Description
Fibronectin (FN) is a glycoprotein whose size ranges from 230 to 270 kDa and usually exists as a dimer, covalently linked by a pair of disulfide bonds at the C-termini. Each monomer consists of three repeating units: 12 Type I, 2 Type II, and 15–17 Type III domains, which account for 90% of the FN sequence. Structural homologs of the Type I, II, and III domains exist in other biomolecules, suggesting that FN evolved through exon shuffling. Despite originating from a single gene, as many as 20 different human variants and 12 different rodent and cow variant FN isoforms have been identified, indicating alternative splicing mechanisms unique to species and tissue development. FN is subcategorized as either plasma FN (pFN), predominantly synthesized by liver hepatocytes, or cellular FN (cFN), which is produced by a wide variety of cells, including fibroblasts, chondrocytes, myocytes, and synovial cells. pFN circulates in the blood at a high concentration (approximately 300 μg/mL), while cFN is locally secreted[1].
General Description
Native fibronectin purified from human plasma. Effective agent for promoting attachment of cells to commonly-used culture substrates.
Biochem/physiol Actions
Fibronectin is a high molecular mass extracellular matrix glycoprotein involved in many cellular processes, including tissue repair, embryogenesis, blood clotting, cell migration/adhesion, and embryogenesis and development. It is used in vitro as a substrate to enhance adherence and proliferation of many cell types. It has the capacity to bind to macromolecules such as collagen, fibrin, glycosaminoglycans, and Clq, apart from some bacteria.
Purification Methods
This glycoprotein contains 5-12% of carbohydrate. It has been purified by glycine fractionation and DEAE-cellulose chromatography. This material is dissolved in 0.25M Tris-phosphate buffer pH 7.0, diluted to 20% and glycine added gradually till 2.1M when the temperature falls to below 15o. The precipitate contains mainly fibrinogen. The supernatant is discarded, and the precipitate is treated with an equal volume of H2O, cooled (to 0o) and precipitated by adding EtOH to 16% (v/v) at -4o. The precipitate contains some CI (Cold Insoluble) globulin, fibronectin and small quantities of other proteins. To remove these the precipitate is dissolved in 0.25M Tris-phosphate buffer (pH 7.0) ca 0.5% and purified by DEAE-cellulose chromatography after diluting the buffer to 0.05M buffer. [Morrison et al. J Am Chem Soc 70 3103 1948, Mosesson & Umfleet J Biol Chem 245 5728 1970, Mosesson & Amrani Blood 56 145 1980, Akiyama & Yamada Adv Enzymol 59 51 1987.]
References
[1] Dalton, Caleb J. and Christopher A. Lemmon. “Fibronectin: Molecular Structure, Fibrillar Structure, and Mechanochemical Signaling.”Cells 10 9 (2021): 2443.
