Osteonectin (SPARC) Protein

Osteonectin is an acidic, noncollagenous glycoprotein (Mr=29,000) originally isolated from fetal and adult bovine bone matrix (1-5). In vitro bovine bone osteonectin binds type I collagen, calcium (Kd=3x10(-7)M) and hydroxyapatite (Kd=8x10(-8)M) and has been shown to be a potent inhibitor of hydroxyapatite seeded crystal growth (6). In this context it has been suggested that osteonectin may play an important role in the regulation of bone metabolism by binding hydroxyapatite to collagen.

Recently, proteins homologous to osteonectin nave been identified in a number of cell types, most of which are associated with extracellular matrix production (7). The amino acid sequence (from cDNA sequences) of one of these proteins, human placental SPARC, is identical to human bone osteonectin.
Osteonectin has also been identified as an alpha granule component of human platelets and is secreted during platelet activation. A small portion of the secreted osteonectin is expressed on the platelet cell surface in an activation-dependent manner (8). Purified platelet osteonectin is a single chain molecule which exhibits a slightly larger apparent molcular weight than that of osteonectin derived from bone (8). The NH2-terminal sequences of platelet and bone-derived osteonectin are identical, but the two proteins differ with regard to the extent of glycosylation (8-10).
Human platelet osteonectin is isolated from thrombin-activated platelets as described by Kelm, et al. (8). Bovine bone osteonection is isolated from demineralized bone by the method of Romberg, et al. (2).

Small volumes of SPARC protein vial(s) may occasionally become entrapped in the seal of the product vial during shipment and storage. If necessary, briefly centrifuge the vial on a tabletop centrifuge to dislodge any liquid in the container`s cap. Certain products may require to ship with dry ice and additional dry ice fee may apply.

MBS634726 is a protein targeting SPARC. Also known as Osteonectin, Human (SPARC, Secreted Protein, Acidic, Cysteine-rich, ON, OSN). Host: Human platelets.