|
|
|
|
|
|
|
||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
The Journal of General Physiology, Vol 89, 841-872, Copyright © 1987 by The Rockefeller University Press
ARTICLES |
WN Green, LB Weiss and OS Andersen
Batrachotoxin-modified, voltage-dependent sodium channels from canine forebrain were incorporated into planar lipid bilayers. Single-channel conductances were studied for [Na+] ranging between 0.02 and 3.5 M. Typically, the single-channel currents exhibited a simple two-state behavior, with transitions between closed and fully open states. Two other conductance states were observed: a subconductance state, usually seen at [NaCl] greater than or equal to 0.5 M, and a flickery state, usually seen at [NaCl] less than or equal to 0.5 M. The flickery state became more frequent as [NaCl] was decreased below 0.5 M. The K+/Na+ permeability ratio was approximately 0.16 in 0.5 and 2.5 M salt, independent of the Na+ mole fraction, which indicates that there are no interactions among permeant ions in the channels. Impermeant and permeant blocking ions (tetraethylammonium, Ca++, Zn++, and K+) have different effects when added to the extracellular and intracellular solutions, which indicates that the channel is asymmetrical and has at least two cation-binding sites. The conductance vs. [Na+] relation saturated at high concentrations, but could not be described by a Langmuir isotherm, as the conductance at low [NaCl] is higher than predicted from the data at [NaCl] greater than or equal to 1.0 M. At low [NaCl] (less than or equal to 0.1 M), increasing the ionic strength by additions of impermeant monovalent and divalent cations reduced the conductance, as if the magnitude of negative electrostatic potentials at the channel entrances were reduced. The conductances were comparable for channels in bilayers that carry a net negative charge and bilayers that carry no net charge. Together, these results lead to the conclusion that negative charges on the channel protein near the channel entrances increase the conductance, while lipid surface charges are less important.
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
This article has been cited by other articles:
|
|
 |
|
  W. Xiong, Y. Z. Farukhi, Y. Tian, D. DiSilvestre, R. A. Li, and G. F. Tomaselli A conserved ring of charge in mammalian Na+ channels: a molecular regulator of the outer pore conformation during slow inactivation J. Physiol., November 1, 2006; 576(3): 739 - 754. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Khan, J. W. Kyle, D. A. Hanck, G. M. Lipkind, and H. A. Fozzard Isoform-dependent interaction of voltage-gated sodium channels with protons J. Physiol., October 15, 2006; 576(2): 493 - 501. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S.-H. Yeh, H.-K. Chang, and R.-C. Shieh Electrostatics in the Cytoplasmic Pore Produce Intrinsic Inward Rectification in Kir2.1 Channels J. Gen. Physiol., November 28, 2005; 126(6): 551 - 562. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
W. Xiong, R. A. Li, Y. Tian, and G. F. Tomaselli Molecular Motions of the Outer Ring of Charge of the Sodium Channel: Do They Couple to Slow Inactivation? J. Gen. Physiol., August 25, 2003; 122(3): 323 - 332. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. Hui, D. McIntyre, and R. J. French Conotoxins as Sensors of Local pH and Electrostatic Potential in the Outer Vestibule of the Sodium Channel J. Gen. Physiol., June 30, 2003; 122(1): 63 - 79. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. B. Park, H. J. Kim, P. D. Ryu, and E. Moczydlowski Effect of Phosphatidylserine on Unitary Conductance and Ba2+ Block of the BK Ca2+-activated K+ Channel: Re-examination of the Surface Charge Hypothesis J. Gen. Physiol., April 28, 2003; 121(5): 375 - 398. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 T. E. Decoursey Voltage-Gated Proton Channels and Other Proton Transfer Pathways Physiol Rev, April 1, 2003; 83(2): 475 - 579. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 H. Musa and R. D. Veenstra Voltage-Dependent Blockade of Connexin40 Gap Junctions by Spermine Biophys. J., January 1, 2003; 84(1): 205 - 219. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C.-C. Kuo, T.-J. Lin, and C.-P. Hsieh Effect of Na+ Flow on Cd2+ Block of Tetrodotoxin-resistant Na+ Channels J. Gen. Physiol., July 30, 2002; 120(2): 159 - 172. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 K. Turnheim, J. Gruber, C. Wachter, and V. Ruiz-Gutierrez Membrane phospholipid composition affects function of potassium channels from rabbit colon epithelium Am J Physiol Cell Physiol, July 1, 1999; 277(1): C83 - C90. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R. Horn The dual role of calcium: Pore blocker and modulator of gating PNAS, March 30, 1999; 96(7): 3331 - 3332. [Full Text] [PDF]
|
|
|
|
