Interaction of pleurocidin and its analogs with phospholipid membrane and their antibacterial activity

: A 25-mer cationic peptide pleurocidin, isolated from the winter flounder, has broad antibacterial activity. To clarify the structure–activity relationship, its properties and biological activity were examined. CD measurements showed that pleurocidin took an α-helical structure in the presence of DOPC/DOPG (3 : 1, anionic) vesicles. Very weak hemolytic activity of pleurocidin was observed and its antibacterial activity was moderate. Tryptophan fluorescence shift measurements showed that pleurocidin interacted weakly with a neutral phospholipid, but strongly with an acidic phospholipid. The peptide exhibited weak dye-leakage activity for DOPC (neutral) vesicles and moderate activity for acidic vesicles. From experiments on dye-leakage activity and membrane translocation of the peptide, it seemed likely that pleurocidin, like magainin 2, forms pores in the lipid membrane. A study of amino acid substitution in pleurocidin revealed that α-helicity, rather than hydrophobicity, affects the properties and activity of the peptide.