Transmembrane movement of the Shaker K super(+) channel S4

We have probed internal and external accessibility of S4 residues to the membrane-impermeant thiol reagent methanethiosulfonate-ethyltrimethylammonium (MTSET) in both open and closed, cysteine-substituted Shaker K super(+) channels. Our results indicate that S4 traverses the membrane with no more th...

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Bibliographic Details
Published in:Neuron (Cambridge, Mass.) Mass.), 1996-01, Vol.16 (2), p.387-397
Main Authors: Larsson, H P, Baker, O S, Dhillon, D S, Isacoff, E Y
Format: Article
Language:English
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Summary:We have probed internal and external accessibility of S4 residues to the membrane-impermeant thiol reagent methanethiosulfonate-ethyltrimethylammonium (MTSET) in both open and closed, cysteine-substituted Shaker K super(+) channels. Our results indicate that S4 traverses the membrane with no more than 5 amino acids in the closed state, and that the distribution of buried residues changes when channels open. This change argues for a displacement of S4 through the plane of the membrane in which an initially intracellular residue moves to within 3 amino acids of the extracellular solution. These results demonstrate that the putative voltage-sensing charges of S4 actually reside in the membrane and that they move outward when channels open. We consider constraints placed on channel structure by these results.
ISSN:0896-6273