Additional Funding Sources
This project was supported by NSF Career Grant No. 1554166 and the Boise State University Department of Physics.
Presentation Date
7-2021
Abstract
The selectivity of ion channels is intrinsic to biological activity in any cell. However, other pore-forming proteins aside from ion channels also serve to create channels across a cell membrane. A typical example of transmembrane transporters is pore-forming toxins, which are virulence factors secreted by microorganisms and usually kill cells by inserting uncontrolled conducting pathways in target membranes, destroying the barrier function of the membrane. Therefore, we asked whether or not particular channels present ionic selectivity. To answer this question, we investigated the transport protein lysenin, a pore-forming toxin extracted from red earthworms. After self-insertion of lysenin channels into a target artificial membrane, we employed electrophysiology to determine if transmembrane voltages were produced by chemical gradients. Adjustments of KCl concentration on only one side of the membrane revealed the occurrence of transmembrane voltages, indicative of ionic selectivity. Further analysis of experimental data showed that lysenin channels have higher selectivity for anions. Although the physiological implications of the selectivity of pore-forming toxins are yet to be deciphered, this important feature of lysenin channels may be used to modulate the transmembrane voltage of cells. In practice, it could be developed into an artificial membrane systems that enable control over membrane permeability.
Lysenin Channel’s Selectivity to Monovalent Ions
The selectivity of ion channels is intrinsic to biological activity in any cell. However, other pore-forming proteins aside from ion channels also serve to create channels across a cell membrane. A typical example of transmembrane transporters is pore-forming toxins, which are virulence factors secreted by microorganisms and usually kill cells by inserting uncontrolled conducting pathways in target membranes, destroying the barrier function of the membrane. Therefore, we asked whether or not particular channels present ionic selectivity. To answer this question, we investigated the transport protein lysenin, a pore-forming toxin extracted from red earthworms. After self-insertion of lysenin channels into a target artificial membrane, we employed electrophysiology to determine if transmembrane voltages were produced by chemical gradients. Adjustments of KCl concentration on only one side of the membrane revealed the occurrence of transmembrane voltages, indicative of ionic selectivity. Further analysis of experimental data showed that lysenin channels have higher selectivity for anions. Although the physiological implications of the selectivity of pore-forming toxins are yet to be deciphered, this important feature of lysenin channels may be used to modulate the transmembrane voltage of cells. In practice, it could be developed into an artificial membrane systems that enable control over membrane permeability.