Substitution (gamma335Trp-->Arg) in fibrinogen Fremantle causes diminished gamma chain expression and increased sialic acid content.

摘要

Fibrinogen, also known as coagulation factor I, is an acute phase glycoprotein with four oligosaccharide units attached per molecule. Fibrinogen is synthesised in the liver and the mature protein is assembled in a step-wise manner from individual Aalpha, Bbeta and y chains (1,2). A signal peptide directs each nascent chain into the lumen of the endoplasmic reticulum (ER) and following cleavage of the leader sequence, Aa-y and Bbeta-gamma intermediates are formed (2). After acquiring an additional Bbeta or Aa chain respectively, the resulting Aa-Bbeta-gamma half-molecules dimerise and the (Aa-Bbeta-gamma)_2 assembly proceeds to the Golgi for pruning and extension of the N-linked oligosaccharides attached to the Bbeta and y chains. Subsequent cleavage of the Aa chain propeptide is followed by secretion into the circulation.