Control of inward rectifier K channel activity by lipid tethering of cytoplasmic domains

J Gen Physiol. 2007 Sep;130(3):329-34. doi: 10.1085/jgp.200709764. Epub 2007 Aug 13.

Abstract

Interactions between nontransmembrane domains and the lipid membrane are proposed to modulate activity of many ion channels. In Kir channels, the so-called "slide-helix" is proposed to interact with the lipid headgroups and control channel gating. We examined this possibility directly in a cell-free system consisting of KirBac1.1 reconstituted into pure lipid vesicles. Cysteine substitution of positively charged slide-helix residues (R49C and K57C) leads to loss of channel activity that is rescued by in situ restoration of charge following modification by MTSET(+) or MTSEA(+), but not MTSES(-) or neutral MMTS. Strikingly, activity is also rescued by modification with long-chain alkyl-MTS reagents. Such reagents are expected to partition into, and hence tether the side chain to, the membrane. Systematic scanning reveals additional slide-helix residues that are activated or inhibited following alkyl-MTS modification. A pattern emerges whereby lipid tethering of the N terminus, or C terminus, of the slide-helix, respectively inhibits, or activates, channel activity. This study establishes a critical role of the slide-helix in Kir channel gating, and directly demonstrates that physical interaction of soluble domains with the membrane can control ion channel activity.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Bacterial Proteins / chemistry
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Burkholderia pseudomallei / genetics
  • Burkholderia pseudomallei / metabolism*
  • Cell-Free System
  • Cloning, Molecular
  • Cysteine
  • Ethyl Methanesulfonate / analogs & derivatives
  • Ethyl Methanesulfonate / chemistry
  • Ion Channel Gating*
  • Membrane Lipids / metabolism*
  • Mesylates / chemistry
  • Methyl Methanesulfonate / analogs & derivatives
  • Methyl Methanesulfonate / chemistry
  • Models, Molecular
  • Mutation
  • Potassium Channels, Inwardly Rectifying / chemistry
  • Potassium Channels, Inwardly Rectifying / genetics
  • Potassium Channels, Inwardly Rectifying / metabolism*
  • Protein Binding
  • Protein Conformation
  • Protein Structure, Tertiary
  • Rubidium Radioisotopes
  • Sulfhydryl Reagents / chemistry

Substances

  • Bacterial Proteins
  • Membrane Lipids
  • Mesylates
  • Potassium Channels, Inwardly Rectifying
  • Rubidium Radioisotopes
  • Sulfhydryl Reagents
  • methanethiosulfonate ethylammonium
  • (2-sulfonatoethyl)methanethiosulfonate
  • (2-(trimethylammonium)ethyl)methanethiosulfonate
  • methyl methanethiosulfonate
  • Ethyl Methanesulfonate
  • Methyl Methanesulfonate
  • Cysteine