The selectivity of different external binding sites for quaternary ammonium ions in cloned potassium channels

1995 ◽  
Vol 430 (5) ◽  
pp. 672-681 ◽  
Author(s):  
W. Jarolimek ◽  
K. V. Soman ◽  
M. Alam ◽  
A. M. Brown
Keyword(s):  
Potassium Channels ◽  
Quaternary Ammonium ◽  
Binding Sites ◽  
Ammonium Ions ◽  
Quaternary Ammonium Ions

scholarly journals Interaction between Quaternary Ammonium Ions in the Pore of Potassium Channels

2000 ◽  
Vol 115 (6) ◽  
pp. 769-782 ◽  
Author(s):  
Jill Thompson ◽  
Ted Begenisich
Keyword(s):  
Potassium Channels ◽  
Long Range ◽  
Quaternary Ammonium ◽  
Binding Sites ◽  
Electrostatic Interactions ◽  
Electrostatic Repulsion ◽  
Ammonium Ions ◽  
Shaker Channels ◽  
Quaternary Ammonium Ions ◽  
Na Ions

We have examined the interaction between internal and external ions in the pore of potassium channels. We found that external tetraethylammonium was able to antagonize block of Shaker channels by internal TEA when the external and internal solutions contained K+ ions. This antagonism was absent in solutions with Rb+ as the only permeant ion. An externally applied trivalent TEA analogue, gallamine, was less effective than the monovalent TEA in inhibiting block by internal TEA. In addition, block by external TEA was little affected by changes in the concentration of internal K+ ions, but was increased by the presence of internal Na+ ions in the pore. These results demonstrate that external and internal TEA ions, likely located at opposite ends of the pore selectivity filter, do not experience a mutual electrostatic repulsion. We found that these results can be simulated by a simple 4-barrier-3-site permeation model in which ions compete for available binding sites without long-range electrostatic interactions.

scholarly journals The Inner Quaternary Ammonium Ion Receptor in Potassium Channels of the Node of Ranvier

1972 ◽  
Vol 59 (4) ◽  
pp. 388-400 ◽  
Author(s):  
Clay M. Armstrong ◽  
Bertil Hille
Keyword(s):  
Potassium Channels ◽  
Quaternary Ammonium ◽  
Node Of Ranvier ◽  
Nerve Fibers ◽  
Ammonium Ion ◽  
Ammonium Ions ◽  
Myelinated Nerve ◽  
Quaternary Ammonium Ions ◽  
Activation Gate ◽  
Almost All

Quaternary ammonium ions were applied to the inside of single myelinated nerve fibers by diffusion from a cut end. The resulting block of potassium channels in the node of Ranvier was studied under voltage-clamp conditions. The results agree in almost all respects with similar studies by Armstrong of squid giant axons. With tetraethylammonium ion (TEA), pentyltriethylammonium ion (C5), or nonyltriethylammonium ion (C9) inside the node, potassium current during a depolarization begins to rise at the normal rate, reaches a peak, and then falls again. This unusual inactivation is more complete with C9 than with TEA. Larger depolarizations give more block. Thus the block of potassium channels grows with time and voltage during a depolarization. The block reverses with repolarization, but for C9 full reversal takes seconds at -75 mv. The reversal is faster in 120 mM KCl Ringer's and slower during a hyperpolarization to -125 mv. All of these effects contrast with the time and voltage-independent block of potassium, channels seen with external quaternary ammonium ions on the node of Ranvier. External TEA, C5, and C9 block without inactivation. The external quaternary ammonium ion receptor appears to be distinct from the inner one. Apparently the inner quaternary ammonium ion receptor can be reached only when the activation gate for potassium channels is open. We suggest that the inner receptor lies within the channel and that the channel is a pore with its activation gate near the axoplasmic end.

scholarly journals Extraction of SO3H-containing iron (III) complexes with quaternary ammonium ions

1968 ◽  
Vol 17 (5) ◽  
pp. 616-621 ◽  
Author(s):  
Hitoshi KOHARA ◽  
Nobuhiko ISHIBASHI ◽  
Akira YOSHIDA
Keyword(s):  
Quaternary Ammonium ◽  
Ammonium Ions ◽  
Quaternary Ammonium Ions
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