Definition: Fibrinogen is an essential protein in coagulation cascade.
Fibrinogen is produced in the hepatocyte from 3 homologous polypeptide chains, Aα (FGA), Bβ (FGB), and γ (FGG), which assemble to form the hexameric structure (AαBβγ)2.
The hexamer is characterized by a symmetrical trinodal (D-E-D) structure, with a central E domain connected to 2 peripheral D domains.
The E domain, which comprises the N-terminal ends of all 6 chains, is prolonged by two three-stranded coiled-coil regions composed of each chain, and terminates in 2 globular D domains comprising the C-termini of the Bβ-and γ-chains.
Mechanisms of fibrinogen assembly have been well studied. Assembly occurs in the endoplasmic reticulum (ER) with the formation of an Aα-γ or Bβ-γ intermediate. The addition of a Bβ or Aα chain respectively gives rise to a [Aα-Bβ-γ] half-molecule, which then dimerizes to form the hexamer.
Further modifications occur in the golgi network and include modifications of the N-linked oligosaccharides, hydroxylation, phosphorylation, and sulfation.
Pathology
genetic diseases of fibrinogen