Recombinant Mouse DMP-1 Protein, CF

Dentin matrix protein 1 (DMP-1) is a member of the SIBLING family of proteins that includes bone sialoprotein, dentin sialophosphoprotein, MEPE, and osteopontin. These are highly phosphorylated integrin-binding proteins that are rich in acidic amino acids and function in the formation of calcified bone and tooth matrix (1, 2). Its phosphate content, spacing of acidic residues, and calcium-dependent dimerization of DMP-1 contribute to its ability to sequester calcium phosphate clusters and promote hydroxyapatite (HA) crystal formation (3-5). Mature mouse DMP-1 is 487 amino acids (aa) in length. It contains a poly-Pro segment (aa 41-44) and an RGD binding motif (aa 350-352). DMP-1 may be cleaved by BMP-1 family proteases at a single site which is conserved in human, generating a 37 kDa N-terminal (aa 17-212) and a 57 kDa C-terminal (aa 213-503) fragment (6). The N-terminal fragment in rat carries chondroitin sulfate (7). The C-terminal fragment alone can nucleate HA crystals, while crystal growth into a needle-like morphology is inhibited by the N-terminal fragment (3, 4). Crystal maturation is dependent on the presence of type I collagen (4). DMP-1 is required for odontoblast differentiation as well as dentin formation (8). Nonphosphorylated DMP-1 is retained intracellularly where it is targeted to the nucleus. Here, it activates the transcription of odontoblast and osteoblast specific genes (9, 10). Early in osteoblast maturation, nuclear DMP-1 is extensively phosphorylated by casein kinase II, triggering its secretion (9). DMP-1 mutations in humans are associated with hypophosphatemia and FGF23 overexpression (11, 12). DMP-1 induces the activation of proMMP-9 and displaces mature MMP-9 from TIMP1 (13). DMP-1 tethers MMP-9 to the cell surface via CD44 and integrins alpha V beta 3 and alpha V beta 5, promoting tumor cell invasiveness in vitro (14). Full length DMP-1 circulates in human serum in a tight complex with complement factor H (13, 14). When first bound to CD44 or integrin alpha V beta 3, DMP-1 can anchor factor H to the cell surface and protect the cell from complement-mediated lysis (15). Mature mouse DMP-1 shares 63%, 61%, and 87% aa sequence identity with bovine, human, and rat DMP-1, respectively.