Localization of two unique heparin binding domains of human plasma fibronectin with monoclonal antibodies.

Monoclonal antibodies to human plasma fibronectin were used to study the topological arrangement of several biologically active sites on the 220,000-dalton fibronectin subunit. Plasma fibronectin was cleaved into a number of biologically active fragments by trypsin and cathepsin D. Fragments that bind gelatin and heparin bind to both gelatin and heparin were isolated by affinity chromatography. These fragments were further characterized by their ability to bind to two different monoclonal antibodies: monoclonal 2-8 and monoclonal 180-8. Using this approach, we have established the positions of two unique heparin-, a gelatin-, and two monoclonal antibody-binding sites on the fibronectin subunit.