Vitronectin binds to heparin, collagen, streptococci and variety of cultured cells. It also acts as an inhibitor of the complement cascade by binding to the C5b-9 complex. Vitronectin protects thrombin from inactivation by antithrombin III in the presence of heparin, binds and stabilizes the activity of plasminogen activator inhibitor and mediates many other physiological functions.
