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Membrane insertion of a potassium-channel voltage sensor
Tara Hessa1, Stephen H White, Gunnar von Heijne
1Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden.
Science (New York, N.Y.)
|February 1, 2005
Summary
The voltage gating mechanism in potassium (K+) channels is debated. Our study suggests the S4 helix is near the membrane insertion threshold, supporting the paddle model for K+ channel function.
Area of Science:
- Biophysics
- Molecular Biology
- Membrane Protein Dynamics
Background:
- The voltage gating mechanism of potassium (K+) channels remains controversial.
- Two main models exist: the paddle model and models where the S4 helix is shielded from lipid contact.
Purpose of the Study:
- To investigate the membrane insertion energetics of the K+ channel S4 helix.
- To evaluate the consistency of experimental findings with the paddle model.
Main Methods:
- Measurement of the apparent free energy of S4 helix insertion into the endoplasmic reticulum membrane.
Main Results:
- The S4 helix was found to be poised near the threshold for efficient bilayer insertion.
- This finding indicates that S4 is not deeply shielded from the lipid environment.
Conclusions:
- The experimental data do not contradict the paddle model for K+ channel voltage gating.
- The high charge content of S4 is compatible with its near-threshold membrane insertion behavior.
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