The vitamin K-dependent zymogen, protein C, is synthesized in the liver as a single chain polypeptide and is subsequently converted to a disulfide linked heterodimer, by removal of a dipeptide (Lys-146 and Arg-147) from the precursor molecule (1,2). Trace quantities of the single chain form have been observed in plasma. The light chain, which is responsible for the calcium dependent binding of protein C to phospholipid vesicles, contains 11 g-carboxyglutamic acid (gla) residues, 1 b-hydroxyaspartic acid residue, and 2 epidermal growth factor (EGF) homology domains. The serine protease catalytic triad is located in the heavy chain. Human protein C is susceptible to proteolytic cleavage of a peptide (Mr=3000) from the COOH-terminal end of the heavy chain, yielding an altered form referred to as b-protein C. No functional distinction between a- and b-protein C has been observed. A single cleavage at Arg-12 (Arg-14 in bovine) of the heavy chain of human protein C converts the zymogen into the serine protease, activated protein C. This cleavage is catalyzed by a complex between a-thrombin and the endothelial cell surface protein thrombomodulin. In contrast to the other vitamin K dependent coagulation factors, activated protein C functions as an anticoagulant by catalyzing the proteolytic inactivation of factors Va and VIIIa. APC also contributes to the fibrinolytic response by complex formation with plasminogen activator inhibitors. Storage and Stability: May be stored at 4C for short-term only. For long-term storage, store at -20C. Aliquots are stable for at least 6 months at -20C. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap. Further dilutions can be made in assay buffer. Additional Specifications: Localization: Plasma Plasma Concentration: 5-10ug/ml (2) Mode of Action: Zymogen, precursor to the serine protease activated protein C (APC) Extinction Coefficient: E1%1cm, 280nm=13.7 (7) Isoelectric Point: 4.2-4.5 (8) Structure: Two chains, Mr=41,000 and 21,000, disulfide linked, NH2-terminal gla domain two EGF domains Percent Carbohydrate: 14%(7) Post-translational Modifications: Eleven gla residues, one b-hydroxyaspartate
Molecular Weight:
58000
Purity:
95% by SDS-PAGE. Bovine protein C is prepared from fresh frozen citrated plasma using a combination of immunoaffinity chromatography (5), and conventional techniques (4,9). Purity is determined by SDS-PAGE analysis and activity is measured using a chromogenic substrate based assay.
Form:
Supplied as a liquid in 50% glycerol/H2O.
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