Phospholipid-dependent changes in membrane permeability induced by staphylococcal δ-lysin and bee venom melittin

Abstract

The effect of purified staphylococcal δ-lysin and bee venom melittin on the permeability of large unilamellar vesicles (liposomes) composed of structurally defined lipids was investigated by following release of sequestered ATP using a bioluminescent assay. ATP release was linearly related to the logarithm of the peptide concentration. Sensitivity to the lytic peptides, as measured by the release of ATP and the slope of the dose–response curve, depended on the chain length and the degree of saturation of the hydrocarbon substituents of the phospholipid in the vesicles. Neither the sign of the surface charge nor the presence of sterol had any significant effect on the sensitivity of liposomes to peptide-induced lysis. Release of ATP and haemoglobin from intact sheep and cod erythrocytes was also determined after their exposure to δ-lysin and melittin. Both cell types showed similar degrees of sensitivity to each lytic peptide when ATP release was followed, but the release of haemoglobin from sheep erythrocytes by δ-lysin was much less than from cod erythrocytes. The implications of these results on the mode of action of the two agents are discussed.