The Journal of General Physiology
World Precision Insruments
  Home | Help | Feedback | Subscriptions | Archive | Search | Table of Contents
Published 22 February 2002. doi:10.1085/jgp.119.3.235
This Article
Right arrow Full Text
Right arrow Full Text (PDF, 1096K)
Right arrow PPT slides of all figures
Right arrow Correction (v119,p391)
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 Rakowski, R. F.
Right arrow Articles by De Weer, P.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Rakowski, R. F.
Right arrow Articles by De Weer, 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?
© Rockefeller University Press, 0022-1295/2002/3/235/ $5.00
Journal of General Physiology, Volume 119, Number 3, March 2002 235-250

Original Article

 Single Ion Occupancy and Steady-state Gating of Na Channels in Squid Giant Axon

Robert F. Rakowski, David C. Gadsby and Paul De Weer

Marine Biological Laboratory, Woods Hole, Massachusetts 02543

Address correspondence to Dr. R.F. Rakowski, Department of Biological Sciences, Ohio University, Irvine Hall, Athens, OH 45701. Fax: (740) 593-0300; E-mail: rakowski{at}ohio.edu

The properties of the small fraction of tetrodotoxin (TTX)-sensitive Na channels that remain open in the steady state were studied in internally dialyzed voltage clamped squid giant axons. The observed Ussing flux ratio exponent (n') of 0.97 ± 0.03 (calculated from simultaneous measurements of TTX-sensitive current and 22Na efflux) and nonindependent behavior of Na current at high internal [Na] are explained by a one-site ("1s") permeation model characterized by a single effective binding site within the channel pore in equilibrium with internal Na ions (apparent equilibrium dissociation constant KNai(0) = 0.61 ± 0.08 M). Steady-state open probability of the TTX-sensitive channels can be modeled by the product pap{infty}, where pa represents voltage-dependent activation described by a Boltzmann distribution with midpoint Va = -7 mV and effective valence za = 3.2 (Vandenberg, C.A., and F. Bezanilla. 1991. Biophys. J. 60:1499–1510) coupled to voltage-independent inactivation by an equilibrium constant (Bezanilla, F., and C.M. Armstrong. 1977. J. Gen. Physiol. 70:549–566) Keq = 770. The factor p{infty} represents voltage-dependent inactivation with empirical midpoint V{infty}= -83 ± 5 mV and effective valence z{infty} = 0.55 ± 0.03. The composite pap{infty}1s model describes the steady-state voltage dependence of the persistent TTX-sensitive current well.

Key Words: inactivation • tetrodotoxin • nonindependence • flux ratio • open probability


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
D. Boda, W. Nonner, M. Valisko, D. Henderson, B. Eisenberg, and D. Gillespie
Steric Selectivity in Na Channels Arising from Protein Polarization and Mobile Side Chains
Biophys. J., September 15, 2007; 93(6): 1960 - 1980.
[Abstract] [Full Text] [PDF]

Home page
 JGPHome page
R.F. Rakowski, P. Artigas, F. Palma, M. Holmgren, P. De Weer, and D. C. Gadsby
Sodium Flux Ratio in Na/K Pump-Channels Opened by Palytoxin
J. Gen. Physiol., July 1, 2007; 130(1): 41 - 54.
[Abstract] [Full Text] [PDF]

Home page
 Physiol. Rev.Home page
W. Ulbricht
Sodium Channel Inactivation: Molecular Determinants and Modulation
Physiol Rev, October 1, 2005; 85(4): 1271 - 1301.
[Abstract] [Full Text] [PDF]

Home page
 Proc. Natl. Acad. Sci. USAHome page
Z. Liu, W. Song, and K. Dong
Persistent tetrodotoxin-sensitive sodium current resulting from U-to-C RNA editing of an insect sodium channel
PNAS, August 10, 2004; 101(32): 11862 - 11867.
[Abstract] [Full Text] [PDF]

Home page
 J. Neurophysiol.Home page
J. R. Clay
On the Persistent Sodium Current in Squid Giant Axons
J Neurophysiol, January 1, 2003; 89(1): 640 - 644.
[Abstract] [Full Text] [PDF]


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