Interactions of antibiotics of the iturin group with human erythrocytes

Abstract The peptidolipid antibiotics, iturin A and bacillomycin L have a disrupting effect on erythrocyte membrane leading to a simultaneous release of K + ions and hemoglobin. The formation of ghosts is accompanied by a partial solubilisation of lipid components. Binding experiments with radioactive antibiotics show that about 7·10 7 molecules of iturin A and 4·10 7 molecules of bacillomycin L are bound to one erythrocyte at the concentration giving 100% hemolysis. This concentration is reduced by about 20% after treatment of erythrocytes by phospholipase A 2 . Scatchard plots show that the affinity for erythrocyte membrane is higher with bacillomycin L than with iturin A. This difference is probably correlated to the differences in their peptide moieties. The substitution of tyrosyl residue leads to a ten-fold increase of the concentrations giving 100% hemolysis, probably due to a low distribution coefficient of derivatives between the membrane and the solvent. This result and the humped Scatchard curves obtained with both antibiotics may be related to the self-association of the compounds in aqueous solutions.