Fibrinogen

Fibrinogen is the clotting element present in blood. When blood comes out of a wound in a vessel, the fibrinogen is activated and forms fibrin, which clots the blood. Although this is fibrinogen's main job, it also forms bridges between platelets. Fibrinogen is a protein made by the liver. It is a dimer (made up of two similar units). Each unit has an alpha, beta, and gamma chain. The alpha and beta chains have a small peptide called fibrinopeptide.

When fibrinogen is activated to form fibrin, an enzyme called thrombin cleaves the fibrinopeptides off of the alpha and beta chains.

It is possible to examine a small sample of a person's blood to find out how much fibrinogen is in the blood. This helps medical professionals to know if too much or too little fibrinogen is the cause of a patient's medical problems.

Fibrinogen Media

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  Human fibrinogen. Aα chains (cyan), Bβ chains (red), γA chains (pink), calcium (green), carbohydrated (orange). FpA: fibrinopeptides A. FpB: fibrinopeptides B. αC: Aα chain C-terminal domain. D: D domain. E: E domain.

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  Human fibrinogen (PDB: 3GHG). Colors are the same as in the other picture. Disulfide bonds are also shown (highlighted with yellow). Parts of the actual structure are unresolved: e.g., the C-terminals of Aα chains are too short.