Transmembrane movement of the shaker K+ channel S4.
We have probed internal and external accessibility of S4 residues to the membrane-impermeant thiol reagent methanethiosulfonate-ethyltrimethlammonium (MTSET) in both open and closed, cysteine-substituted Shaker K+ 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.
Larsson
H P
HP
Department of Molecular and Cell Biology, University of California, Berkeley 94720, USA.
Baker
O S
OS
Dhillon
D S
DS
Isacoff
E Y
EY
D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D004330:Drosophila / Q000235:genetics*; D009154:Mutation; D009865:Oocytes / Q000378:metabolism; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000187:drug effects / Q000235:genetics* / Q000502:physiology*; D013439:Sulfhydryl Reagents / Q000494:pharmacology; D014982:Xenopus laevis
D015221:Potassium Channels; D013439:Sulfhydryl Reagents