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

A 25-mer cationic peptide pleurocidin, isolated from the winter flounder, h as broad antibacterial activity. To clarify the structure-activity relation ship, its properties and biological activity were examined. CD measurements showed that pleurocidin took an a-helical structure in the presence of DOP C/DOPG (3.1, anionic) vesicles. Very weak hemolytic activity of pleurocidin was observed and its antibacterial activity was moderate. Tryptophan fluor escence shift measurements showed that pleurocidin interacted weakly with a neutral phospholipid, but strongly with an acidic phospholipid. The peptid e exhibited weak dye-leakage activity for DOPC (neutral) vesicles and moder ate activity for acidic vesicles. From experiments on dye-leakage activity and membrane translocation of the peptide, it seemed likely that pleurocidi n, like magainin 2, forms pores in the lipid membrane. A study of amino aci d substitution in pleurocidin revealed that sc-helicity, rather than hydrop hobicity, affects the properties and activity of the peptide.