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Updated: Jul 1, 2026

Use of Label-free Optical Biosensors to Detect Modulation of Potassium Channels by G-protein Coupled Receptors
Published on: February 10, 2014
Large-scale movement within the voltage-sensor paddle of a potassium channel-support for a helical-screw motion
Amir Broomand1, Fredrik Elinder
1Department of Clinical and Experimental Medicine, Division of Cell Biology, Linköping University, SE-58185 Linköping, Sweden.
Abstract:
The size of the movement and the molecular identity of the moving parts of the voltage sensor of a voltage-gated ion channel are debated. In the helical-screw model, the positively charged fourth transmembrane segment S4 slides and rotates along negative counter charges in S2 and S3, while in the paddle model, S4 carries the extracellular part of S3 (S3b) as a cargo. Here, we show that S4 slides 16-26 A along S3b. We introduced pairs of cysteines in S4 and S3b of the Shaker K channel to make disulfide bonds. Residue 325 in S3b makes close and state-dependent contacts with a long stretch of residues in S4. A disulfide bond between 325 and 360 was formed in the closed state, while a bond between 325 and 366 was formed in the open state. These data are not compatible with the voltage-sensor paddle model, but support the helical-screw model.
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