Isolation, chemical and biological characterization of sulphated glycoproteins synthesized by rat buccal and palatal minor salivary glands in vivo and in vitro.

35S-labelled sulphated glycoproteins (SGP) were isolated from these glands after the incorporation of radiosulphate in vivo and in vitro by fractionation of tissue and medium extracts on Sepharose 4B and partial purification by DEAE-Sephacel anion exchange chromatography. Fractions were assessed for purity by SDS-PAGE and by cellulose-acetate electrophoresis. Molecular weights ranged from 34,000 to 5 X 10(6). It was notable that the molecular size of SGP from the in vitro media was generally lower than from the corresponding tissue fractions, particularly for the palatal samples. The fractions were heterogeneous and contained no sulphated glycosaminoglycans; they had high levels of aspartic acid, glutamic acid, threonine and serine, but there was no major difference in amino-acid composition between them. Carbohydrate analysis indicated typical components associated with sulphated glycoproteins, including fucose, galactose, glucose, mannose, N-acetylgalactosamine, N-acetylglucosamine and N-acetylneuraminic acid. Protein:carbohydrate ratios ranged from 0.1:1.0-3.5:1.0 and ester sulphate from 0.8 to 16.2 per cent. All fractions exhibited blood-group A reactivity and aggregated Streptococcus sanguis NCTC 7864; several fractions interacted similarly with Streptococcus mutans OMZ61.