The protein component of human brain thromboplastin

The protein component of human brain tissue thromboplastin (factor III) has been purified by deoxycholate (DOC) extraction, ultracentrifugation, gel filtration and finally repeated preparative polyacrylamide gel electrophoresis (PGE) in the presence of sodium dodecylsulphate (SDS). The final preparations gave one band in analytical PGE. Reduced and alkylated protein appeared as a band of molecular weight about 53 000 in SDS-PGE.The protein had a low solubility in aqueous solutions in the absence of detergents. When recombined with an optimal amount of the phospholipid fraction of tissue thromboplastin (fraction B) the procoagulant thromboplastin activity was regained. Neither alone nor after recombination with phospholipid did the protein catalyze the hydrolysis of aminoacyl-β-naphthylamides or casein.