FN3

Fibronectin type 3 domain
FN3
SMART accession number:SM00060
Description: One of three types of internal repeat within the plasma protein, fibronectin. The tenth fibronectin type III repeat contains a RGD cell recognition sequence in a flexible loop between 2 strands. Type III modules are present in both extracellular and intracellular proteins.
Interpro abstract (IPR003961):

Fibronectin is a dimeric glycoprotein composed of disulfide-linked subunits with a molecular weight of 220-250 kDa each. It is involved in cell adhesion, cell morphology, thrombosis, cell migration, and embryonic differentiation. Fibronectin is a modular protein composed of homologous repeats of three prototypical types of domains known as types I, II, and III [(PUBMED:6218503)].

Fibronectin type-III (FN3) repeats are both the largest and the most common of the fibronectin subdomains. Domains homologous to FN3 repeats have been found in various animal protein families including other extracellular-matrix molecules, cell-surface receptors, enzymes, and muscle proteins [(PUBMED:1409594)]. Structures of individual FN3 domains have revealed a conserved beta sandwich fold with one beta sheet containing four strands and the other sheet containing three strands (see for example {PDB:1TEN}) [(PUBMED:1279805)]. This fold is topologically very similar to that of Ig-like domains, with a notable difference being the lack of a conserved disulfide bond in FN3 domains. Distinctive hydrophobic core packing and the lack of detectable sequence homology between immunoglobulin and FN3 domains suggest, however, that these domains are not evolutionarily related [(PUBMED:1279805)].

FN3 exhibits functional as well as structural modularity. Sites of interaction with other molecules have been mapped to short stretch of amino acids such as the Arg-Gly-Asp (RGD) sequence found in various FN3 domains. The RGD sequences is involved in interactions with integrin. Small peptides containing the RGD sequence can modulate a variety of cell adhesion invents associated with thrombosis, inflammation, and tumor metastasis. These properties have led to the investigation of RGD peptides and RGD peptide analogs as potential therapeutic agents [(PUBMED:8548820)].

GO function:protein binding (GO:0005515)
Family alignment:
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There are 158597 FN3 domains in 48392 proteins in SMART's nrdb database.

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