Rat Liver Prothrombin Precursors: Purification of a Second, More Basic Form

Gregory A. Grant, John W. Suttie

Research output: Contribution to journalArticlepeer-review

18 Scopus citations

Abstract

Prothrombin is produced from a microsomal precursor protein(s) by a vitamin K dependent carboxylation, which converts glutamyl residues in the precursor to 7-carboxyglutamyl residues in prothrombin. A protein with many of the properties predicted for the precursor has previously (Esmon, C. T., Grant, G. A., and Suttie, J. W. (1975), Biochemistry 14, 1595-1560) been isolated from microsomes of Warfarin-treated rats. A second protein has now been isolated from the same source. This protein has a molecular weight similar to rat prothrombin and is more basic (pI 7.2) than either rat prothrombin (pI 5.0) or the previously characterized precursor protein (pI 5.8). This protein, as does prothrombin and the other microsomal precursor, yields thrombin when treated with factor Xa and is specifically cleaved by thrombin. The rate of thrombin generation from this protein by factor Xa is not dependent on phospholipid, nor does phospholipid bind to the protein. Its rate of activation is, however, enhanced by factor V. The increased basicity of this protein is a function of an unidentified modification of the region of the protein corresponding to the Fragment-1 region of prothrombin.

Original languageEnglish
Pages (from-to)5387-5393
Number of pages7
JournalBiochemistry
Volume15
Issue number24
DOIs
StatePublished - Nov 1 1976

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