Biphasic Response of the Voltage Induced Gating of Lysenin Channels

Lysenin is a pore-forming toxin extracted from earthworms, which inserts large conducting channels in both artificial and natural lipid membranes. Unlike any other pore-forming toxin, Lysenin presents asymmetrical voltage induced gating at depolarizing membrane potentials. Lysenin behaves similar to ion channels by presenting two states, open and closed, and their occupancy is described by a Boltzmann distribution. However, our recordings at high-depolarizing potentials indicate a biphasic response to external voltages, which suggests significant dynamic changes in the energy landscape elicited by channel gating. We associated this unusual response to a potential electromechanical coupling between the voltage domain sensor and the lipid membrane. Such behavior may explain the bistability of ion channels and endow them with memory capabilities.