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The cooperative voltage sensor motion that gates a potassium channel
Medha Pathak1, Lisa Kurtz, Francesco Tombola
1Biophysics Graduate Group, University of California, Berkeley, Berkeley, CA 94720, USA.
The Journal of General Physiology
|December 30, 2004
Summary
Voltage-gated channel S4 helices undergo a novel cooperative movement during opening, directly driving gate function. This finding reveals a more complex coupling mechanism between voltage sensing and ion channel gating.
Area of Science:
- Molecular Biology
- Biophysics
- Ion Channel Physiology
Background:
- Voltage-gated channels control ion flow across cell membranes.
- S4 helices are crucial for voltage sensing and channel gating.
- Previous models suggested independent S4 movement, but cooperative roles were implied.
Purpose of the Study:
- To investigate the precise role of S4 helices in the gating mechanism of voltage-gated channels.
- To elucidate the coupling between voltage sensing and channel opening.
- To identify novel movements of S4 during channel activation.
Main Methods:
- Utilized a Shaker channel mutant (ILT channel) that separates activation and cooperative opening steps.
- Employed fluorescence monitoring to track structural rearrangements.
- Energetically isolated distinct gating steps for detailed analysis.
Main Results:
- Observed a previously unrecognized cooperative movement of S4 helices during channel opening.
- Demonstrated that this S4 gating motion is coupled to the internal S6 gate.
- Found coupling to two distinct forms of slow inactivation.
Conclusions:
- S4 helices play a direct and active role in driving the opening and closing of ion channel gates.
- The gating motion of S4, not just its conformational change, is key to channel function.
- This provides a more refined understanding of voltage-sensing to gating coupling mechanisms.