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 |
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Authors: | A L Harvey D L Marshall F A De-Allie P N Strong |
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Affiliation: | Department of Physiology and Pharmacology, University of Strathclyde, Glasgow, U.K. |
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Abstract: | 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. |
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