Human activated protein C
[PROC_HUMAN] Defects in PROC are the cause of thrombophilia due to protein C deficiency, autosomal dominant (THPH3) [MIM:176860]. A hemostatic disorder characterized by impaired regulation of blood coagulation and a tendency to recurrent venous thrombosis. However, many adults with heterozygous disease may be asymptomatic. Individuals with decreased amounts of protein C are classically referred to as having type I protein C deficiency and those with normal amounts of a functionally defective protein as having type II deficiency.              Defects in PROC are the cause of thrombophilia due to protein C deficiency, autosomal recessive (THPH4) [MIM:612304]. A hemostatic disorder characterized by impaired regulation of blood coagulation and a tendency to recurrent venous thrombosis. It results in a thrombotic condition that can manifest as a severe neonatal disorder or as a milder disorder with late-onset thrombophilia. The severe form leads to neonatal death through massive neonatal venous thrombosis. Often associated with ecchymotic skin lesions which can turn necrotic called purpura fulminans, this disorder is very rare.
[PROC_HUMAN] Protein C is a vitamin K-dependent serine protease that regulates blood coagulation by inactivating factors Va and VIIIa in the presence of calcium ions and phospholipids.
Publication Abstract from PubMed
The structure of the Gla-domainless form of the human anticoagulant enzyme activated protein C has been solved at 2.8 A resolution. The light chain is composed of two domains: an epidermal growth factor (EGF)-like domain modified by a large insert containing an additional disulfide, followed by a typical EGF-like domain. The arrangement of the long axis of these domains describes an angle of approximately 80 degrees. Disulfide linked to the light chain is the catalytic domain, which is generally trypsin-like but contains a large insertion loop at the edge of the active site, a third helical segment, a prominent cationic patch analogous to the anion binding exosite I of thrombin and a trypsin-like Ca[II] binding site. The arrangement of loops around the active site partially restricts access to the cleft. The S2 and S4 subsites are much more polar than in factor Xa and thrombin, and the S2 site is unrestricted. While quite open and exposed, the active site contains a prominent groove, the surface of which is very polar with evidence for binding sites on the primed side, in addition to those typical of the trypsin class found on the non-primed side.
The 2.8 A crystal structure of Gla-domainless activated protein C.,Mather T, Oganessyan V, Hof P, Huber R, Foundling S, Esmon C, Bode W EMBO J. 1996 Dec 16;15(24):6822-31. PMID:9003757
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.