Abstract
Free and matrix-bound phosphoprotein (phosphophoryn) fractions were extracted from the bovine incisor dentin, and purified by DEAE-cellulose, SP-Sephadex and gel filtration chromatography. Both components were eluted in broad peaks, when chromatographed on gel filtration column even in dissociative conditions, indicating the predominance of aggregative tendency of phosphophoryn. On SDS-polyacrylamide gel electrophoresis, both components migrated in sharp bands. However, the apparent molecular weights, estimated from the mobilities of standard globular proteins, varied depending on the gel concentration. This non-ideal behavior of phosphophoryn might be due to the effect of its polyanionic structure.
Matrix-bound phosphophoryn is thought to be a tight complex of phosphophoryn and collagen peptides. This complex was different from simple non-covalent association products of these components. Both free and matrix-bound phosphophoryns contained lysinoalanine. But this amino acid could not be a candidate for the cross-link between phosphophoryn and collagen.
The possible role of phosphophoryn in calcification of dentin was discussed.
