CONFORMATION AND BIOLOGICAL-ACTIVITY OF MASTOPARAN-B AND ITS ANALOGS .1.

The mode of action of mastoparan B, an antimicrobial cationic tetradec apeptide amide isolated from the hornet Vespa basalis, toward phosphol ipid bilayers was studied with synthetic mastoparan B and its analogs with individual Ala instead of hydrophobic amino acids (1-Ile, 3-Leu, 6-Leu, 7-Val, 9-Trp, 13-Val, 14-Leu) in mastoparan B. Mastoparan B and its analogs were synthesized by the solid-phase method. Circular dich roism spectra showed that mastoparan B and its analogs adopted an unor dered structure in buffer solution. In the presence of neutral and aci dic liposomes, most of the peptides took an alpha-helical structure. T he calcein leakage experiment indicated that mastoparan B interacted s trongly with neutral and acidic lipid bilayers than its analogs. Masto paran B also showed a more or less highly antimicrobial activity and h emolytic activity for human erythrocytes than its analogs. These resul ts indicate that the hydrophobic face in the amphipathic alpha-helix o f mastoparan B critically affect biological activity and helical conte nts.