Iturin lipopeptides: interactions of mycosubtilin with lipids in planar membranes and mixed monolayers

The interactions between the antifungal lipopeptide mycosubtilin and lipids are studied. Mycosubtilin increases the ion permeability of planar lipid membranes by forming ion conducting pores. The lifetime of these pores is greatly increased when the membrane contains cholesterol. In mixed monolayers the interaction between mycosubtilin and DMPC leads to the formation of a mycosubtilin/DMPC 1:2 complex non miscible in the excess DMPC monolayer but miscible in the mycosubtilin monolayer. Mycosubtilin and cholesterol interact strongly in monolayers in all proportions and form a mycosubtilin-cholesterol (1:2) complex. These results are analyzed with reference to the overall view of the activity of iturins and the importance of the lipopeptide conformation is outlined.