Fibronectin domain structure

The domain structure in fibronectins is made up of a few types of peptide module that are repeated numerous times. Each of the more than 50 modules is coded for by one exon in the fibronectin gene. Alternative splicing (see p. 246) of the hnRNA transcript of the fibronectin gene leads to fibronectins with different compositions. The module that causes adhesion to cells contains the characteristic amino acid sequence -Arg-Gly-Asp-Ser-. It is these residues that enable fibronectin to bind to cell-surface receptors, known as integrins. 

Figure 1 Schematics of the domain structures of the MMP family. The catalytic domain (represented by light purple) has an insertion of gelatin binding domain (fibronectin type-ll-like domain) in MMP-2 and MMP-9. In all other MMPs, the catalytic domain is a continuous entity. Transmembrane and cytoplasmic regions (represented by yellow) are found in membrane-bound MMPs only.

Sekiguchi, K., Siri, A., Zardi, L., and Hako-mori, S. (1985) Differences in domain structure between human fibronectins isolated from plasma and from culture supernatants of normal and transformed fibroblasts. Studies with domain-specific antibodies, J Biol Ghem 260, 5105-5114. 

Fig. I. Domain structure of MMPs. The hemopexin domain has a four-bladed propeller configuration. The pre domain is cleaved before exit from the endoplasmic reticulum. MMP-7 lacks the hemopexin domain. MMP-2 and MMP-9 contain fibronectin-binding domains. MT-MMPs (-1, -2, -3, -5) contain a transmembrane and a cytoplasmic domain.

Figure 48-3. Schematic representation of fibronectin. Seven functional domains of fibronectin are represented two different types of domain for heparin, cell-binding, and fibrin are shown. The domains are composed of various combinations of three structural motifs (I, II, and III), not depicted in the figure. Also not shown is the fact that fibronectin is a dimer joined by disulfide bridges near the carboxyl terminals of the monomers. The approximate location of the RGD sequence of fibronectin, which interacts with a variety of fibronectin integrin receptors on cell surfaces, is indicated by the arrow. (Redrawn after Yamada KM Adhesive recognition sequences.

Brummendorf, T. and Rathjen, F. G. Axonal glycoproteins with immunoglobulin and fibronectin type II-related domains in vertebrates Structural features, binding activities and signal transduction. /. Neurochem. 61 1207-1219, 1993. 

The extracellular domain of RPTKs can be composed of different structural motifs. For instance, the EGFR extracellular domain contains two cysteine-rich regions. The PDGFR extracellular domain consists of five immuno-globulin-like repeats. Other domains found in the extracellular region of RPTKs include fibronectin III repeats,... 

---