|
|
|
|
|
|
|
||
Original Article |
zhelu{at}mail.med.upenn.edu
To understand the role of permeating ions in determining blocking ion–induced rectification, we examined block of the ROMK1 inward-rectifier K+ channel by intracellular tetraethylammonium in the presence of various alkali metal ions in both the extra- and intracellular solutions. We found that the channel exhibits different degrees of rectification when different alkali metal ions (all at 100 mM) are present in the extra- and intracellular solution. A quantitative analysis shows that an external ion site in the ROMK1 pore binds various alkali metal ions (Na+, K+, Rb+, and Cs+) with different affinities, which can in turn be altered by the binding of different permeating ions at an internal site through a nonelectrostatic mechanism. Consequently, the external site is saturated to a different level under the various ionic conditions. Since rectification is determined by the movement of all energetically coupled ions in the transmembrane electrical field along the pore, different degrees of rectification are observed in various combinations of extra- and intracellular permeant ions. Furthermore, the external and internal ion-binding sites in the ROMK1 pore appear to have different ion selectivity: the external site selects strongly against the smaller Na+, but only modestly among the three larger ions, whereas the internal site interacts quite differently with the larger K+ and Rb+ ions.
Key Words: inward-rectifier K+ channel • rectification • ionic blocker • ion selectivity • tetraethylammonium
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Facebook 
Reddit 
Technorati 
Twitter What's this?
This article has been cited by other articles:
|
|
 |
|
  J. R. Martinez-Francois and Z. Lu Intrinsic versus extrinsic voltage sensitivity of blocker interaction with an ion channel pore J. Gen. Physiol., January 25, 2010; 135(2): 149 - 167. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 X. Tao, J. L. Avalos, J. Chen, and R. MacKinnon Crystal Structure of the Eukaryotic Strong Inward-Rectifier K+ Channel Kir2.2 at 3.1 A Resolution Science, December 18, 2009; 326(5960): 1668 - 1674. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
X.-D. Zhang, P.-Y. Tseng, W.-P. Yu, and T.-Y. Chen Blocking Pore-open Mutants of CLC-0 by Amphiphilic Blockers J. Gen. Physiol., December 29, 2008; 133(1): 43 - 58. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. E. Contreras and M. Holmgren Access of Quaternary Ammonium Blockers to the Internal Pore of Cyclic Nucleotide-gated Channels: Implications for the Location of the Gate J. Gen. Physiol., April 24, 2006; 127(5): 481 - 494. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
U. Banderali, H. Klein, L. Garneau, M. Simoes, L. Parent, and R. Sauve New Insights on the Voltage Dependence of the KCa3.1 Channel Block by Internal TBA J. Gen. Physiol., September 27, 2004; 124(4): 333 - 348. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. Guo and Z. Lu Interaction Mechanisms between Polyamines and IRK1 Inward Rectifier K+ Channels J. Gen. Physiol., October 27, 2003; 122(5): 485 - 500. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 X. Gong and P. Linsdell Coupled movement of permeant and blocking ions in the CFTR chloride channel pore J. Physiol., June 1, 2003; 549(2): 375 - 385. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Zhang, S. J Kehl, and D. Fedida Modulation of human ether-a-go-go-related K+ (HERG) channel inactivation by Cs+ and K+ J. Physiol., May 1, 2003; 548(3): 691 - 702. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
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]
|
|
|
|
|
|
F. Gomez-Lagunas Na+ Interaction with the Pore of Shaker B K+ Channels: Zero and Low K+ Conditions J. Gen. Physiol., December 1, 2001; 118(6): 639 - 648. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. Guo and Z. Lu Kinetics of Inward-Rectifier K+ Channel Block by Quaternary Alkylammonium Ions: Dimension and Properties of the Inner Pore J. Gen. Physiol., May 1, 2001; 117(5): 395 - 406. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. Thompson and T. Begenisich Affinity and Location of an Internal K+ Ion Binding Site in Shaker K Channels J. Gen. Physiol., May 1, 2001; 117(5): 373 - 384. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 X. Wang, A. Y. Xiao, T. Ichinose, and S. P. Yu Effects of Tetraethylammonium Analogs on Apoptosis and Membrane Currents in Cultured Cortical Neurons J. Pharmacol. Exp. Ther., November 1, 2000; 295(2): 524 - 530. [Abstract] [Full Text]
|
|
|
|
|
|
H. Xu, Z. Yang, N. Cui, S. Chanchevalap, W. W Valesky, and C. Jiang A single residue contributes to the difference between Kir4.1 and Kir1.1 channels in pH sensitivity, rectification and single channel conductance J. Physiol., October 15, 2000; 528(2): 267 - 277. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. Guo and Z. Lu Mechanism of Irk1 Channel Block by Intracellular Polyamines J. Gen. Physiol., June 1, 2000; 115(6): 799 - 814. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. Thompson and T. Begenisich Interaction between Quaternary Ammonium Ions in the Pore of Potassium Channels: Evidence against an Electrostatic Repulsion Mechanism J. Gen. Physiol., June 1, 2000; 115(6): 769 - 782. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. Immke and S. J. Korn Ion-Ion Interactions at the Selectivity Filter: Evidence from K+-Dependent Modulation of Tetraethylammonium Efficacy in Kv2.1 Potassium Channels J. Gen. Physiol., April 1, 2000; 115(4): 509 - 518. [Abstract] [Full Text] [PDF]
|
|
|
|
