| Research Abstract |
Isolation and Chemical Cahracterization of Two-chain Botrocetin : Two-chain Botrocetin, the von Willebrand factor (vWF) - dependent platelet coagglutinin, was purified from the venom of the snake Bothrops jararaca and characterized structurally and functionally (Biochemistry(1991)30,1957-1964). Two-chain botrocetin is a heterodimer composed of the alpha-subunit(133 amino acid residues)and the beta-subunit(125 amino acid residues)held together by a disulfide bond. In terms of amino acid sequence and disulfide bond location, it is homologous to C-type(Ca^<++> -dependent)lectins(Proc.Natl.Acad.Sci.(1993) 90,928-932). However, the activity of botrocetin in promoting vWF binding to platelets is not inhibited by EDTA or lactose and other sugars.
Out of several anti-human vWF monoclonal antibodies which inhibit ristocetin-induced platelet aggregation, only two antibodies inhibited botrocetin-induced aggregation, indicating that the binding sites on vWF of ristocetin and botrocetin are closely located but distinct (Thromb.Haemostasis(1992)68,464-469).
Structure and Function of Bothrombin : A fibrinogen clotting enzyme, termed "Bothrombin, was isolated from the venom of Bothrops jararaca and cahracterized structurally and functionally. Bothrombin is composed of a single polypeptide of 232 amino acid residues with 3 Asn-linked sugar chains. DEP totally abolished its activity, but hirudin had negligible effect on bothrmbin activity. Unlike alpha-thrombin, bothrombin split off fibrinopeptide A without releasing fibrinopeptide B.Bothrombin activated blood coagulation factor VIII, but its activity was much lower than alph-thrombin. Bothrombin did not induce platelet aggregation by itself, but did aggregate platelets in the presence of exogenous fibrinogen (Biochemistry(1994)33, 1843-1849).
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