Distribution of secondary structure along the fibronectin molecule.

30-kDa, 50-kDa and 70-kDa gelatin-binding, 60-kDa central and 60-65-kDa heparin-binding fragments were produced by trypsin digestion of fibronectin. The secondary structure of the fragments was studied by circular dichroism and quantitative infrared spectroscopy. The structure of the 70-kDa gelatin-binding, 60-kDa central and 60-65-kDa heparin-binding fragments in solution appeared to be very close to that in the intact fibronectin. The content of the antiparallel beta-form, the only element of the secondary structure in all the fragments studied, was shown to be 30-35%.