| Fibrinogen |
Articles about Fibrin |
Information AboutFibrinogen |
| CATEGORIES ABOUT FIBRIN | |
| coagulation system | |
| blood proteins | |
| acute phase proteins | |
Fibrin is a Protein involved in the clotting of blood. It is a fibrillar protein that is Polymerised to form a "mesh" that forms a Haemostatic plug or clot (in conjunction with Platelets ) over a wound site. Fibrin is made from its Zymogen fibrinogen, a soluble Plasma Glycoprotein that is synthesised by the Liver . Processes in the Coagulation cascade activate the zymogen Prothrombin to the Serine Protease Thrombin , which is responsible for converting fibrinogen into fibrin. Fibrin is then cross linked by Factor XIII to form a clot. FIBRIN GENERATION Fibrinogen is a 340-KD glycoprotein synthesised in the liver Hepatocytes and Megakaryocytes , which Normally has a concentration between 1.5 - 4.0 g/L (normally measured using the Clauss method) in blood plasma. Dysfunction or disease of the liver can lead to a decrease in fibrinogen production or the production of abnormal fibrinogen molecules with reduced activity ( Dysfibrinogenaemia ). Hereditary abnormalities of fibrinogen (the gene is carried on chromosome 4) are of both quantitative and qualitative in nature and include; Afibrinogenaemia , Hypofibrinogenaemia , Dysfibrinogenaemia , and Hypodysfibrinogenaemia . In its natural form, fibrinogen is useful in forming bridges between platelets, by binding to their GpIIb/IIIa surface membrane proteins; though fibrinogen's major use is as a precursor to fibrin. Fibrinogen is a symmetrical Dimer composed of 6 paired polypeptide chains. (alpha, beta, and gamma chains). On the alpha and beta chains, there is a small Peptide sequence (called a fibrinopeptide). It is these small peptides that prevent fibrinogen spontaneously forming polymers with itself. Fibrinogen, the principal protein of vertebrate blood clotting is an hexamer containing two sets of three different chains (α, β, and γ), linked to each other by disulfide bonds. The N-terminal sections of these three chains are evolutionary related and contain the cysteines that participate in the cross-linking of the chains. However, there is no similarity between the C-terminal part of the α chain and that of the β and γ chains. The C-terminal part of the β and γ chains forms a domain of about 270 amino-acid residues. As shown in the schematic representation this domain contains four conserved cysteines involved in two disulfide bonds. xxxxxxCxxxxxxxxxxxxCxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxCxxxxxCxxxxxxxxxxxxx |
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