Domain Structure of Beta Thromboglobulin
The domain structure of the β-thromboglobulin monomer is represented. The β-thromboglobulin monomer is an 8,800 molecular weight peptide which is derived via NH2-terminal proteolysis of a precursor molecule LAPF-4 (low affinity platelet factor-4). Although the COOH-terminal domain of β-thromboglobulin is characterized by a clustering of basic lysine residues, the affinity of b-thromboglobulin for heparin is significantly weaker than that of platelet factor-4. In its native state, β-thromboglobulin is a homotetramer consisting of four, identical, noncovalently-
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Size 100 µg Formulation 25 mM Hepes, 150 mM NaCl, pH 7.4 Storage -80°C Purity >95% by SDS-PAGE Activity Determination N/A Shelf Life (properly stored) 12 months
β-thromboglobulin (b-TG), is a low molecular weight, heparin-binding, platelet-derived protein (1). It is similar to platelet factor-4 (PF-4) in that it is localized within the platelet alpha-granule at levels reported to range from 8.1-24.2 µg per 109 platelets (2,3). The relative concentration of β-TG in platelets exceeds that of plasma by 260,000-fold (4) making β-TG a convenient marker of platelet activation. Structurally, β-TG is analogous to PF-4 in that, in its native state, β-TG is a tetramer (1) consisting of four identical 8800 molecular weight peptide chains (5). In contrast to PF-4, β-TG exhibits a lower affinity for heparin and also exists as a larger molecular weight species known as "low affinity PF-4" (LAPF-4) (2). β-TG is derived from the proteolytic removal of four NH2-terminal amino acid residues from a LAPF-4 (6,7). Immunological screening of partially fractionated supernatant from activated platelets revealed a highly basic form of β-TG distinct from LAPF-4 (7). This basic β-TG species, termed platelet basic protein (PBP), was subsequently isolated (8) and later concluded from immunological, peptide sequencing, and proteolytic processing studies to be a higher molecular weight precursor form of both LAPF-4 and β-TG (9,10).
The physiological function of β-TG is not known. While early studies suggested that the precursor forms of β-TG were mitogenic for mouse fibroblasts (8,11), it was later concluded that this activity was due to growth factor contamination (10). β-TG has also been reported to inhibit prostacyclin-I2 production by endothelial cells (12), however, the relevance of this effect has been called into question (13,14). The chemotactic activity of platelet alpha-granule proteins for human fibroblasts has been attributed to both PF-4 and β-TG (15).
Human β-TG is prepared from the supernatant of activated platelets by heparin-agarose affinity chromatography and gel filtration (1,2). The purified protein is supplied in 25 mM Hepes, 150 mM NaCl pH 7.4 and should be stored at -80°C. Purity is assessed by SDS-PAGE analysis.
|Gel||Novex 4-12% Bis-Tris|
|Load||Load: Human Beta Thromboglobulin, 1 µg per lane|
|Standard||SeeBluePlus 2; Myosin (188 kDa), Phosphorylase B (98 kDa), BSA (62 kDa), Glutamic Dehydrogenase (49 kDa), Alcohol Dehydrogenase (38 kDa), Carbonic Anhydrase (28 kDa), Myoglobin Red (17 kDa), Lysozyme (14 kDa), Aprotinin (6 kDa), Insulin, B chain (3 kDa).|
|Localization||platelet alpha-granule (3)|
|Plasma Concentration||100-200 µg/ml|
|Mode of action||heparin-binding protein: Plasma concentration used as a marker of platelet activation|
|Molecular weight||35,800 (1)|
|Structure||homotetramer (monomer, Mr~8800) (5)|
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No sample publications.