Hydrophobic properties of porcine fibronectin and its functional domains

The relations between surface hydrophobicities and binding properties of the functional domains of porcine plasma fibronectin were investigated. Porcine plasma fibronectin as well as human plasma fibronectin was adsorbed on a hydrophobic column with butyl or phenyl ligands in the presence of 0.5 M ammonium sulfate, and recovered in a single peak by decreasing the concentration of ammonium sulfate to 0 M, indicating that both fibronectins have very high surface hydrophobicities. On digestion with thermolysin, porcine plasma fibronectin yielded five fragments (140-150, 43, 25, 17, and 14 kDa) similar to those reported for human fibronectin, although porcine fibronectin was more resistant to the digestion than human fibronectin. The three heparin-binding fragments were found to have a wide range of surface hydrophobicities, the 140-150 kDa fragment having the lowest, the 25 kDa fragment a higher, and the 14 kDa fragment the highest among all the fragments. The 43 kDa collagen-binding and 17 kDa fragments had surface hydrophobicities as high as that of fibronectin. It is noteworthy that the 43 kDa collagen-binding fragment contributes to the high surface hydrophobicity of intact fibronectin in spite of the high content of carbohydrates.