Purified prothrombin can be converted into thrombin in different ways (2), namely, by the use of biological activators, by the action of high concentrations of sodium citrate, and by treatment with trypsin. Biological activation of prothrombin requires lipoprotein tissue-factor(s) that have prothrombin-converting or thromboplastic activity, protein serum-factor(s) which augment thromboplastic a...

We present functional and binding data relevant to the reported roles for prothrombin and beta 2-glycoprotein I (beta 2GPI) in the expression of lupus anticoagulant activity. In a purified system containing human prothrombin, Xa, Va, and a rate-limiting concentration of phosphatidylserine (PS)/phosphatidylcholine (PC) vesicles, the preliminary incubation of vesicles with protein A separated IgG...

The G20210A polymorphism has been shown to alter the efficiency of prothrombin mRNA processing. Here we show that the G20210A mutation also alters prothrombin mRNA stability. Three-fold more prothrombin protein and mRNA were produced in NIH-3T3 cells transfected with the prothrombin cDNAs containing the 20210A variant compared to cells expressing the 20210G variant. mRNA stability assays using ...

An active site mutant bovine prothrombin cDNA (Ser528----Ala) has been constructed, subcloned, and expressed in Chinese hamster ovary cells. The recombinant mutant prothrombin, expressed at the level of 1.5-2.0 micrograms/ml of cell medium, was fully carboxylated (9.9 +/- 0.4 mol of gamma-carboxyglutamic acid/mol of prothrombin). The mutant prothrombin could be activated to thrombin by Taipan s...

A dysprothrombin designated prothrombin Segovia was isolated from the plasma of an individual with normal prothrombin antigen and prothrombin activity lesser than 25% of the control prothrombin activity. Activation by prothrombinase complex showed a lower amidolytic than clotting activity, which suggests a lesser generation of active intermediates than normal prothrombin. When prothrombin Segov...

Protein S is a vitamin K-dependent nonenzymatic coagulation factor involved in the regulation of activated protein C (aPC). In this study, we report an aPC-independent anticoagulant function of protein S in plasma under flow conditions. Plasma, anticoagulated with low-molecular-weight heparin allowing tissue factor-dependent prothrombin activation, was perfused at a wall shear rate of 100 s-1 o...

Recent studies' have established the presence of a factor ("activator," Coagulase-reacting factor, or CRF) in plasma which is required for the coagulation of blood by staphylocoagulase. Maximum CRF activity resides in the globulin fractions of plasma, and separation from prothrombin is best achieved by repeated Seitz filtration.10 The filtration involves different rates of adsorption of prothro...

During the process of normal blood coagulation prothrombin is converted into thrombin. As a result serum contains considerably less prothrombin than the plasma from which it is derived, the prothrombin having been consumed during the coagulation of the blood. In certain conditions this conversion is incomplete and much prothrombin remains in the serum. Often this is not obvious from the usual t...

We have discovered that addition of monomeric desAB fibrin to prothrombin leads to appearance of the thrombin-like activity of prothrombin towards S2238 chromogenic substrate. DesA and desABβ(15-42)2 fibrin forms did not cause any activation of prothrombin. From this observation we could suggested that amino acid residues of the 15-42 fragment of BβN-domain presented in desAB fibrin, cleaved in...

W ITH increasing use of tests of the prothrombin concentration as an aid in the diagnosis of diseases of the liver and as a guide in vitamin K and dicumarol therapy,’6 it is imperative that the determinations be accurate. There are many ways of measuring the prothrombin concentration and each admits of numerous sources of error. Even when the most careful technic is practiced, appreciable error...