Ion Selectivity of Lysenin Channels

Ion channels in living systems show a pronounced selectivity for transported ions. This key feature is used by living cells to create and maintain electrochemical gradients that participate in multiple physiological functions. Our work focuses on measuring permeability of lysenin channels from anions and cations. Our experiments are comprised of an electrophysiology setup that includes lysenin channels inserted into planar bilayer lipid membranes. The solutions bathing the membrane are wired to an Axopatch 200B electrophysiology amplifier through Ag/AgCl electrodes. The transmembrane voltages, measured for asymmetrical ionic conditions, have been estimated from the intercept of I-V plots. The experimental values of the transmembrane voltages have been fitted with the Goldman-Hodgkin-Katz equation and indicated that lysenin channels discriminate between anions and cations. Our research showed that owing to the ionic selectivity, it is possible to produce transmembrane voltages in the physiological range (up to +/-100mV). Measurements of the transmembrane voltages at different ionic compositions suggest that lysenin channels also possess supplementary selectivity for cations only.