Fibronectin Binds to Charge-Modified Proteins

Abstract

Binding of fibronectin to a variety of macromolecular ligands has been demonstrated in vitro. These include proteins such as collagen, fibrin, actin, Clq and fibronectin itself, but also glycosaminoglycans, DNA and polyamines. Furthermore, fibronectin interacts with the surface of animal cells and bacteria (reviewed in Ref. 1). Some of these interactions contribute to the organization of extracellular matrixes in cell cultures and in connective tissue. The binding of fibronectin to bacteria, collagen, fibrin and actin probably are important for the role of circulatory fibronectin as an opsonin. In many cases, fibronectin appears to bind denatured or modified ligands more readily than native ones. Thus binding of fibronectin to collagen (2) and actin (3) is enhanced by denaturation of these proteins. Fibronectin binds more efficiently to fibrin than to its parent molecular form fibrinogen (4). Conformational factors may also play a role in the binding of fibronectin to Clq (5). We have tested the effect of chemical modification on the interaction of fibronectin with several serum proteins. Modification of carboxyl groups of lysozyme, albumin and IgG caused these proteins to avidly bind to fibronectin. This modification also enhanced the self-association of fibronectin.