Fibronectin, type I repeats are one of the three repeats found in the

fibronectin Fibronectin is a high- molecular weight (~500-~600 kDa) glycoprotein of the extracellular matrix that binds to membrane-spanning receptor proteins called integrins. Fibronectin also binds to other extracellular matrix proteins such as collage ...

protein. Fibronectin is a plasma protein that binds cell surfaces and various compounds including

collagen Collagen () is the main structural protein in the extracellular matrix found in the body's various connective tissues. As the main component of connective tissue, it is the most abundant protein in mammals, making up from 25% to 35% of the whole ...

fibrin Fibrin (also called Factor Ia) is a fibrous, non-globular protein involved in the clotting of blood. It is formed by the action of the protease thrombin on fibrinogen, which causes it to polymerize. The polymerized fibrin, together with platele ...

heparin Heparin, also known as unfractionated heparin (UFH), is a medication and naturally occurring glycosaminoglycan. Since heparins depend on the activity of antithrombin, they are considered anticoagulants. Specifically it is also used in the treatm ...

, DNA, and

actin Actin is a family of globular multi-functional proteins that form microfilaments in the cytoskeleton, and the thin filaments in muscle fibrils. It is found in essentially all eukaryotic cells, where it may be present at a concentration of over ...

. Type I domain (FN1) is approximately 40 residues in length. Four conserved cysteines are involved in

disulfide bond In biochemistry, a disulfide (or disulphide in British English) refers to a functional group with the structure . The linkage is also called an SS-bond or sometimes a disulfide bridge and is usually derived by the coupling of two thiol groups. In ...

s. The 3D structure of the FN1 domain has been determined. It consists of two antiparallel beta-sheets, first a double-stranded one, that is linked by a disulfide bond to a triple-stranded beta-sheet. The second conserved disulfide bridge links the C-terminal adjacent strands of the domain. In human tissue plasminogen activator chain A the FN1 domain together with the following epidermal growth factor (EGF)-like domain are involved in fibrin-binding. It has been suggested that these two modules form a single structural and functional unit. The two domains keep their specific tertiary structure, but interact intimately to bury a hydrophobic core; the inter-module linker makes up the third strand of the EGF-module's major beta-sheet.

Human proteins containing this domain

F12; FN1;

HGFAC Hepatocyte growth factor activator is a protein that in humans is encoded by the HGFAC gene. The protein encoded by this gene belongs to peptidase family S1. It is first synthesized as an inactive single-chain precursor before being activated to ...

;

PLAT In the United States, a plat ( or ) (plan) is a cadastral map, drawn to scale, showing the divisions of a piece of land. United States General Land Office surveyors drafted township plats of Public Lands Surveys to show the distance and bear ...

;

References

{{InterPro content, IPR000083 Protein domains