[Extraction and characterization of phosphoproteins from chicken bone]

EDTA and HCl extracts of chicken bone were fractionated by a variety of techniques, including molecular sieving, ion exchange chromatography, and high performance liquid chromatography. Six different molecular weight phosphoproteins, 13K, 14K, 15K, 28K, 33K, and 70K dalton, were obtained. Further purified fractions were isolated by extraction of single bands from SDS electrophoresis gels. The amino acid composition of these phosphoproteins suggested the origin of the lower molecular weight phosphoproteins from higher molecular weight phosphoprotein during the purification process or maturation of the animal. In those instances, however, the amino acid composition and the degree of phosphorylation varied. This suggested the existence of genetically different phosphoproteins. Molecular weight 70K fraction included collagen component, indicating some of the phosphoproteins strongly bound to the collagen of the bone matrix.