Figure 22-22. Structure of fibronectin chains.

Figure 22-22Structure of fibronectin chains

Only one of the two chains present in the dimeric fibronectin molecule is shown; both chains have very similar sequences. Each chain contains about 2446 amino acids and is composed of three types of repeating amino acid sequences. Circulating fibronectin lacks one or both of the type III repeats designated EDA and EDB owing to alternative mRNA splicing. At least five different sequences may occur in the IIICS region as the result of alternative splicing. Each chain contains six domains (tan ovals) containing specific binding sites for heparan sulfate, fibrin (a major constituent of blood clots), denatured forms of collagen, and cell-surface integrins. Binding to integrins is dependent on an Arg-Gly-Asp (RGD) sequence. Heparan sulfate and fibrin have binding sites in a shared domain, and each has another binding site in its own, unshared domain; these sites differ in their affinity for the ligand. [Adapted from G. Paolella, M. Barone, and F. Baralle, 1993, in M. Zern and L. Reid, eds., Extracellular Matrix, Marcel Dekker, pp. 3 – 24.]

From: Section 22.2, Cell-Matrix Adhesion

Cover of Molecular Cell Biology
Molecular Cell Biology. 4th edition.
Lodish H, Berk A, Zipursky SL, et al.
New York: W. H. Freeman; 2000.
Copyright © 2000, W. H. Freeman and Company.

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