Channel-formation activity of the lantibiotic nisin on bilayer lipid membranes

We have performed electrical measurements on bilayer lipid membranes (BLMs) in the presence of nisin. The membranes were formed in 0.1 M KCI solution following the technique of Montal-Mueller as well as that of Rudin-Mueller. Nisin was dissolved in water and introduced in small amount into one side (cis-side) of the solution bathing the membrane to final concentrations of 10(-7)-10(-5) M. By applying external voltages of different polarity, membrane conductance increases were observed. In Montal-Mueller membranes, channels with elementary conductance of about 145 pS were detected both for trans-negative and trans-positive potentials (50 mV). Channels with elementary conductance around 400 pS were observed only for trans-negative potentials. The log-log plot of macroscopic conductance versus nisin concentration was linear with a slope of (1.0 +/- 0.1), showing that one nisin molecule is involved in channel formation.