Structure
Fibrinogens are molecules that are usually found in the blood plasma. It is a 340-kDa glycoprotein composed of two sets of disulfide-bridged Alpha-, Beta-, and gamma-chains (Weisel & Litvinov, 2017). Fibrinogen is formed after FGA, FGB, and FGG links. These genes are clustered around the human chromosome 4, which consequently translates to polypeptides of the pre-pro-Aα chain (644 amino acid residues), pre-pro-Bβ chain (491 residues), and pre-pro-γ chain (437 residues) (Weisel & Litvinov, 2017). Before being released into the blood, the polypeptides chains are assembled. This allows them to perform their primary function of stopping bleeding.
Functions
Fibrinogen is essential for blood clot formation, which helps to stop bleeding. It works by forming an insoluble clot when converted to fibrin through the serine protease thrombin activated through an enzymatic reaction triggered by an injury (Weisel & Litvinov, 2017). To achieve proper functioning, the conversion of fibrinogen to fibrin during clotting and the clot dissolution should be balanced. In case of imbalance, for example, if the clotting is prevalent, a blood clot that could block blood flow could occur, and it can lead to thrombosis. At the same time, less fibrinogen could lead to excessive bleeding. The fibrinogen protein, therefore, helps prevent hypercoagulability and dissolve clots.
Importance in Blood Circulation
As mentioned, fibrinogen is essential in blood circulation because, when properly balanced, it can prevent the formation of clots that could prevent the movement of blood through the blood vessels. Furthermore, fibrinogen provides support to homeostasis, which is the state at which bleeding is controlled naturally. A defect in a hemostatic protein like fibrinogen can lead to pathological hemorrhage. Therefore, the fibrinogen plasma levels must be on a level that can support hemostasis.
References
Weisel, J. W., & Litvinov, R. I. (2017). Fibrin formation, structure, and properties. Fibrous proteins: structures and mechanisms, 405-456.