Merck, F2006-2MG, Fibronectin human plasma

Fibronectin (FN) is a multifunctional glycoprotein, the gene of which is localized to human chromosome 2q34-36. This gene spans 75kb and contains 50 exons. The fibronectin structure consists of blocks of repeating peptide sequences that are homologous in nature and form functional unit arranged linearly on two subunit arms. It exists as two major isoforms, one soluble and one insoluble form. The former is present in plasma, whereas the insoluble form resides in tissues and extracellular matrix (ECM) of cartilage. There are around 20 different forms of fibronectin protein due to alternative splicing of a variable region and two type III exons called Extra Domains A and B.