The interaction of fragment 1 of prothrombin with the membrane surface is a prerequisite for optimum expression of factor Va cofactor activity within prothrombinase.
Thromb Haemost
; 99(3): 511-22, 2008 Mar.
Article
em En
| MEDLINE
| ID: mdl-18327399
ABSTRACT
Incorporation of factor (F) Va into prothrombinase directs prothrombin activation by FXa through the meizothrombin pathway, characterized by initial cleavage at Arg(320). We have shown that a pentapeptide with the sequence DYDYQ specifically inhibits this pathway. It has been also established that Hir(54-65)(SO(3)(-)) is a specific inhibitor of prothrombinase. To understand the role of FVa within prothrombinase at the molecular level, we have studied thrombin formation by prothrombinase in the presence of various prothrombin-derived fragments alone or in combination. Activation of prethrombin 1 is slow with cleavages at Arg(320) and Arg(271) occurring with similar rates. Addition of purified fragment 1 to prethrombin 1 accelerates both the rate of cleavage at Arg(320) and thrombin formation. Both reactions were inhibited by Hir(54-65)(SO(3)(-)) while DYDYQ had no significant inhibitory effect on prethrombin 1 cleavage in the absence or presence of fragment 1. Similarly, activation of prethrombin 2 by prothrombinase, is inhibited by Hir(54-65)(SO(3)(-)), but is not affected by DYDYQ. Addition of purified fragment 1*2 to prethrombin 2 accelerates the rate of cleavage at Arg(320) by prothrombinase. This addition also results in a significant inhibition of thrombin formation by DYDYQ and is concurrent with the elimination of the inhibitory effect of Hir(54-65)(SO(3)(-)) on the same reaction. Finally, a membrane-bound ternary complex composed of prethrombin 2/fragment 1*2/Hir(54-65)(SO(3)(-)) is inhibited by DYDYQ. Altogether, the data demonstrate that membrane-bound fragment 1 is required to promote optimum Fva cofactor activity which in turn is translated by efficient initial cleavage of prothrombin by prothrombinase at Arg(320).
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Base de dados:
MEDLINE
Assunto principal:
Fragmentos de Peptídeos
/
Precursores de Proteínas
/
Fator V
/
Protrombina
/
Tromboplastina
/
Trombina
/
Fator Va
/
Fator Xa
/
Membrana Celular
/
Células Endoteliais
Tipo de estudo:
Prognostic_studies
Limite:
Humans
Idioma:
En
Revista:
Thromb Haemost
Ano de publicação:
2008
Tipo de documento:
Article
País de afiliação:
Estados Unidos