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Single HERG delayed rectifier K+ channels expressed in Xenopus oocytes
A Zou1, M E Curran, M T Keating
1Cardiology Division, University of Utah Health Sciences Center, Salt Lake City 84132, USA.
The American Journal of Physiology
|March 1, 1997
Summary
The human Ether-à-go-go-Related Gene (HERG) potassium channel, crucial for heart repolarization, exhibits single-channel properties mirroring cardiac I(Kr) currents. HERG channel block by MK-499 occurs from the cytoplasmic side.
Area of Science:
- Molecular Biology
- Cardiovascular Physiology
- Ion Channel Biophysics
Background:
- The human Ether-à-go-go-Related Gene (HERG) encodes a potassium channel critical for cardiac repolarization.
- The rapidly activating component of the delayed rectifier potassium current (I(Kr)) is essential for maintaining normal heart rhythm.
Purpose of the Study:
- To characterize the single-channel properties of HERG potassium channels expressed in Xenopus oocytes.
- To investigate the mechanism of block of HERG channels by the antiarrhythmic drug MK-499.
Main Methods:
- Xenopus oocytes were used to express HERG channels.
- Single-channel currents were recorded using cell-attached and inside-out patch-clamp techniques.
- The effects of MK-499 on HERG channel activity were analyzed.
Main Results:
- Single HERG channel conductance was determined at various potentials, showing distinct values for negative and positive potentials.
- Mean open and closed times for single HERG channels were measured.
- MK-499 demonstrated block of HERG channels, with faster block development in inside-out patches, indicating cytoplasmic access.
Conclusions:
- The single-channel properties of expressed HERG channels closely resemble those of native I(Kr) channels in cardiac myocytes.
- These findings support the hypothesis that HERG proteins coassemble to form functional I(Kr) channels.
- Blockade of HERG channels by MK-499 occurs from the cytoplasmic side of the membrane.