Mucin-type glycoprotein from Drosophila melanogaster embryonic cells: characterization of carbohydrate component.

A secreted glycoprotein (GP) with apparent molecular mass of 90 kDa produced by cultured embryonic cells of Drosophila melanogaster was isolated and partially characterized. GP is enriched by Ser + Thr and Pro residues that constitute up to 30% of the total number of amino acids. An abundant carbohydrate moiety (40% of molecular mass) is mainly represented by vertebrate mucin-type O-linked disaccharide units Gal(beta 1-3)-GalNAc, occupying about a half of the total number of Ser+Thr residues and rendering the GP molecule high resistance to protease action. A few of N-glycans are also present in GP. These characteristics allow to consider the Drosophila GP (termed 'mucin-D') as a first representative of invertebrate mucin-type glycoproteins.