Protein S (PROS1, PROS, Vitamin K dependent protein S)

Protein S is a vitamin K-dependent, potent neutral anticoagulant plasma glycoprotein. Protein S has a molecular weight of approximately 70kD and concists of a single polypeptide chain. The concentration of protein S in human plasma is 25ug/ml, with a half-life of approximately two days. About 40% of Protein S in plasma is in a free form, whereas 60% is complexed with C4b-binding Protein (C4BP). Only the free Protein S functions as a cofactor to antigen presenting cells (APC) in the APC-dependent degradation of Factor Va and Factor VIIIa.\n\nProtein S is thought to function in both the coagulation and complement cascades. It has been suggested that g-carboxyglutamic acid (gla) dependent binding of protein S to negatively charged phospholipids may function to concentrate C4BP at cell surfaces following injury. \n\nIn the coagulation system, Protein S functions as an anticoagulant cofactor protein. Activated Protein C (APC) forms a 1:1 stoichiometric complex with Protein S in the presence of Ca2+ and phospholipid vesicles (Kd=6x10e-9M). In the presence of Protein S, a moderate increase (3-10 fold) in the rate of factor Va and factor VIIIa inactivation by APC is observed in plasma and on the surface of unstimulated platelets. Protein S bound to C4BP does not possess APC cofactor activity. Recently, an additional binding protein which enhances the activity of Protein S has been described. Proteolytic inactivation of Protein S by thrombin has been proposed as a regulatory mechanism in this system. A single cleavage by thrombin abolishes Protein S cofactor activity by removing an NH2-terminal peptide (Mr=8000) which contains the gla domain. \n\nThe domain structure of Protein S is similar to that of the other vitamin K-dependent coagulation factors with the exception that Protein S does not possess the catalytic triad. Protein S is a single chain protein containing 10 gla residues in the NH2-terminal domain and 4 epidermal growth factor (EGF) domains.\n\nApplications: \nSuitable for use in Western Blot and RIEP (Radioimmunoelectrophoresis). Other applications not tested.\n\nRecommended Dilution:\nWestern Blot: 10ug/ml\nOptimal dilutions to be determined by the researcher.\n\nExtinction Coefficient:\nE1%, 1cm, 280nm = 14.0\n\nMolecular Weight:\n150kD\n\nStorage and Stability:\nMay be stored at 4 degrees C for short-term only. For long-term storage, store at -20 degrees C. Aliquots are stable for at least 12 months at -20 degrees C. 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.

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