Post-translational modification of osteopontin: Effects on in vitro hydroxyapatite formation and growth

► Thrombin-cleaved fragments of milk-osteopontin effect hydroxyapatite formation differently. ► N- and C-terminal fragments promoted hydroxyapatite formation and growth. ► A central fragment inhibited hydroxyapatite formation and growth. ► Binding to collagen or hydroxyapatite seed crystals modified these effects.