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Triton-insoluble cytoskeletons prepared from thrombin-activated platelets were found to potentiate the activation of prothrombin (prothrombinase activity). Cytoskeletons prepared from red cells or lymphoblasts contained no prothrombinase activity. The platelet prothrombinase activity was dependent on cytoskeletal-associated Factor Va, and exogenously added Factor Xa and prothrombin. Cytoskeletons contained 38% of the total platelet prothrombinase activity. Both platelets and cytoskeletons displayed half-maximal activities at similar prothrombin concentrations. The role of lipids in the cytoskeletal prothrombinase activity was investigated. Cytoskeletons were found to contain 3.8% of the total platelet phospholipids, consisting of the following lipids expressed as percentage of total present in platelets: 6.0% sphingomyelin, 3.8% phosphatidylcholine, 2.9% phosphatidyl-ethanolamine, 4.4% phosphatidylinositol, and 2.2% phosphatidylserine. The cytoskeletal prothrombinase activity and the lipid phosphorus content of cytoskeletons decreased after treatment of cytoskeletons with various doses of phospholipase C. Incubation of cytoskeletons with the highest concentrations tested (10 micrograms/ml) resulted in a 72% loss of phosphatidylserine and 84% loss of cytoskeletal prothrombinase activity. Cytoskeletal prothrombinase activity destroyed by phospholipase C treatment could be restored to control levels by treatment of hydrolyzed cytoskeletons with total cytoskeletal lipid or mixtures of phosphatidylserine/phosphatidylcholine (25:75% by weight). These results suggest that the cytoskeletal prothrombinase complex in addition to containing Factor Va, as has been previously shown (15), contains a lipid cofactor activity consisting in part of phosphatidylserine.
G P Tuszynski, and
G P Mauco, and
A Koshy, and
P K Schick, and
P N Walsh
January 1986,
The Biochemical journal,
G P Tuszynski, and
G P Mauco, and
A Koshy, and
P K Schick, and
P N Walsh
January 1985,
Nouvelle revue francaise d'hematologie,
G P Tuszynski, and
G P Mauco, and
A Koshy, and
P K Schick, and
P N Walsh
January 1982,
Biophysical journal,
G P Tuszynski, and
G P Mauco, and
A Koshy, and
P K Schick, and
P N Walsh
January 1993,
Methods in enzymology,
G P Tuszynski, and
G P Mauco, and
A Koshy, and
P K Schick, and
P N Walsh
March 1993,
Blood,
G P Tuszynski, and
G P Mauco, and
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P N Walsh
January 1984,
Haemostasis,
G P Tuszynski, and
G P Mauco, and
A Koshy, and
P K Schick, and
P N Walsh
January 1997,
Journal of thrombosis and thrombolysis,
G P Tuszynski, and
G P Mauco, and
A Koshy, and
P K Schick, and
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April 2015,
The Biochemical journal,
G P Tuszynski, and
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June 1990,
Blood coagulation & fibrinolysis : an international journal in haemostasis and thrombosis,
G P Tuszynski, and
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December 1993,
Thrombosis and haemostasis,
