The Journal of General Physiology
VISIT JCB ONLINE!
  Home | Help | Feedback | Subscriptions | Archive | Search | Table of Contents
This Article
Right arrow Full Text
Right arrow Full Text (PDF, 222K)
Right arrow PPT slides of all figures
Right arrow Alert me when this article is cited
Right arrow Citation Map
Services
Right arrow Email this article
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new content in the JGP
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via CrossRef
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Stampe, P.
Right arrow Articles by Begenisich, T.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Stampe, P.
Right arrow Articles by Begenisich, T.
Right arrowPubmed/NCBI databases
*Compound via MeSH
*Substance via MeSH
Hazardous Substances DB
*POTASSIUM
Social Bookmarking
Add to CiteULike   Add to Complore   Add to Connotea   Add to Del.icio.us   Add to Digg   Add to Reddit   Add to Technorati  
What's this?

J. Gen. Physiol., Volume 112, Number 4, October 1, 1998 475-484

Nonindependent K+ Movement through the Pore in IRK1 Potassium Channels

Per Stampe, Jorge Arreola, Patricia Pérez-Cornejo, and Ted Begenisich

From the Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, New York 14642

We measured unidirectional K+ in- and efflux through an inward rectifier K channel (IRK1) expressed in Xenopus oocytes. The ratio of these unidirectional fluxes differed significantly from expectations based on independent ion movement. In an extracellular solution with a K+ concentration of 25 mM, the data were described by a Ussing flux-ratio exponent, n', of ~2.2 and was constant over a voltage range from -50 to -25 mV. This result indicates that the pore of IRK1 channels may be simultaneously occupied by at least three ions. The IRK1 n' value of 2.2 is significantly smaller than the value of 3.5 obtained for Shaker K channels under identical conditions. To determine if other permeation properties that reflect multi-ion behavior differed between these two channel types, we measured the conductance (at 0 mV) of single IRK1 channels as a function of symmetrical K+ concentration. The conductance could be fit by a saturating hyperbola with a half-saturation K+ activity of 40 mM, substantially less than the reported value of 300 mM for Shaker K channels. We investigated the ability of simple permeation models based on absolute reaction rate theory to simulate IRK1 current-voltage, conductance, and flux-ratio data. Certain classes of four-barrier, three-site permeation models are inconsistent with the data, but models with high lateral barriers and a deep central well were able to account for the flux-ratio and single channel data. We conclude that while the pore in IRK1 and Shaker channels share important similarities, including K+ selectivity and multi-ion occupancy, they differ in other properties, including the sensitivity of pore conductance to K+ concentration, and may differ in the number of K+ ions that can simultaneously occupy the pore: IRK1 channels may contain three ions, but the pore in Shaker channels can accommodate four or more ions.

Key words: ion permeation;  unidirectional flux-ratio;  single channel conductance


Add to CiteULike CiteULike   Add to Complore Complore   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us   Add to Digg Digg   Add to Reddit Reddit   Add to Technorati Technorati    What's this?


This article has been cited by other articles:


Home page
 Biophys. JHome page
T. Vora, D. Bisset, and S.-H. Chung
Conduction of Na+ and K+ through the NaK Channel: Molecular and Brownian Dynamics Studies
Biophys. J., August 15, 2008; 95(4): 1600 - 1611.
[Abstract] [Full Text] [PDF]

Home page
 JGPHome page
N. D'Avanzo, H. C. Cho, I. Tolokh, R. Pekhletski, I. Tolokh, C. Gray, S. Goldman, and P. H. Backx
Conduction through the Inward Rectifier Potassium Channel, Kir2.1, Is Increased by Negatively Charged Extracellular Residues
J. Gen. Physiol., April 25, 2005; 125(5): 493 - 503.
[Abstract] [Full Text] [PDF]

Home page
 JGPHome page
H.-G. Shin and Z. Lu
Mechanism of the Voltage Sensitivity of IRK1 Inward-rectifier K+ Channel Block by the Polyamine Spermine
J. Gen. Physiol., March 28, 2005; 125(4): 413 - 426.
[Abstract] [Full Text] [PDF]

Home page
 JGPHome page
H. T. Kurata, L. R. Phillips, T. Rose, G. Loussouarn, S. Herlitze, H. Fritzenschaft, D. Enkvetchakul, C. G. Nichols, and T. Baukrowitz
Molecular Basis of Inward Rectification: Polyamine Interaction Sites Located by Combined Channel and Ligand Mutagenesis
J. Gen. Physiol., October 25, 2004; 124(5): 541 - 554.
[Abstract] [Full Text] [PDF]

Home page
 Biophys. JHome page
D. L. Prole and N. V. Marrion
Ionic Permeation and Conduction Properties of Neuronal KCNQ2/KCNQ3 Potassium Channels
Biophys. J., March 1, 2004; 86(3): 1454 - 1469.
[Abstract] [Full Text] [PDF]

Home page
 JGPHome page
D. Guo, Y. Ramu, A. M. Klem, and Z. Lu
Mechanism of Rectification in Inward-rectifier K+ Channels
J. Gen. Physiol., March 31, 2003; 121(4): 261 - 276.
[Abstract] [Full Text] [PDF]

Home page
 Biophys. JHome page
S.-H. Chung, T. W. Allen, and S. Kuyucak
Modeling Diverse Range of Potassium Channels with Brownian Dynamics
Biophys. J., July 1, 2002; 83(1): 263 - 277.
[Abstract] [Full Text] [PDF]

Home page
 J. Biol. Chem.Home page
R.-C. Shieh, J.-C. Chang, and C.-C. Kuo
K+ Binding Sites and Interactions between Permeating K+ Ions at the External Pore Mouth of an Inward Rectifier K+ Channel (Kir2.1)
J. Biol. Chem., June 18, 1999; 274(25): 17424 - 17430.
[Abstract] [Full Text] [PDF]


  Home | Help | Feedback | Subscriptions | Archive | Search | Table of Contents