INTERACTION OF MASTOPARAN-B AND ITS ALA-SUBSTITUTED ANALOGS WITH PHOSPHOLIPID-BILAYERS

The interaction of mastoparan B, a tetradecapeptide toxin found in the hornet Vespa basalis, with phospholipid bilayers was investigated. Sy nthetic mastoparan B and its analogs, obtained by substituting one hyd rophilic amino acid (2-Lys, 4-Lys, 5-Ser, 8-Ser, 11-Lys, or 12-Lys) in mastoparan B with Ala, were studied. Mastoparan B and its analogs wer e synthesized by the solid-phase method. As shown by circular dichrois m spectra, mastoparan B and its analogs adopted an unordered structure in buffer solution. All peptides took an a-helical structure, and the a-helical content of its analogs increased in the presence of neutral and acidic liposomes as compared to that of mastoparan B. In the calc ein leakage experiment, we observed that mastoparan B interacted more weakly with lipid bilayers in neutral and acidic media than its analog s. Mastoparan B also showed slightly lower antimicrobial activity and hemolytic activity towards human erythrocytes than its analogs. These results indicate that the greater hydrophobicity of the amphiphilic a- helix of mastoparan B by replacement with alamine residues results in the increased biological activity and helical content.