K⁺-dependent selectivity and external Ca²⁺ block of Shab K⁺ channels

PloS One
Elisa CarrilloFroylan Gómez-Lagunas

Abstract

Potassium channels allow the selective flux of K⁺ excluding the smaller, and more abundant in the extracellular solution, Na⁺ ions. Here we show that Shab is a typical K⁺ channel that excludes Na⁺ under bi-ionic, Na(o)/K(i) or Na(o)/Rb(i), conditions. However, when internal K⁺ is replaced by Cs⁺ (Na(o)/Cs(i)), stable inward Na⁺ and outward Cs⁺ currents are observed. These currents show that Shab selectivity is not accounted for by protein structural elements alone, as implicit in the snug-fit model of selectivity. Additionally, here we report the block of Shab channels by external Ca²⁺ ions, and compare the effect that internal K⁺ replacement exerts on both Ca²⁺ and TEA block. Our observations indicate that Ca²⁺ blocks the channels at a site located near the external TEA binding site, and that this pore region changes conformation under conditions that allow Na⁺ permeation. In contrast, the latter ion conditions do not significantly affect the binding of quinidine to the pore central cavity. Based on our observations and the structural information derived from the NaK bacterial channel, we hypothesize that Ca²⁺ is probably coordinated by main chain carbonyls of the pore's first K⁺-binding site.

References

May 1, 1974·Quarterly Reviews of Biophysics·C M Armstrong
Jan 1, 1980·The Journal of General Physiology·W Almers, C M Armstrong
Jul 15, 1995·The Journal of Physiology·S R Ikeda, S J Korn
Apr 1, 1994·Biophysical Journal·L HeginbothamR MacKinnon
Nov 1, 1993·Biophysical Journal·L Heginbotham, R MacKinnon
Jul 23, 1996·Proceedings of the National Academy of Sciences of the United States of America·D BeckerR Hedrich
Nov 14, 1997·The Journal of General Physiology·J G StarkusS H Heinemann
Dec 16, 1997·Proceedings of the National Academy of Sciences of the United States of America·K KhodakhahC M Armstrong
Mar 7, 1998·The Journal of General Physiology·T X Dang, E W McCleskey
Aug 5, 1998·The Journal of General Physiology·M Spassova, Z Lu
Sep 24, 1998·Biophysical Journal·A MelishchukC M Armstrong
Jun 3, 1999·The Journal of General Physiology·D ImmkeS J Korn
Nov 28, 2001·The Journal of General Physiology·F Gómez-Lagunas
Jan 2, 2003·Proceedings of the National Academy of Sciences of the United States of America·Froylan Gomez-LagunasClay M Armstrong
May 28, 2004·Nature Structural & Molecular Biology·Arthur Kornberg
Dec 2, 2004·The Journal of General Physiology·Toby W AllenBenoit Roux
May 24, 2005·Pflügers Archiv : European journal of physiology·Marco Ambriz-RivasFroylan Gomez-Lagunas
Jul 9, 2005·Science·Stephen B LongRoderick Mackinnon
Feb 10, 2006·Nature·Ning ShiYouxing Jiang
Jul 18, 2006·Biophysical Chemistry·Sergei Yu Noskov, Benoît Roux
Sep 20, 2007·Proceedings of the National Academy of Sciences of the United States of America·Amer AlamYouxing Jiang
Dec 29, 2010·Proceedings of the National Academy of Sciences of the United States of America·Mehabaw G DerebeYouxing Jiang
Jan 16, 2013·The Journal of General Physiology·Toshinori Hoshi, Clay M Armstrong

❮ Previous
Next ❯

Related Concepts

Related Feeds

Cardiac Conduction System

The cardiac conduction system is a specialized tract of myocardial cells responsible for maintaining normal cardiac rhythm. Discover the latest research on the cardiac conduction system here.