Membrane insertion of a potassium-channel voltage sensor.
The mechanism of voltage gating in K+ channels is controversial. The paddle model posits that highly charged voltage-sensor domains move relatively freely across the lipid bilayer in response to membrane depolarization; competing models picture the charged S4 voltage-sensor helix as being shielded from lipid contact by other parts of the protein. We measured the apparent free energy of membrane insertion of a K+-channel S4 helix into the endoplasmic reticulum membrane and conclude that S4 is poised very near the threshold of efficient bilayer insertion. Our results suggest that the paddle model is not inconsistent with the high charge content of S4.
Hessa
Tara
T
Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden.
White
Stephen H
SH
von Heijne
Gunnar
G
D001120:Arginine / Q000032:analysis / Q000737:chemistry; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000737:chemistry / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism; D006031:Glycosylation; D057927:Hydrophobic and Hydrophilic Interactions; D007425:Intracellular Membranes / Q000737:chemistry / Q000378:metabolism*; D008051:Lipid Bilayers; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D008954:Models, Biological; D010957:Plasmids; D024642:Potassium Channels, Voltage-Gated / Q000737:chemistry* / Q000378:metabolism*; D017433:Protein Structure, Secondary; D013816:Thermodynamics
D029968:Escherichia coli Proteins; D008051:Lipid Bilayers; D008565:Membrane Proteins; D024642:Potassium Channels, Voltage-Gated; D001120:Arginine