title: Amphipathic antenna of an inward rectifier K+ channel responds to changes in the inner membrane leaflet.
abstract: Membrane lipids modulate the function of membrane proteins. In the case of ion channels, they bias the gating equilibrium, although the underlying mechanism has remained elusive. Here we demonstrate that the N-terminal segment (M0) of the KcsA potassium channel mediates the effect of changes in the lipid milieu on channel gating. The M0 segment is a membrane-anchored amphipathic helix, bearing positively charged residues. In asymmetric membranes, the M0 helix senses the presence of negatively charged phospholipids on the inner leaflet. Upon gating, the M0 helix revolves around the axis of the helix on the membrane surface, inducing the positively charged residues to interact with the negative head groups of the lipids so as to stabilize the open conformation (i.e., the "roll-and-stabilize model"). The M0 helix is thus a charge-sensitive "antenna," capturing temporary changes in lipid composition in the fluidic membrane. This unique type of sensory device may be shared by various types of membrane proteins.
authors.affiliation: Department of Molecular Physiology and Biophysics, Faculty of Medical Sciences,  University of Fukui, Fukui 910-1193,  Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Iwamoto
authors.forename: Shigetoshi
authors.initials: S
authors.lastname: Oiki
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D005453:Fluorescence; D006863:Hydrogen-Ion Concentration; D015640:Ion Channel Gating / Q000502:physiology*; D007700:Kinetics; D008563:Membrane Lipids / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015221:Potassium Channels / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011487:Protein Conformation; D012235:Rhodamines; D016415:Sequence Alignment
chemical_list: D001426:Bacterial Proteins; D008563:Membrane Lipids; D015221:Potassium Channels; D012235:Rhodamines; C107790:prokaryotic potassium channel; C005358:tetramethylrhodamine