Characterization of the initial alpha-thrombin interaction with glycoprotein Ib alpha in relation to platelet activation.
J Biol Chem
; 273(4): 1880-7, 1998 Jan 23.
Article
em En
| MEDLINE
| ID: mdl-9442020
ABSTRACT
We have evaluated the properties of alpha-thrombin interaction with platelets within 1 min from exposure to the agonist, a time frame during which most induced activation responses are initiated and completed. Binding at 37 degrees C was rapidly reversible and completely blocked by a monoclonal antibody, LJ-Ib10, previously shown to be directed against the alpha-thrombin interaction site on glycoprotein (GP) Ib alpha. By 2-5 min, however, binding was no longer fully reversible and was only partially inhibited by the anti-GP Ib alpha antibody. Results were similar at room temperature (22-25 degrees C), whereas the initial characteristics of alpha-thrombin interaction with platelets were preserved for at least 20 min at 4 degrees C. Equilibrium binding isotherms obtained at the latter temperature were compatible with a two-site model, but the component ascribed to GP Ib alpha, completely inhibited by LJ-Ib10, had "moderate" affinity (kd on the order of 10(-8) M) and relatively high capacity, rather than "high" affinity (kd on the order of 10(-10) M) and low capacity as currently thought. The parameters of alpha-thrombin binding to intact GP Ib alpha on platelets at 4 degrees C corresponded closely to those measured with isolated GP Ib alpha fragments regardless of temperature. Blocking the alpha-thrombin-GP Ib alpha interaction caused partial inhibition of ATP release and prevented the association with platelets of measurable proteolytic activity. These results support the concept that GP Ib alpha contributes to the thrombogenic potential of alpha-thrombin.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Trombina
/
Ativação Plaquetária
/
Complexo Glicoproteico GPIb-IX de Plaquetas
Tipo de estudo:
Prognostic_studies
Limite:
Humans
Idioma:
En
Revista:
J Biol Chem
Ano de publicação:
1998
Tipo de documento:
Article