Vitronectin is a plasma glycoprotein that circulates in the blood at a concentration range of 200 to 400mg/ml constituting 0.2 to 0.5% of total plasma proteins (1,2). It is detected as a mixture of both 75kDa and 65kDa forms (3). The 65kDa form is a product of proteolytic processing of the former which appears to be endogenously present. Vitronectin is involved in a number of physiological processes that include blood coagulation, fibrinolysis, complement cascade, and cell adhesion. Vitronectin (Serum spreading factor) is one of the two major cell-adhesive glycoproteins. It is a major ligand for the vitronectin receptor (aV/b3) or aV/b5 integrin on adhesive cells (4). Other functions include heparin-binding, collagen-binding, osteonectin-binding, complement lysis inhibitor and ''scavenger protein for macromolecular products of the complement and haemostasis cascade systems (5). It also functions as a substrate for trans glutaminase (Factor XIIIa) crosslinking, cAMP-dependent protein kinase, and tyrosyl protein sulfotransferase (4,5). Vitronectin has implications for thrombosis due to its heparin binding properties. It has been postulated that vitronectin prevents the acceleration of clot formation inhibition by acting as a heparin scavenger ultimately protecting thrombin and factor Xa from heparin-dependent inactivation by antithrombin III or heparin cofactor II (6,7). Vitronectin is also thought to play an important role in fibrinolysis by its ability to bind active PAI-1 (4). Extracellular binding of vitronectin to plasminogen activator inhibitor-1 (PAI-1) and plasminogen, stabilize the inhibitor and thus affect tissue plasminogen activator-mediated plasmin formation (4). The vitronectin domain structure starting at the NH4-terminus consists of a somatomedin-B region (residues 1 to 44), a connecting segment containing the major cell attachment RGD sequence (residues 45 to 47) and a highly acidic region (residues 53 to 64), followed by hemopexin-like repeats (homology to hemopexin which is a heme-binding plasma protein), a glycosaminoglycan-binding site which is represented by a 40-amino acid stretch rich in basic residues, a protease-sensitive region susceptible to high concentrations of thrombin, and a COOH-terminal protein kinase A-dependent phosphorylation site, which is adjacent to the protease cleavage site (4,5). Vitronectin provides a molecular link important for cell adhesion and regulation of defense mechanisms in the terminal steps of blood coagulation and complement cascades Plasma Concentration: 200-400mg/ml Molecular Weight: 75,000 single-chain form and a two-chain form composed of 10,000 and 65,000 (SDS-PAGE) (4) Extinction Coefficient: E1%1cm, 280nm=13.8 Isoelectric Point: 4.75-5.25 (8M urea) Structure: Circulates in monomeric, dimeric and possibly higher oligomeric forms. Monomer: 459aa, single chain polypeptide with seven intrachain disulfides and one free sulfhydryl. Percent Carbohydrate: 10-15% Storage and Stability: Aliquot to avoid repeated freezing and thawing and store at -70C. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap
Molekulargewicht:
75000
Reinheit:
95% (SDS-PAGE)
Formulierung:
Supplied as a liquid in 50mM sodium phosphate, 150mM sodium chloride, pH 7.4.
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