Vitronectin is a cell adhesion and spreading factor found in serum and tissues. Vitronectin interact with glycosaminoglycans and proteoglycans. Is recognized by certain members of the integrin family and serves as a cell-to-substrate adhesion molecule. Inhibitor of the membrane-damaging effect of the terminal cytolytic complement pathway (By similarity). Monomer. Interacts with SERPINE1/PAI1 and C1QBP (By similarity). Plasma. The SMB domain mediates interaction with SERPINE1/PAI1. Sulfated on tyrosine residues. N- and O-glycosylated. It has been suggested that the active SMB domain may be permitted considerable disulfide bond heterogeneity or variability, thus two alternate disulfide patterns based on 3D structures are described with 1 disulfide bond conserved in both.