Activation of Vitronectin (Serum Spreading Factor) Binding of Heparin by Denaturing Agents1

Vitronectin (serum spreading factor), a cell-adhesive glycoprotein present in mammalian serum, has previously been the subject of conflicting reports concerning its binding to heparin. Vitronectin purified from human plasma does not bind to heparin under physiological conditions, but it does so after treatment with denaturing agents including 8 M urea or 6 M guanidine-HC1, or heating at 100 degrees C for 5 min. These treatments seem to expose a heparin-binding site in vitronectin; this finding thus resolves the conflicts concerning this function.