Small vertical movement of a K+ channel voltage sensor measured with luminescence energy transfer

Voltage-gated ion channels open and close in response to voltage changes across electrically excitable cell membranes 1 . Voltage-gated potassium (Kv) channels are homotetramers with each subunit constructed from six transmembrane segments, S1–S6 (ref. 2 ). The voltage-sensing domain (segments S1–S4...

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Bibliographic Details
Published in:Nature (London) Vol. 436; no. 7052; pp. 848 - 851
Main Authors: Posson, David J., Ge, Pinghua, Miller, Christopher, Bezanilla, Francisco, Selvin, Paul R.
Format: Journal Article
Language:English
Published: London Nature Publishing Group UK 11.08.2005
Nature Publishing
Nature Publishing Group
Subjects:
Animals
Biological and medical sciences
Cell membranes. Ionic channels. Membrane pores
Cell structures and functions
Charged particles
Electric fields
Energy Transfer
Fundamental and applied biological sciences. Psychology
Humanities and Social Sciences
Ion Channel Gating
Ion exchange
letter
Luminescence
Luminescent Measurements
Molecular and cellular biology
Movement
multidisciplinary
Oocytes - metabolism
Potassium
Potassium - metabolism
Potassium Channels - chemistry
Potassium Channels - genetics
Potassium Channels - metabolism
Potassium Channels, Voltage-Gated - chemistry
Potassium Channels, Voltage-Gated - genetics
Potassium Channels, Voltage-Gated - metabolism
Science
Science (multidisciplinary)
Shaker Superfamily of Potassium Channels
Toxins
Xenopus laevis
Human
Luminescence
Lipids
Ionic channel
Excitable membrane
Subunit
Protein
Toxin
Electric field
Arginine
Models
Membrane channel
Potassium
ISSN:0028-0836, 1476-4687, 1476-4687
Online Access:Get full text
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Summary:Voltage-gated ion channels open and close in response to voltage changes across electrically excitable cell membranes 1 . Voltage-gated potassium (Kv) channels are homotetramers with each subunit constructed from six transmembrane segments, S1–S6 (ref. 2 ). The voltage-sensing domain (segments S1–S4) contains charged arginine residues on S4 that move across the membrane electric field 2 , 3 , modulating channel open probability. Understanding the physical movements of this voltage sensor is of fundamental importance and is the subject of controversy. Recently, the crystal structure of the KvAP 4 channel motivated an unconventional ‘paddle model’ of S4 charge movement, indicating that the segments S3b and S4 might move as a unit through the lipid bilayer with a large (15–20-Å) transmembrane displacement 5 . Here we show that the voltage-sensor segments do not undergo significant transmembrane translation. We tested the movement of these segments in functional Shaker K + channels by using luminescence resonance energy transfer to measure distances between the voltage sensors and a pore-bound scorpion toxin. Our results are consistent with a 2-Å vertical displacement of S4, not the large excursion predicted by the paddle model. This small movement supports an alternative model in which the protein shapes the electric field profile, focusing it across a narrow region of S4 (ref. 6 ).
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ISSN:0028-0836
1476-4687
1476-4687
DOI:10.1038/nature03819