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Gating current noise produced by elementary transitions in Shaker potassium channels
D Sigg1, E Stefani, F Bezanilla
1Department of Physiology, School of Medicine, University of California at Los Angeles 90024.
Science (New York, N.Y.)
|April 22, 1994
Summary
Researchers measured fluctuations in Shaker potassium channel gating currents to understand charge movement. They found channel activation involves two stages, with the second stage featuring significant charge transfer.
Area of Science:
- Biophysics
- Molecular Biology
- Neuroscience
Background:
- Voltage-sensitive ion channels are crucial for cellular electrical signaling.
- Gating currents reflect the movement of charges within these channels during activation.
- Understanding charge movement is key to elucidating channel gating mechanisms.
Purpose of the Study:
- To investigate the nature of elementary charge movements during voltage-sensitive ion channel gating.
- To quantify the magnitude and timing of charge transitions in Shaker potassium channels.
- To characterize the stages of channel activation based on gating current fluctuations.
Main Methods:
- Expressing Shaker potassium channels in Xenopus oocytes.
- Recording gating currents with high bandwidth to resolve rapid fluctuations.
- Analyzing the variance of gating currents to estimate elementary charge movements.
Main Results:
- Channel activation proceeds in two distinct sequential stages.
- The first stage involves numerous fast transitions with minimal charge contribution.
- The second stage dominates gating current fluctuations, involving discrete, correlated transitions, with at least one carrying >= 2.4 elementary charges.
Conclusions:
- Gating current fluctuations reveal discrete charge movements during channel activation.
- Shaker potassium channel activation involves a multi-step process with significant charge redistribution in later stages.
- The findings provide insights into the physical basis of voltage sensing in ion channels.