Calibrated Measurement of Gating-Charge Arginine Displacement in the KvAP Voltage-Dependent K+ Channel

Abstract

Voltage-dependent ion channels open and conduct ions in response to changes in cell-membrane voltage. The voltage sensitivity of these channels arises from the motion of charged arginine residues located on the S4 helices of the channel's voltage sensors. In KvAP, a prokaryotic voltage-dependent K+ channel, the S4 helix forms part of a helical hairpin structure, the voltage-sensor paddle. We have measured the membrane depth of residues throughout the KvAP channel using avidin accessibility to different-length tethered biotin reagents. From these measurements, we have calibrated the tether lengths and derived the thickness of the membrane that forms a barrier to avidin penetration, allowing us to determine the magnitude of displacement of the voltage-sensor paddles during channel gating. Here we show that the voltage-sensor paddles are highly mobile compared to other regions of the channel and transfer the gating-charge arginines 15-20 A through the membrane to open the pore.

DOI: 10.1016/j.cell.2005.08.041

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@article{Ruta2005CalibratedMO, title={Calibrated Measurement of Gating-Charge Arginine Displacement in the KvAP Voltage-Dependent K+ Channel}, author={Vanessa Ruta and Jiayun Chen and Roderick MacKinnon}, journal={Cell}, year={2005}, volume={123}, pages={463-475} }