Different forms of DMP1 play distinct roles in mineralization

Dentin matrix protein-1 (dmp1) is a major synthetic product of hypertrophic chondrocytes and osteocytes. previous in vitro studies showed full-length dmp1 inhibits hydroxyapatite (ha) formation and growth,while its n-terminal fragment (37k) promotes ha formation. since there are 3 fragments within the mineralized tissues [n-terminal,c-terminal (57k),and a chondroitin-sulfate-linked n-terminal fragment (dmp1-pg)],we predicted that each would have a distinct effect on mineralization related to its interaction with ha. in a gelatin-gel system,37k and 57k fragments were both promoters of ha formation and growth; dmp1-pg was an inhibitor. the secondary structures of the 3 fragments and the full-length protein in the presence and absence of ca2+ and ha determined by ftir showed that the full-length protein undergoes slight conformational changes on binding to ha,while 37k,57k,and dmp1-pg do not change conformation. these findings indicate that distinct forms of dmp1 may work collectively in controlling the mineralization process.