Ionic Selectivity of Protein Channels in Subconducting States
Additional Funding Sources
The project described was supported by the Ronald E. McNair Post-Baccalaureate Achievement Program through the U.S. Department of Education under Award No. P217A170273. The project described was supported by the National Science Foundation under Award No. 1554166
Abstract
The directed transport of ions via ion channels embedded into cell membranes is essential for nutrition, maintaining and creating electrical gradients, communication, and information processing and transmission. A large variety of physiological functions are ensured by channels that present selectivity for ionic solutes. Ionic permeabilities through a large variety of ion channels have been precisely determined during the last decades. For obvious technical reasons, such investigations employed using ion channels in their fully open state. However novel findings show that some ion channels may undergo conformational changes characterize by an incomplete closing (subconducting states). In this respect our investigations focused on assessing the permeability of lysenin channels to monovalent cations in both fully open and subconducting conformations. In this endeavor we took advantage of the fact that lysenin channels achieve stable subconducting states in the presence of divalent metals and measured the transmembrane voltages resulted from chemical gradients for both conformations. The differences between ionic permeabilities for the two situations were interpreted as originating in changes of the electrostatic energy profile along the channel lumen upon conformational transitions.
Ionic Selectivity of Protein Channels in Subconducting States
The directed transport of ions via ion channels embedded into cell membranes is essential for nutrition, maintaining and creating electrical gradients, communication, and information processing and transmission. A large variety of physiological functions are ensured by channels that present selectivity for ionic solutes. Ionic permeabilities through a large variety of ion channels have been precisely determined during the last decades. For obvious technical reasons, such investigations employed using ion channels in their fully open state. However novel findings show that some ion channels may undergo conformational changes characterize by an incomplete closing (subconducting states). In this respect our investigations focused on assessing the permeability of lysenin channels to monovalent cations in both fully open and subconducting conformations. In this endeavor we took advantage of the fact that lysenin channels achieve stable subconducting states in the presence of divalent metals and measured the transmembrane voltages resulted from chemical gradients for both conformations. The differences between ionic permeabilities for the two situations were interpreted as originating in changes of the electrostatic energy profile along the channel lumen upon conformational transitions.