The isolation of anionic phosphoproteins from bovine cortical bone Via the periodate solubilization of bone collagen

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.