IMMUNOCHEMICAL AND IMMUNOHISTOCHEMICAL STUDY OF THE 27 AND 29-KDA CALCIUM-BINDING PROTEINS AND RELATED PROTEINS IN THE PORCINE TOOTH GERM

Our previous report identified 27- and 29-kDa calcium-binding proteins in porcine immature dental enamel. In this study we revealed that the N-terminal amino acid sequences of the two proteins were identical: L LANPXGXIPNLARGPAGRSRGPPG. The sequence matches a portion of the amino acid sequence of the porcine sheath protein, sheathlin. Porcine tooth germs were investigated immunochemically and immunohistochemically usi ng specific antibodies raised against synthetic peptide that included residues 13-25 of this sequence. The affinity-purified antibodies reac ted with several proteins extracted from newly formed immature enamel in immunochemical analyses, especially protein bands mi grating at 62, 35-45, 29, and 27 kDa in SDS-polyacrylamide gels. The largest protein detected was a weak band near 70 kDa. In immunochemical analyses of p roteins extracted from the inner (old) immature enamel, the antibody r eacted faintly with the 27- and 29-kDa proteins. In immunohistochemica l preparations, the Golgi apparatus and secretory granules of the secr etory ameloblast, and the surface layer of immature enamel showed immu noreactivity. The immunoreactivity of immature enamel just beneath the secretory face of the Tomes' process was intense, No immunoreactivity was found in the Golgi apparatus of the maturation ameloblast, These results suggest that the 70-kDa protein, whose degradation might be ve ry fast, is the parent protein of the 27- and 29-kDa proteins.