Interactions between dendrotoxin, a blocker of voltage-dependent potassium channels, and charybdotoxin, a blocker of calcium-activated potassium channels, at binding sites on neuronal membranes.
Dendrotoxin I (DpI) from black mamba venom (Dendroaspis polylepis) has high affinity binding sites on rat brain synaptic membranes. Native DpI displaced [125I]-DpI binding with a Ki of 1 x 10(-10) M, and over 90% of specific binding was displaceable. Charybdotoxin isolated from the Israeli scorpion venom (Leiurus quinquestriatus hebraeus), also displaced [125I]-DpI binding, with a Ki of approximately 3 x 10(-9) M, although the displacement curve was shallower than with native DpI. Both toxins are thought to be high affinity blockers of specific K+ currents. Charybdotoxin selectively blocks some types of Ca2+-activated K+ channels, whereas dendrotoxins only block certain voltage-dependent K+ channels. The interaction between the two types of toxin at the DpI binding site is unexpected and may suggest the presence of related binding sites on different K+ channel proteins.
Harvey
A L
AL
Department of Physiology and Pharmacology, University of Strathclyde, Glasgow, U.K.
Marshall
D L
DL
De-Allie
F A
FA
Strong
P N
PN
D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D001921:Brain / Q000378:metabolism*; D002118:Calcium / Q000502:physiology; D018999:Charybdotoxin; D004546:Elapid Venoms / Q000378:metabolism*; D008564:Membrane Potentials; D009498:Neurotoxins / Q000378:metabolism*; D015221:Potassium Channels / Q000378:metabolism*; D051381:Rats; D012604:Scorpion Venoms / Q000494:pharmacology*; D013574:Synaptosomes
D004546:Elapid Venoms; D009498:Neurotoxins; D015221:Potassium Channels; D012604:Scorpion Venoms; D018999:Charybdotoxin; C020273:dendrotoxin; D002118:Calcium