Properties of Voltage-gated Ion Channels Formed by Syringomycin E in Planar Lipid Bilayers

Abstract

Using the planar lipid bilayer technique we demonstrate that the lipodepsipeptide antibiotic, syringomycin E, forms voltage-sensitive ion channels of weak anion selectivity. The formation of channels in bilayers made from dioleoylglycerophosphatidylserine doped with syringomycin E at one side (1-40 micrograms/ml) was greatly affected by cis-positive voltage. A change of voltage from a positive to a negative value resulted in (i) an abrupt increase in the single channel conductance (the rate of increase was voltage dependent) simultaneous with (ii) a closing of these channels and an exponential decrease in macroscopic conductance over time. The strong voltage dependence of multichannel steady state conductance, the single channel conductance, the rate of opening of channels at positive voltages and closing them at negative voltages, as well as the observed abrupt increase of single channel conductance after voltage sign reversal suggest that the change of the transmembrane field induces a significant rearrangement of syringomycin E channels, including a change in the spacing of charged groups that function as voltage sensors. The conductance induced by syringomycin E increased with the sixth power of syringomycin E concentration suggesting that at least six monomers are required for channel formation.

Mannosyl-Diinositolphospho-Ceramide, the Major Yeast Plasma Membrane Sphingolipid, Governs Toxicity of Kluyveromyces lactis Zymocin

“…Based on heat shock sensitivity and nystatin resistance, phenotypes shared by kti6 and kti10 plasma membrane H ϩ -ATPase mutants (50), KTI6 is possibly involved in membrane function. In support of this idea, resistance to zymocin and antifungals (hygromycin B, syringomycin E, and defensin DmAMP1) that require and alter membrane function and permeability suggests that kti6 cells deny the docking or uptake of antimycotics (15,58,60). This reinforces a plasma membrane role of KTI6 and its function for antizymosis.…”

Syringomycin E Inhibition of Saccharomyces cerevisiae : Requirement for Biosynthesis of Sphingolipids with Very-Long-Chain Fatty Acids and Mannose- and Phosphoinositol-Containing Head Groups

“…One possibility is that the structural modifications that they impart are necessary for proper binding of syringomycin E to the plasma membrane that leads to channel formation (14). M(IP) 2 C and MIPC (produced by Syr4p/ Ipt1p and by Csg1p/Sur1p and Csg2p, respectively) are abundant in the plasma membrane (24) and will significantly increase the negative charge density on the outer surface of this membrane.…”

“…syringae strains (5). Syringomycin E interacts with the fungal plasma membrane, where it causes K ϩ efflux, Ca 2ϩ influx, and changes in membrane potential by processes that are likely related to channel formation (14,38).…”

Channel-forming activity of syringopeptin 25A in mercury-supported phospholipid monolayers and negatively charged bilayers

“…Since the small fluctuations were found to be exactly one fourth of the large ones, Dalla Serra et al [13] assumed that the large channels result from the tetrameric aggregation of the small channels, leading to their synchronous opening and closing, in analogy with the hexameric clusters proposed for syringomycin E [42]. In view of above results, we tentatively assumed that the first stage is mainly determined by ion flow along the large channels, which prevail over the small ones thanks to their higher level of conductance and much longer open state lifetime [15].…”