Recombinant expression and characterization of dentin matrix protein 1

Dentin matrix protein 1 (DMP1) is an extracellular matrix noncollagenous pr otein (NCP) initially isolated from dentin and now found to be present in c alcified tissues like calvaria and long bone. The characteristic feature of DMP1 is that it contains a large number of acidic domains and has properti es which implicate it as a key participant in regulating matrix mineralizat ion. The level of DMP1 in the tissue is sparse and it is not easily isolate d from dentin because it copurifies with other dentin NCPs. The exact funct ion of DMP1 is not known and this is due to the inherent difficulty of obta ining enough protein from the mineralized tissues. In order to understand t he physiologic role for DMP1 during the formation of mineralized tissues we have produced milligram quantities of recombinant DMP1 in E. coli. The obj ective of this work was: (1) to prepare unmodified apoprotein so that it co uld be used for studying the function of DMP1; and (2) to prepare polyclona l antibody against the recombinant DMP1 antigen. The DMP1 polyclonal antibo dy did not cross-react with other NCPs present in dentin or with bone acidi c glycoprotein-75 (BAG-75) present in the bone matrix, confirming the speci ficity of this antibody and thus making it a valuable tool to determine the in vivo function of DMP1.