Binding properties of sea anemone toxins to sodium channels in the crayfish giant axon.
1. Effects of four different sea anemone toxins from Anthopleura (AP-A and AP-C), Anemonia (ATX II) and Parasicyonis (PaTX), and a scorpion toxin from Leiurus (LqTX) on crayfish giant axons were studied. 2. These toxins slowed the Na channel inactivation process, inducing a maintained Na current during a depolarizing pulse. 3. The binding rates for these toxins markedly decreased under depolarization. The decrease in AP-A binding was mainly derived from an increased dissociation rate under depolarization whereas that in PaTX binding from a reduced association rate. 4. The potential-dependent toxin binding kinetics seemed to be related to the gating mechanism of the Na channel. 5. Competitive bindings between these toxins were demonstrated.
D000818:Animals; D003400:Astacoidea; D001369:Axons / Q000187:drug effects*; D001665:Binding Sites / Q000187:drug effects; D001667:Binding, Competitive; D003064:Cnidarian Venoms / Q000378:metabolism / Q000633:toxicity*; D066298:In Vitro Techniques; D008433:Mathematics; D008564:Membrane Potentials / Q000187:drug effects; D012604:Scorpion Venoms / Q000494:pharmacology; D015222:Sodium Channels / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology
D003064:Cnidarian Venoms; D012604:Scorpion Venoms; D015222:Sodium Channels