Purified, decalcified bovine bone matrix was partially solubilized by prolonged oxidative degradation with sodium metaperiodate. Fractionation of a portion of the solubilized bone matrix on DEAE-cellulose led to the isolation of two anionic components (0.55 and 0.75 M NaCl elutions). Analysis showed each component to be a protein characterized by a high content of aspartic and glutamic acids, serine and glycine. A substantial portion of the serine was present as serine phosphate in both compounds. Galactosamine was found in the component eluted with 0.55 M NaCl and this fraction probably represents degraded protein-polysaccharide. The other component, eluted with 0.75 M NaCl, contained no hexosamine but did contain hydroxylysine. Disc electrophoresis showed this component to be similar to a phosphoprotein isolated from dentin collagen. The possible relationship between the bone and dentin phosphoproteins and their role in mineralization is discussed.
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