Figure 3.

Domain structure of human fibronectin (based on SMART-tool [176] and review [177]). Each monomer contains three types of repeats: fibronectin type I (green ovals), type II (orange) and type III (gold rectangles). One or both of the FN type III modules (ED-A or ED-B) may be present in cellular fibronectin (cFN) but never in plasma fibronectin (pFN). A “variable” V or IIICS region is located between FNIII14 and FNIII15 and spliced out in ~50% subunits of pFN [178]. Two subunits are linked by a pair of C-terminal disulfide bonds to form a protein dimer. FNIII14 and “FN fragment” are proteolytic bioactive fragments derived from fibronectin.