Effect of Dipole Potential of Lipid Bilayers on Properties of Ion Channels Formed by Cyclic Lipodepsipeptide Syringomycin E

Effect of membrane dipole potential (phi(d)) on properties of the ion channels formed in bilayer lipid membranes (BLM) by syringomycin E (SRE), a toxin produced by Pseudomonas syringae, has been studied. It was found that phi(d) affected the conductance and life time of elementary SIZE channels as well as their cluster organization, in particular, the number of elementary channels synchronously opened in the cluster and the cluster life time. The channel-forming activity of SRE was found to be phi(d)-dependent. Analysis of experimental data revealed that (i) the mechanisms of the observed effects involve the dipole-dipole and charge-dipole interactions responsible for the cooperative functioning of the elementary SRE channels; (ii) about 95% of membrane dipole potential is shielded in the SRE pore; (iii) the channel-forming activity of SRE is mainly determined by the gating charge of the SRE channels. At the same time, partition coefficient between the membrane and aqueous phase as well as the chemical component of the channel formation work is responsible also for the phi(d) dependence of the SIZE channel forming activity.