GLYCOPROTEIN FROM CULTURED DROSOPHILA-MELANOGASTER CELLS CONTAINS O-LINKED GAL(BETA-1-3)GALNAC CARBOHYDRATE UNITS

A mucin-type glycoprotein (GP) from Drosophila melanogaster cultured c ells which is also found in various insect tissues as a component of t he extracellular matrix is described. Mucin-type glycoproteins have no t been previously found in invertebrates. The GP has apparent molecula r mass similar to 90 kD and contains similar to 40% carbohydrate, main ly as N-acetylgalactosamine (GalNAc) and galactose (Gal), The amino ac ids Thr Ser, Pro, and Gly constitute the bulk of the protein component of the GP. Alkaline reduction of the GP with NaOH/NaBH4 or its digest ion with O-glycanase (endo-alpha-N-acetylgalactosaminidase) releases a n oligosaccharide component consisting mainly of the disaccharide gala ctosyl-beta 1,3-N-acetylgalactosamine (Gal(beta 1-3)GalNAc). Calculati ons show that approximately half of the Thr and Ser residues of the GP are attached to disaccharide by O-glycosidic bonds.