For FY 1994 the Protein Biochemistry Program continued its interest in structure-function studies and was involved in one major project and several smaller collaborations. The major project was to identify the specific portions of the bone sialoprotein (BSP) that are involved in the two commonly accepted functions of this sulfated phosphoglycoprotein, cell attachment and the putative ability to nucleate hydroxyapatite crystals. We have identified two cell attachment domains that do not directly involve the cell attachment tripeptide ArgGlyAsp (RGD). The mineral- binding properties appear to be spread over the middle two-thirds of the protein rather than being limited to a small domain. In collaboration with Dr. Dennis Torchia, we have determined that the integrin-binding 59 amino acid RGD domain is a highly flexible coil. Two types of collaborations with scientists outside of NIDR also involve BSP. With Dr. Paulo Bianco in Rome, Italy we are continuing to study the synthesis and secretion of BSP by bone cells and trophoblasts. With two other laboratories in Europe, we are studying the usefulness of BSP as a marker of bone cancers as well as other tumors (breast and prostate cancers) that frequently form mineralized nodules and also metastasize to bone. With Dr. Deutsch in Israel we have continued the collaborative studies on the enamel protein, tuftelin, including human gene sequencing, chromosomal localization, and surveying non sex-linked amelogenesis imperfecta families in Israel. We have completed our collaborations with two groups in involving the human biglycan gene/promoter and its activation status on the X chromosome in human females. A collaboration with a colleague in Israel involving a cDNA clone we discovered that may be a marker of bone stem cells in mice has continued. Finally, our program has sent nearly 400 reagents to over 100 laboratories around the world, over 10% of which were in the dental field.
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