Arrangement of attachment-promoting, self-association, and heparin-binding sites in horse serum fibronectin.

Chicken myoblasts require fibronectin (a dimeric protein with subunits of M, -230,000) for their attachment to a substratum.Large monomeric fragments (Mr -200,000) of horse serum fibronectin retain f u l l attachment-promoting activity and ability to bind to gelatin; digestion with chymotrypsin of fibronectin bound to gelatin-Sepharose yields a mixture of two attachmentpromoting fragments (M, = 160,000 and 135,000) and a single M, = 60,000 gelatin-binding fragment (Ehrismann, R., Chiquet, M., and Turner, D. C. (1981) J. Biot