Interaction of the pore forming-peptide antibiotics Pep 5, nisin and subtilin with non-energized liposomes.

The cationic peptide antibiotics Pep 5, nisin and subtilin depolarize bacterial and artificial membranes by formation of voltage-dependent multi-state pores. Studies with non-energized liposomes indicated that the peptides do not span the membrane in the absence of a membrane potential. The effects of Pep 5 and nisin on neutral membranes, as studied by membrane fluidity, phase transition points and carboxyfluorescein efflux, were small compared to melittin. Acidic liposomes were affected more strongly, indicative of primarily electrostatic interactions with phospholipid head groups. Subtilin may slightly enter the hydrophobic core as suggested by tryptophan fluorescence quenching and liposome fusion experiments.