PMID:9129813

Citation	McDonough, SI, Mintz, IM and Bean, BP (1997) Alteration of P-type calcium channel gating by the spider toxin omega-Aga-IVA. Biophys. J. 72:2117-28
Abstract	We studied the mechanism of inhibition of P-type calcium channels in rat cerebellar Purkinje neurons by the peptide toxin omega-Aga-IVA. Saturating concentrations of omega-Aga-IVA (> 50 nM) inhibited inward current carried by 2-5 mM Ba almost completely. However, outward current at depolarizations of > +60 mV, carried by internal Cs, was inhibited much less, as was the tail current after such depolarizations. omega-Aga-IVA shifted the midpoint of the tail current activation curve by about +50 mV and made the curve less steep. The inactivation curve was also shifted in the depolarized direction and was made less steep. With omega-Aga-IVA, channels activated more slowly and deactivated more quickly than in control. Trains of repeated large depolarizations relieved the inhibition of current (as tested with moderate depolarizations), probably reflecting the unbinding of toxin. The relief of inhibition was faster with increasing depolarization, but did not require internal permeant ions. We conclude that omega-Aga-IVA alters voltage-dependent gating by stabilizing closed states of the channel and that omega-Aga-IVA dissociates much more rapidly from open channels than from closed.
Links	PubMed PMC1184405 Online version:10.1016/S0006-3495(97)78854-4
Keywords	Animals; Calcium Channel Blockers/pharmacology; Calcium Channels/drug effects; Calcium Channels/metabolism; Electrophysiology; Ion Channel Gating/drug effects; Kinetics; Membrane Potentials/drug effects; Membrane Potentials/physiology; Neurons/drug effects; Rats; Spider Venoms/pharmacology; omega-Agatoxin IVA
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
AGEAP:TOG4A		GO:0019855: calcium channel inhibitor activity	ECO:0000314:		F		Fig. 1	complete CACAO 4358
AGEAP:TOG4A	enables	GO:0019855: calcium channel inhibitor activity	ECO:0000314: direct assay evidence used in manual assertion		F		Seeded From UniProt	complete

References

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