Vitronectin (VTN), a member of the pexin family, is an abundant glycoprotein found in serum, the extracellular matrix and bone. It is a secreted protein and exists in either a single chain form or a clipped, two chain form held together by a disulfide bond. VTN consists of three domains: the N-terminal Somatomedin B domain, a central domain with hemopexin homology, and a C-terminal domain also with hemopexin homology.
VTN promotes cell adhesion and spreading, inhibits the membrane-damaging effect of the terminal cytolytic complement pathway, and binds to several serpins (serine protease inhibitors). It has been speculated to be involved in hemostasis, cell migration and tumor malignancy.