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Internal and external TEA block in single cloned K+ channels
G E Kirsch1, M Taglialatela, A M Brown
1Department of Anesthesiology, Baylor College of Medicine, Houston, Texas 77030.
The American Journal of Physiology
|October 1, 1991
Summary
Tetraethylammonium (TEA) blocks potassium channels from both sides of the membrane. Internal TEA blocks open channels within the electric field, defining the pore
Area of Science:
- Molecular biology
- Biophysics
- Neuroscience
Background:
- Tetraethylammonium (TEA) is a common blocker used to study voltage-dependent potassium channels.
- Understanding TEA's interaction with potassium channels provides insights into channel structure and function.
Purpose of the Study:
- To investigate the molecular mechanism of tetraethylammonium (TEA) block in the rat brain potassium channel RCK2.
- To characterize the binding sites and kinetics of TEA block at the intracellular and extracellular surfaces.
Main Methods:
- Single-channel patch-clamp electrophysiology in Xenopus oocytes expressing RCK2 channels.
- Application of TEA and tetrapentylammonium to intracellular and extracellular sides of membrane patches.
- Analysis of channel open time, closed interval duration, and single-channel amplitude.
Main Results:
- Intracellular TEA decreased channel open time and prolonged closed intervals, selectively blocking open channels.
- Extracellular TEA reduced apparent single-channel amplitude with slower block kinetics.
- Voltage dependence of internal TEA block localized the binding site 25% into the membrane from the cytoplasmic side.
Conclusions:
- Internal and external TEA binding sites delineate the inner and outer boundaries of the RCK2 channel's aqueous pore.
- TEA acts as a molecular ruler to probe the dimensions of the potassium channel pore.
- The distinct binding kinetics and voltage sensitivities suggest different interactions with the channel pore.