Technical Data
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.

Protein 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.

In 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.

The 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.

Suitable for use in Western Blot and RIEP (Radioimmunoelectrophoresis). Other applications not tested.

Recommended Dilution:
Western Blot: 10ug/ml
Optimal dilutions to be determined by the researcher.

Extinction Coefficient:
E1%, 1cm, 280nm = 14.0

Molecular Weight:

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 12 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.
PabIgGHighly Purified
100ug4C (-20C Glycerol)Blue IceHumanGoat
Human Protein S
~ 95%. Purified by ammonium sulfate precipitation followed by Ion Exchange chromatography.
Supplied as a liquid in HEPES buffered saline, pH 7.4, 50% glycerol.
Recognizes human Protein S.
Intended for research use only. Not for use in human, therapeutic, or diagnostic applications.
1. Law SKA, Reid KBM (1988) Complement. In: In Focus (Ed. Male D) IRL Press: Oxford.
2. Bendtzen K et al (2000) Basal og klinisk immunologi. FADLs Forlag A/S, Copenhagen.