Faculty Mentor Information
Dr. Daniel Fologea (Mentor), Boise State University
Additional Funding Sources
This research was supported by the National Science Foundation CAREER grant #1554166, the Idaho State Board of Education grant #3941020, the TRIO UPWARD BOUND, and the Department of Physics at Boise State University.
Abstract
Lysenin, a pore-forming toxin extracted from the red earthworm E. fetida, inserts large conductance channels in artificial and natural lipid membranes containing sphingomyelin. Based on prior reports showing that lysenin channels interact with many multivalent metals by employing a ligand-gated mechanism, we hypothesized that lysenin channels might similarly interact with Sn2+ ions in water-aqueous solutions. Our investigations were conducted on lysenin channels reconstituted in planar bilayer lipid membranes composed of Asolectin, Sphingomyelin, and Cholesterol and bathed by buffered electrolyte solutions. The electrical measurements were performed with an Axopatch 200B electrophysiology amplifier in a voltage clamp setting. The conductance of the channel-containing membranes was assessed from IV plots recorded in response to ramp voltages. Our results show that Sn2+ addition diminishes the membrane’s conductance in a concentration-dependent and cooperative manner. Single channel measurements allowed the identification of a ligand-gated mechanism responsible for the reduced conductance. Additionally, precipitation of Sn2+ ions by phosphate addition restored the original conductance, suggesting a reversible gating mechanism. These results are anticipated to contribute to a better understanding of the physiological role of lysenin channels and lead to applications that rely on the controlled passage of ions and molecules through natural and artificial lipid membranes.
Interactions of Lysenin Channels with Sn2+ Ions
Lysenin, a pore-forming toxin extracted from the red earthworm E. fetida, inserts large conductance channels in artificial and natural lipid membranes containing sphingomyelin. Based on prior reports showing that lysenin channels interact with many multivalent metals by employing a ligand-gated mechanism, we hypothesized that lysenin channels might similarly interact with Sn2+ ions in water-aqueous solutions. Our investigations were conducted on lysenin channels reconstituted in planar bilayer lipid membranes composed of Asolectin, Sphingomyelin, and Cholesterol and bathed by buffered electrolyte solutions. The electrical measurements were performed with an Axopatch 200B electrophysiology amplifier in a voltage clamp setting. The conductance of the channel-containing membranes was assessed from IV plots recorded in response to ramp voltages. Our results show that Sn2+ addition diminishes the membrane’s conductance in a concentration-dependent and cooperative manner. Single channel measurements allowed the identification of a ligand-gated mechanism responsible for the reduced conductance. Additionally, precipitation of Sn2+ ions by phosphate addition restored the original conductance, suggesting a reversible gating mechanism. These results are anticipated to contribute to a better understanding of the physiological role of lysenin channels and lead to applications that rely on the controlled passage of ions and molecules through natural and artificial lipid membranes.