The Journal of General Physiology
Axon Instruments microelectrode amplifiers
  Home | Help | Feedback | Subscriptions | Archive | Search | Table of Contents
Published online June 25, 2007
doi:10.1085/jgp.200709802
The Journal of General Physiology, Vol. 130, No. 1, 83-97
The Rockefeller University Press, 0022-1295 $30.00
© 2007 Schroeder et al.
This Article
Right arrow Full Text
Right arrow PDF (Full Text)
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 Schroeder, I.
Right arrow Articles by Hansen, U.-P.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Schroeder, I.
Right arrow Articles by Hansen, U.-P.
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?

ARTICLE

 Saturation and Microsecond Gating of Current Indicate Depletion-induced Instability of the MaxiK Selectivity Filter



Indra Schroeder and Ulf-Peter Hansen

Department of Structural Biology, University of Kiel, 24098 Kiel, Germany

Correspondence to Ulf-Peter Hansen: uphansen{at}zbm.uni-kiel.de

Patch clamp experiments on single MaxiK channels expressed in HEK293 cells were performed with a high temporal resolution (50-kHz filter) in symmetrical solutions with 50, 150, or 400 mM KCl and 2.5 mM CaCl2 and 2.5 mM MgCl2. At membrane potentials >+100 mV, the single-channel current showed a negative slope resistance, concomitantly with a flickery block, which was not influenced by Ca2+ or Mg2+. The analysis of the amplitude histograms by beta distributions revealed that current in this voltage range was reduced by two effects: rate limitation at the cytosolic side of the pore and gating with rate constants 10–20-fold higher than the cutoff frequency of the filter (i.e., dwell times in the microsecond range). The data were analyzed in terms of a model that postulates a coupling between both effects; if the voltage over the selectivity filter withdraws ions from the cavity at a higher rate than that of refilling from the cytosol, the selectivity filter becomes instable because of ion depletion, and current is interrupted by the resulting flickering. The fit of the IV curves revealed a characteristic voltage of 35 mV. In contrast, the voltage dependence of the gating factor R, i.e., the ratio between true and apparent single-channel current, could be fitted by exponentials with a characteristic voltage of 60 mV, suggesting that only part of the transmembrane potential is felt by the flux through the selectivity filter.


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
 Mol. Pharmacol.Home page
A. Klose, T. Huth, and C. Alzheimer

Mol. Pharmacol., November 1, 2008; 74(5): 1203 - 1214.
[Abstract] [Full Text] [PDF]

Home page
 Biophys. JHome page
G. V. Miloshevsky and P. C. Jordan
Conformational Changes in the Selectivity Filter of the Open-State KcsA Channel: An Energy Minimization Study
Biophys. J., October 1, 2008; 95(7): 3239 - 3251.
[Abstract] [Full Text] [PDF]

Home page
 JGPHome page
I. Schroeder and U.-P. Hansen
Tl+-induced {micro}s Gating of Current Indicates Instability of the MaxiK Selectivity Filter as Caused by Ion/Pore Interaction
J. Gen. Physiol., March 31, 2008; 131(4): 365 - 378.
[Abstract] [Full Text] [PDF]


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