Charybdotoxin, a protein inhibitor of single Ca2+-activated K+ channels from mammalian skeletal muscle

Nature. 1985 Jan 24-30;313(6000):316-8. doi: 10.1038/313316a0.


The recent development of techniques for recording currents through single ionic channels has led to the identification of a K+-specific channel that is activated by cytoplasmic Ca2+. The channel has complex properties, being activated by depolarizing voltages and having a voltage-sensitivity that is modulated by cytoplasmic Ca2+ levels. The conduction behaviour of the channel is also unusual, its high ionic selectivity being displayed simultaneously with a very high unitary conductance. Very little is known about the biochemistry of this channel, largely due to the lack of a suitable ligand for use as a biochemical probe for the channel. We describe here a protein inhibitor of single Ca2+-activated K+ channels of mammalian skeletal muscle. This inhibitor, a minor component of the venom of the Israeli scorpion, Leiurus quinquestriatus, reversibly blocks the large Ca2+-activated K+ channel in a simple biomolecular reaction. We have partially purified the active component, a basic protein of relative molecular mass (Mr) approximately 7,000.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Calcium / pharmacology*
  • Charybdotoxin
  • Chromatography
  • Electric Conductivity
  • Ion Channels / drug effects
  • Ion Channels / physiology*
  • Molecular Weight
  • Muscles / physiology*
  • Potassium / metabolism*
  • Rats
  • Scorpion Venoms / analysis
  • Scorpion Venoms / isolation & purification
  • Scorpion Venoms / pharmacology*


  • Ion Channels
  • Scorpion Venoms
  • Charybdotoxin
  • Potassium
  • Calcium