Characterization of a 59 kDa gelatin-binding fragment of buffalo plasma fibronectin

Abstract

Limited proteolysis of buffalo plasma fibronectin (FN) by thermolysin yielded four gelatin-binding fragments of which, the major 59 kDa fragment, GBFl, was isolated by gelatin-Sepharose and heparin-Sepharose affinity columns. GBFl appeared during early phase of thermolysin digestion and remained intact even after 4 hr of digestion. GBF1 may be similar to 56 kDa gelatin-binding fragment of FNs from human and hamster plasma. But, it is more resistant to thermolysin cleavage. The fragment binds to heparin with low affinity. On the basis of the structure of human plasma FN, the modular structure of GBFl may be given as: ⁶Fn1 ¹Fn2 ²Fn2 ⁷Fn1 ⁸Fn1 ⁹Fnl ¹Fn3. Biophysical properties of GBF1 suggest an expanded native conformation. The interaction of the fragment with gelatin is <i>p</i>H-dependent and independent of NaCl concentration.