Characterization of recombinant human cementum protein 1 (hrCEMP1): primary role in biomineralization.

Cementum protein 1 (CEMP1) has been recently cloned, and in vitro experiments have shown functions as regulator of cementoblast behavior and inducer of differentiation of non-osteogenic cells toward a cementoblastic/osteoblastic phenotype. In this study, we have produced a full-length human recombinant CEMP1 protein in a human gingival fibroblast cell line. The purified protein (hrCEMP1) has a M(r) 50,000. Characterization of hrCEMP1 indicates that its secondary structure is mainly composed of beta-sheet (55%), where random coil and alpha helix conformations correspond to 35% and 10%, respectively. It was found that hrCEMP1 is N-glycosylated, phosphorylated and possesses strong affinity for hydroxyapatite. Even more important, our results show that hrCEMP1 plays a role during the biomineralization process by promoting octacalcium phosphate (OCP) crystal nucleation. These features make CEMP1 a very good candidate for biotechnological applications in order to achieve cementum and/or bone regeneration.