Voltage-dependent depolarization of bacterial membranes and artificial lipid bilayers by the peptide antibiotic nisin.
The peptide antibiotic nisin is shown to disrupt valinomycin-induced potassium diffusion potentials imposed on intact cells of Staphylococcus cohnii 22. Membrane depolarization occurred rapidly at high diffusion potentials while at low potentials nisin-induced depolarization was slower suggesting that nisin requires a membrane potential for activity. This assumption was proven in experiments with planar lipid bilayers (black lipid membranes). Macroscopic conductivity measurements indicated a voltage-dependent action of nisin. The potential must have a trans-negative orientation with respect to the addition of nisin (added to the cis-side) and a sufficient magnitude (ca.-100 mV). With intact cells the threshold potential was lower (-50 to -80 mV at pH 7.5 and below -50 mV at pH 5.5). Single channel recordings resolved transient multi-state pores, strongly resembling those introduced by melittin into artificial bilayers. The pores had diameters in the range of 0.2-1 nm, and lifetimes of few to several hundred milliseconds. The results indicate that nisin has to be regarded as a membrane-depolarizing agent which acts in a voltage-dependent fashion.
Institut für Med. Mikrobiologie und Immunologie, Universität Bonn, Federal Republic of Germany.
H G
HG
Sahl
M
M
Kordel
R
R
Benz
D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008051:Lipid Bilayers / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects; D009561:Nisin / Q000494:pharmacology*; D011188:Potassium / Q000378:metabolism; D013210:Staphylococcus / Q000187:drug effects* / Q000378:metabolism
D008051:Lipid Bilayers; D009561:Nisin; D011188:Potassium