English
General description
Fibronectins are made of two subunits linked by disulfide bonds at the C terminal. In the extracellular matrix fibrils, fibronectins are further disulfide bonded into high molecular weight polymers. Fibronectin subunits vary in size between approximately 235 and 270 kD depending on tissue and species. Each subunit is made of repeating modules of three types: I, II, and III. There are 12 type I repeats, approximately 45 amino acids long, clustered in three groups, two adjacent type II repeats each 60 amino acids long, and 15-17 type III repeats each about 90 amino acids long. Type I and type II each contains two disulfide bonds, while type III lacks disulfide bonds. There are two free sulfhydryl groups per subunit at the type III repeat.
Recently a new region, type III1 repeat cloned from human placenta cDNA, was reported to participate in matrix formation. In an experiment employing antibodies for the analysisof fibronectin domains required for matrix assembly, the epitope that inhibited binding and insolubilization of labeled plasma fibronectin by fibroblasts, was identified on the type III1 and type I modules of fibronectin. This suggested a role for type III1 and type I in the mediation of fibronectin assembly. This finding was further supported by the ability of the 14 kDa fragment from the first two type III repeats of fibronectin to inhibit fibronectin matrix assembly.4 Recently recombinant fragment III1-C, modeled after the C-terminal two-thirds of the III1 repeat, was found to bind to fibronectin and induce spontaneous disulfide crosslinking of the fibronectin molecules into multimers, which resemble matrix fibrils
Application
Epithelial cells, mesenchymal cells, neuronal cells, fibroblasts, neural crest cells, endothelial cells
Biochem/physiol Actions
Promotes cross-linking of fibronectin to form matrix fibril-like multimers.
Packaging
Package size based on protein content
