Interaction of grammistins with lipids and their antibacterial activity

Grammistins are hemolytic and ichthyotoxic peptides in the skin secretion o f soap-fishes and are structurally characterized by their abundance in amph iphilic a-helicity. In the present study, their interaction with lipids and lipid vesicles as well as antibacterial activity were examined using four grammistins (Gs 1 and Gs 2 from Grammistes sexlineatus and Pp 1 and Pp 3 fr om Pogonoperca punctata). The hemolytic activity of grammistins was inhibit ed by phospholipids but not by cholesterol. Moreover, grammistins released carboxyfluorescein entrapped within liposomes made of phosphatidylcholine. In contrast, grammistins were found to have antibacterial activity with a b road spectrum against nine species of bacteria, including both Gram-negativ e and Gram-positive groups. The potency of their antibacterial activity was not related to that of hemolytic activity, suggesting that grammistins bin d to membrane phospholipids but lyse erythrocyte and bacterial membranes vi a different mechanisms. Conclusively, grammistins are new members of the fa mily of cell non-selective membrane-lytic peptides with amphiphilic a-helic es, being similar to pardaxins, which are secreted from the skin of soles, and to melittin, which is derived from bee venom.