Anion-cation permeability correlates with hydrated counterion size in glycine receptor channels.

Biophysical Journal
Silas SugihartoP H Barry

Abstract

The functional role of ligand-gated ion channels depends critically on whether they are predominantly permeable to cations or anions. However, these, and other ion channels, are not perfectly selective, allowing some counterions to also permeate. To address the mechanisms by which such counterion permeation occurs, we measured the anion-cation permeabilities of different alkali cations, Li(+) Na(+), and Cs(+), relative to either Cl(-) or NO(3)(-) anions in both a wild-type glycine receptor channel (GlyR) and a mutant GlyR with a wider pore diameter. We hypothesized and showed that counterion permeation in anionic channels correlated inversely with an equivalent or effective hydrated size of the cation relative to the channel pore radius, with larger counterion permeabilities being observed in the wider pore channel. We also showed that the anion component of conductance was independent of the nature of the cation. We suggest that anions and counterion cations can permeate through the pore as neutral ion pairs, to allow the cations to overcome the large energy barriers resulting from the positively charged selectivity filter in small GlyR channels, with the permeability of such ion pairs being dependent on the effective hydrated...Continue Reading

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Citations

Mar 4, 2010·Pflügers Archiv : European journal of physiology·Silas SugihartoPeter H Barry
Feb 2, 2011·The Journal of Chemical Physics·Tamsyn A HilderShin-Ho Chung
Nov 23, 2013·Channels·Charles D CoxBoris Martinac
Jul 7, 2016·The Journal of Biological Chemistry·Constanze RaltschevMarcus Semtner
Jul 30, 2014·The Journal of Physical Chemistry. B·Hao DongGiacomo Fiorin
Jun 23, 2020·The Journal of Physical Chemistry. B·F K A GregsonJ P Reid

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