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Fibronectin type 1 domain, approximately 40 residue long with two conserved disulfide bridges. FN1 is one of three types of internal repeats which combine to form larger domains within fibronectin. Fibronectin, a plasma protein that binds cell surfaces and various compounds including collagen, fibrin, heparin, DNA, and actin, usually exists as a dimer in plasma and as an insoluble multimer in extracellular matrices. Dimers of nearly identical subunits are linked by a disulfide bond close to their C-terminus. FN1 domains also found in coagulation factor XII, HGF activator, and tissue-type plasminogen activator. In tissue plasminogen activator, FN1 domains may form functional fibrin-binding units with EGF-like domains C-terminal to FN1.
Jiyao W et al.(2023). "The conserved domain database in 2023.",