Effect of the O-methylation of tyrosine on the pore-forming properties of iturins.

Abstract A comparison has been made between the pore-forming properties of the antibiotic lipopeptide iturin A and a derivative methylated on the tyrosine residue which shows a restricted biological activity. It is shown that this derivative increases the ion permeability of planar lipid membranes as does iturin A. Nevertheless, the global conductance of the doped membrane is very much lower at the same lipopeptide/phospholipid ratio and the ion selectivity is inverted ( P K /P Cl = 6 instead of 0.6 with iturin A). The characteristics of the induced conducting pores are also rather different. This suggests an important role of the d -Tyr 2 residue, present in all the compounds of the iturin family, both in the biological and in the pore-forming properties of iturin A.