Charybdotoxin, a protein inhibitor of single Ca2+-activated K+ channels from mammalian skeletal muscle.
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.
Miller
C
C
Moczydlowski
E
E
Latorre
R
R
Phillips
M
M
D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D018999:Charybdotoxin; D002845:Chromatography; D004553:Electric Conductivity; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D008970:Molecular Weight; D009132:Muscles / Q000502:physiology*; D011188:Potassium / Q000378:metabolism*; D051381:Rats; D012604:Scorpion Venoms / Q000032:analysis / Q000302:isolation & purification / Q000494:pharmacology*
D007473:Ion Channels; D012604:Scorpion Venoms; D018999:Charybdotoxin; D011188:Potassium; D002118:Calcium