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.