Dissociation and association of the oligomeric forms of factor V

Rat coagulation factor V purification and production of the monospecific antiserum

An original method was applied to purify rat factor V. The final preparation had a sp. act. of 45 U/ml for a 2500-fold purification with a yield of 43%. The final product is partially activated since it is 4.7-fold activable by RVV-VAE vs 6.3 in plasma. It can explain the presence of some of the four slightly stained additional bands found in SDS-electrophoresis. Finally, results of the purification suggest that rat factor V is a 338,000 single chain glycoprotein with a strong molecular asymmetry. A factor V deficient fraction was produced and used to adsorb an anti-factor V antiserum. This adsorbed antiserum was found monospecific against purified rat factor V.

Isolation and partial characterization of human factor V

Factor V was isolated from human citrate plasma by very mild purification steps. Cryoprecipitation, fractionation with polyethylene glycol 6000, gel filtration of AcA 44 and adsorption of haptoglobin to immobilized hemoglobin were applied successively, resulting in factor V preparations with a specific activity of 14.5 unit/mg. The yield was 28 percent. A molecular weight of 296 000 was determined by gel filtration and the apparent sedimentation constant found by ultracentrifugation in a sucrose gradient was 7.8 S. Parallel experiments with citrate plasma resulted in the same molecular weight and sedimentation constant. Polyacrylamide gel electrophoresis of factor V in the presence or absence of sodium dodecyl sulfate showed a single protein band. Incubation with human thrombin resulted in an 8-fold activation of the purified factor V.

Molecular changes associated with proteolysis of bovine factor V by thrombin

Native factor V contains two major polypeptide chains, h and 1. The molecular weights determined by gel electrophoresis in the presence of sodium dodecylsulfate and dithiothreitol (125 000 and 73 000) are in reasonable agreement with those obtained by gel filtration in 5 M guanidine-HC1 (125000 and 64000). Exposure of factor V to thrombin results in cleavage of the heavier chain to an altered form with a molecular weight of 87000. The other fragment of this proteolytic reaction appears to be a carbohydrate-rich piece, which migrates abnormally slowly on gel electrophoresis conducted under denaturing and reducing conditions. Both proteolytic cleavage products remain associated with the light chain during the purification of factor V. The 87000-Mr fragment is present in samples of factor V which are isolated by immunoprecipitation of blood obtained from a single animal by venous catheter. This finding suggests that some proteolysis may occur in vivo. In contrast, the molecular weight of the light chain is unaltered after thrombin proteolysis of either purified factor V or thrombin-treated plasma.

Immunochemical studies on factor V

Native bovine factor V exhibits a molecular weight of 300000 as determined by gel filtration of untreated plasma. Highly purified factor V exhibits multiple molecular weight forms which range from small active fragments to aggregates of several million which are generated during the purification on cellulose phosphate. Isoelectric focusing on a single high-molecular-weight species produced a single protein and activity peak at pH 4.65. Factor V activity is associated with each protein band observed following polyacrylamide gel electrophoresis. Antisera to factor V prepared in rabbits produces a time-dependent and concentration-dependent inhibition of factor V activity in plasma and purified factor V. The multiple molecular weight forms of factor V appear equivalent upon immunodiffusion and on immunoelectrophoresis migrate as an alpha globulin between albumin and fibrinogen. Immunoprecipitation arcs are equivalent in plasma and serum. Factor V consists of two major types of subunits, a light chain (73000), aggregates of which form the high-molecular-weight species, and a heavy chain (125 000). Using preparations containing one or both chains isolated by disc gel electrophoresis, antiserum was shown to contain two families of antibodies, one against each subunit. Cross reactivity with both light and heavy chain antigens is observed in sheep and goat but not monkey or human plasma. The antisera also neutralized goat and sheep factor V activity.

The preparation and properties of factor V from bovine plasma

1. A procedure for the purification of factor V from bovine plasma with a good yield and in a high state of purity is described. The isolation procedure involves BaSO4, adsorption, chromatography of the absorbed plasma on DEAE-Sephadex A-50, activation with thrombin of the A-50 eluate, chromatography on Amberlite CG-50 and precipitation with (NH4)2SO4. Factor V is obtained with a 160% yield and 5000-fold purification. 2. Some of the physico-chemical properties of Ac-globulin have been measured. The molecular weight was determined by electrophoresis is SDS-polyacrylamide gel and found to be 30 000. The studies employing disc electrophoresis and immunoelectrophoresis suggest the existence of several active isoforms of factor V.

The disociation of bovine factor V and isolation of the acitivated form

Bovine Factor V disociated non-enzymatically to 276 000 dalton, whereas, the enzymatic activation produced Factor Va of 213 500 daltons. The disociated form, Factor Vd, was not an enzyme substrate for conversion to Factor Va. Factors V and Va sedimented in a density zone of 1.19 g/ml, and Factor Vd in 1.17 g/ml, in sucrose gradient centrifugation. Only a neutral lipid in a 7.2% yield could be extracted from Factor Va which had been isolated in a 4500-fold purification.