Voltage-dependent dynamics of the BK channel cytosolic gating ring are coupled to the membrane-embedded voltage sensor

Elife. 2018 Dec 11;7:e40664. doi: 10.7554/eLife.40664.

Abstract

In humans, large conductance voltage- and calcium-dependent potassium (BK) channels are regulated allosterically by transmembrane voltage and intracellular Ca2+. Divalent cation binding sites reside within the gating ring formed by two Regulator of Conductance of Potassium (RCK) domains per subunit. Using patch-clamp fluorometry, we show that Ca2+ binding to the RCK1 domain triggers gating ring rearrangements that depend on transmembrane voltage. Because the gating ring is outside the electric field, this voltage sensitivity must originate from coupling to the voltage-dependent channel opening, the voltage sensor or both. Here we demonstrate that alterations of the voltage sensor, either by mutagenesis or regulation by auxiliary subunits, are paralleled by changes in the voltage dependence of the gating ring movements, whereas modifications of the relative open probability are not. These results strongly suggest that conformational changes of RCK1 domains are specifically coupled to the voltage sensor function during allosteric modulation of BK channels.

Keywords: BK; allosteric modulation; human; ion channels; molecular biophysics; structural biology; xenopus.

Publication types

  • Research Support, N.I.H., Intramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Allosteric Regulation
  • Animals
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Binding Sites
  • Calcium / metabolism*
  • Cell Membrane / metabolism*
  • Cytosol / metabolism
  • Fluorescence Resonance Energy Transfer
  • Gene Expression
  • Genes, Reporter
  • Green Fluorescent Proteins / genetics
  • Green Fluorescent Proteins / metabolism
  • Humans
  • Ion Channel Gating / physiology
  • Large-Conductance Calcium-Activated Potassium Channels / genetics
  • Large-Conductance Calcium-Activated Potassium Channels / metabolism*
  • Luminescent Proteins / genetics
  • Luminescent Proteins / metabolism
  • Membrane Potentials / physiology*
  • Mutation
  • Oocytes / cytology
  • Oocytes / metabolism
  • Patch-Clamp Techniques
  • Plasmids / chemistry
  • Plasmids / metabolism
  • Potassium / metabolism*
  • Protein Binding
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Xenopus laevis

Substances

  • Bacterial Proteins
  • Cyan Fluorescent Protein
  • Large-Conductance Calcium-Activated Potassium Channels
  • Luminescent Proteins
  • Recombinant Proteins
  • yellow fluorescent protein, Bacteria
  • Green Fluorescent Proteins
  • Potassium
  • Calcium