IBSP (integrin-binding sialoprotein, also BSP or bone sialoprotein (II)) is a 55-75kD, secreted, variably glycosylated, monomeric noncollagenous member of the SIBLING family of extracellular matrix (ECM) proteins. It is principally associated with the early stages of bone mineralization. BSP is synthesized as a 317 amino acid (aa) precursor that contains a 16aa signal sequence and a 301aa mature region. BSP is highly glycosylated, sulfated, and phosphorylated. Phosphorylation may impact HAp growth, while carbohydrate may regulate cell adhesion. Mature human BSP is 70%, 72%, 78%, and 72% aa identical to porcine, rat, canine, and mouse BSP, respectively. BSP is synthesized by megakaryocytes/platelets, osteoblasts, osteocytes, odontoblasts, osteoclasts, and bone marrow stromal cells. Recombinant protein corresponding to Phe17-Gln317 with a C-Terminal 10-His Tag from human human BSP, expressed in CHO cells (AAC95490). Molecular Mass: Recombinant human BSP migrates as an ~75-90kD protein in SDS-PAGE under reducing conditions. Activity: Measured by the ability of the immobilized protein to support the adhesion of MCF-7 cells. When 5x10e4 MCF-7 cells/well are added to recombinant human IBSP-coated plates (3ug/ml with 100ul/well), ~60-80% will adhere after 30 minutes at 37C. Optimal concentration depends on cell type. Storage and Stability: Lyophilized and reconstituted products are stable for 6 months after receipt at -20C. Reconstitute with sterile PBS. Aliquot to avoid repeated freezing and thawing. Store at -20C. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap. Further dilutions can be made in assay buffer.
