PMID: 7545280May 1, 1995Paper

Multiple ion binding sites in Ih channels of rod photoreceptors from tiger salamanders

Pflügers Archiv : European journal of physiology
L P Wollmuth

Abstract

The mechanism of ion permeation in K+/Na(+)-permeable Ih channels of tiger salamander rod photoreceptors was investigated using the whole-cell voltage-clamp technique. Ih channels showed features indicative of pores with multiple ion binding sites: in mixtures of K+ and thallium (T1+), the amplitude of the time-dependent current showed an anomalous mole fraction dependence, and K+ permeation was blocked by other permeant ions (with K0.5 values: T1+, 44 microM; Rb+, 220 microM and NH4+, 1100 microM) as well as by essentially impermeant ions (Cs+, 22 microM Ba2+, 9200 microM) which apparently block Ih by binding in the pore. In contrast, Na+ had little blocking action on K+ permeation. The block by all of these ions was sensitive to external K+ with the block by Cs+ being the least sensitive. Na+ was more effective than K+ in reducing the block by T1+, Rb+ and NH4+, but was less effective for the block by Cs+ and Ba2+. The blocking action of Cs+ and Ba2+ was non-competitive, suggesting that they block Ih channels at independent sites. Based on the efficacy of block by the different ions, the degree to which K+ and Na+ antagonize this block and the noncompetitive blocking action of Cs+ and Ba2+, the permeation pathway of Ih channe...Continue Reading

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Citations

Jun 27, 2002·The Journal of General Physiology·Annalisa BucchiDario DiFrancesco
Feb 14, 2008·The Journal of General Physiology·Alex K Lyashchenko, Gareth R Tibbs
Feb 22, 2001·Annual Review of Physiology·U B Kaupp, R Seifert
Jan 22, 2005·European Journal of Pharmacology·Ingrid van WelieJohannes A van Hooft
Oct 16, 2004·Journal of Neurophysiology·David CiaSerge Picaud
Jul 18, 2002·The Journal of Biological Chemistry·Vincenzo MacriEric A Accili

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