characteristics of TA synthetic analogs were studied. For antibacterial activity against S. aureus and enterococcal strains, the hydrophobicity of the N-terminal amino acid of TA was found to be important as well as a positive charge at amino acid position 7, and bulky hydrophobic side chains at positions 5 and 12. Replacing isoleucine with leucine at amino acid positions 5 and 12 resulted in the greatest enhancement of antibacterial activity. In addition, there was little difference between the activities of TA and its all-D enantiomer, indicating that the peptide probably exerts its effect on bacteria via non-chiral interactions with membrane lipids.
