POLYSACCHARIDES OF INTRACRYSTALLINE GLYCOPROTEINS MODULATE CALCITE CRYSTAL-GROWTH IN-VITRO

Assemblies of glycoproteins from within the mineralized tissues of sea urchins and mollusks both interact in vitro in a similar manner with growing calcite crystals. A protein-rich fraction, a polysaccharide-ri ch fraction, and a fraction composed of densely glycosylated peptide c ores were obtained by chemical and enzymatic treatment of the glycopro teins from sea-urchin spines. Each fraction was partially purified and characterized (amino acid composition, FTIR and NMR spectroscopy). A comparison of the interactions of these fractions with growing calcite crystals in vitro shows that the polysaccharide moieties of these gly coproteins are intimately involved in the interaction with growing cal cite crystals on planes approximately parallel to the c crystallograph ic axis. Presumably the polysaccharides in the mollusk-shell glycoprot eins are likewise responsible for the similar interactions of these ma cromolecules with calcite. We suggest that structured polysaccharide m oieties of glycoproteins are important in controlling aspects of cryst al growth in vivo as well.