Cooperative activation of action potential Na+ ionophore by neurotoxins.

Four neurotoxins that activate the action potential Na+ ionophore of electrically excitable neuroblastoma cells interact with two distinct classes of sites, one specific for the alkaloids veratridine, batrachotoxin, and aconitine, and the second specific for scorpion toxin. Positive heterotropic cooperativity is observed between toxins bound at these two classes of sites. Tetrodotoxin is a nonc...

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Cooperative Activation of Action Potential Na+ lonophore by Neurotoxins

Four neurotoxins that activate the action potential Na+ ionophore of electrically excitable neuroblastoma cells interact with two distinct classes of sites, one specific for the alkaloids veratridine, batrachotoxin, and aconitine, and the second specific for scorpion toxin. Positive heterotropic cooperativity is observed between toxins bound at these two classes of sites. Tetrodotoxin is a nonc...

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Activation of the action potential Na+ ionophore by neurotoxins. An allosteric model.

The alkaloid neurotoxins aconitine, veratridine, grayanotoxin, and batrachotoxin activate the action potential Na+ ionophore by interaction with a common binding site. Concentration-response curves are fit by simple Langmuir isotherms. The fraction of Na+ ionophores activated at saturating concentrations of neurotoxin are: aconitine, 0.02; veratridine, 0.08; grayanotoxin, 0.51; and batrachotoxi...

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Cooperative Activation of Action Potential Na+ lonophore by Neurotoxins (neuroblastoma cells/passive 22Na+ influx/batrachotoxin/veratridine/aconitine/scorpion toxin)

Four neurotoxins that activate the action potential Na+ ionophore of electrically excitable neuroblastoma cells interact with two distinct classes of sites, one specific for the alkaloids veratridine, batrachotoxin, and aconitine, and the second specific for scorpion toxin. Positive heterotropic cooperativity is observed between toxins bound at these two classes of sites. Tetrodotoxin is a nonc...

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Membrane potential dependent binding of scorpion toxin to action potential Na+ ionophore.

Depolarization of neuroblastoma cells causes a 70-fold increase in the apparent dissociation constant KD for scorpion toxin enhancement of activation of the action potential Na+ ionophore by veratridine and a large increase in the rate of reversal of scorpion toxin action. Depolarization also inhibits binding of 125I-labeled scorpion toxin to a small number of saturable binding sites on electri...

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Cooperative activation of action potential Na+ ionophore by neurotoxins.

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