Integrin-binding sialoprotein gene mapped on chromosome 4q21.1 that contains 7 exons at approximately 70kD that undergoes posttranslational modifications which constitutes of 12% noncollagenous proteins in human bone synthesized by skeletal cell types, hypertrophic chondrocytes, osteoblasts, osteoclasts and osteocytes as such trophoblast is the only extraskeletal sites of its synthesis.
Integrin-binding sialoprotein is a major structural protein of bone matrix that binds to calcium and hydroxypatite via its acidic amino acid clusters and intercede cell attachment though an RGD sequence that recognizes the vitronectin receptor. It is extremely glycosylated and sulfated phosphoprotein that is present almost entirely in mineralized connective tissues.
Integrin-binding sialoprotein expressed in adult kidney mostly in nephron segments. It enhances osteogenic cell migration through basement membrane and collagen matrices by localizing MMP-2 on the cell surface through alpha/beta integrin. It is a member of SIBLING (small integrin-binding ligand N-linked glycoprotein) family that are recognized to construct non-collagenous extracellular matrices of calcified tissues arisen by duplication and subsequent divergent evolution of a single ancient gene thereby IBSP molecule might gradually intensified its functions related to calcification during its evolutionary process.
Gene name: IBSP
Protein name: Bone sialoprotein 2