A novel antimicrobial peptide, designated macropin (MAC-1) with sequence Gly-Phe-Gly-Met-Ala-Leu-Lys-Leu-Leu-Lys-Lys-Val-Leu-NH2, was isolated from the venom of the solitary bee Macropis fulvipes. MAC-1 exhibited antimicrobial activity against both Gram-positive and Gram-negative bacteria, antifungal activity, and moderate hemolytic activity against human red blood cells. A series of macropin analogs were prepared to further evaluate the effect of structural alterations on antimicrobial and hemolytic activities and stability in human serum. The antimicrobial activities of several analogs against pathogenic Pseudomonas aeruginosa were significantly increased while their toxicity against human red blood cells was decreased. The activity enhancement is related to the introduction of either l- or d-lysine in selected positions. Furthermore, all-d analog and analogs with d-amino acid residues introduced at the N-terminal part of the peptide chain exhibited better serum stability than did natural macropin. Data obtained by CD spectroscopy suggest a propensity of the peptide to adopt an amphipathic α-helical secondary structure in the presence of trifluoroethanol or membrane-mimicking sodium dodecyl sulfate. In addition, the study elucidates the structure–activity relationship for the effect of d-amino acid substitutions in MAC-1 using NMR spectroscopy. Copyright © 2014 European Peptide Society and John Wiley & Sons, Ltd.
Novel peptide named macropin was isolated from the venom of wild bee Macropis fulvipes. It belongs to the category of amphipathic α-helical antimicrobial peptides as illustrated by its wheel projection. A series of macropin analogs were prepared to evaluate the effect of structural alterations on biological activity. The antimicrobial activities of several analogs against pathogenic Pseudomonas aeruginosa were increased while their toxicity against red blood cells was decreased. The structure of macropin and selected analogs was elucidated by NMR.