The effect of dipole potential of lipid bilayers on the properties of ion channels formed by cyclic lipodepsipeptide syringomycin E

The effect of membrane dipole potential (? _d ) on the properties of ion channels formed in bilayer lipid membranes by syringomycin E (SRE), a toxin produced by Pseudomonas syringae, has been studied. It has been shown that ? _d affects the conductance and lifetime of elementary SRE channels as well as their cluster organization, in particular, the number of elementary channels synchronously opened in the cluster and the lifetime of these clusters. The channel-forming activity of SRE was found to be ? _d -dependent. The analysis of experimental data has 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; and (iii) the channel-forming activity of SRE is mainly determined by the gating charge of the SRE channels. At the same time, the partition coefficient for the toxin distribution between the membrane and aqueous phase as well as the chemical component of the channel formation work are also responsible for the ? _d -dependence of the SRE channel forming activity.