The spider toxin omega-Aga IIIA defines a high affinity site on neuronal high voltage-activated calcium channels.
J Biol Chem
; 275(28): 21309-16, 2000 Jul 14.
Article
en En
| MEDLINE
| ID: mdl-10787403
The spider toxin omega-agatoxin IIIA (omega-Aga-IIIA) is a potent inhibitor of high voltage-activated calcium currents in the mammalian brain. To establish the biochemical parameters governing its action, we radiolabeled the toxin and examined its binding to native and recombinant calcium channels. In experiments with purified rat synaptosomal membranes, both kinetic and equilibrium data demonstrate one-to-one binding of omega-Aga-IIIA to a single population of high affinity sites, with K(d) = approximately 9 pm and B(max) = approximately 1.4 pmol/mg protein. Partial inhibition of omega-Aga-IIIA binding by omega-conotoxins GVIA, MVIIA, and MVIIC identifies N and P/Q channels as components of this population. omega-Aga-IIIA binds to recombinant alpha(1B) and alpha(1E) calcium channels with a similar high affinity (K(d) = approximately 5-9 pm) in apparent one-to-one fashion. Results from recombinant alpha(1B) binding experiments demonstrate virtually identical B(max) values for omega-Aga-IIIA and omega-conotoxin MVIIA, providing further evidence for a one-to-one stoichiometry of agatoxin binding to calcium channels. The combined evidence suggests that omega-Aga-IIIA defines a unique, high affinity binding site on N-, P/Q-, and R-type calcium channels.
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Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Venenos de Araña
/
Sinaptosomas
/
Bloqueadores de los Canales de Calcio
/
Canales de Calcio Tipo N
/
Neuronas
Tipo de estudio:
Prognostic_studies
Límite:
Animals
/
Humans
Idioma:
En
Revista:
J Biol Chem
Año:
2000
Tipo del documento:
Article
País de afiliación:
Estados Unidos
Pais de publicación:
Estados Unidos