STRUCTURES OF SULFATED OLIGOSACCHARIDES IN HUMAN TRACHEA MUCIN GLYCOPROTEINS

The structures of high molecular weight sulfated oligosaccharide chain s in mucins purified from the sputum of a patient with cystic fibrosis and blood group H determinant were established. Reduced oligosacchari des released by treatment with alkaline borohydride were separated by ion exchange chromatography on DEAE-Agarose and a fraction containing multisulfated chains was further purified by lectin affinity chromatog raphy to completely remove small amounts of sialylated chains. A major sulfated oligosaccharide fraction containing chains with an average o f 160 to 200 sugar residues was isolated by gel filtration on BioGel P -10 columns and individual subfractions were characterized by methylat ion analysis, periodate oxidation and sequential glycosidase digestion before and after desulfation. Carbohydrate analysis yielded Fuc, Gal and GldNAc in a ratio of 1:2:2.1 and only one galactosaminitol residue for every 160-to 200 sugar residues. The average molecular weight of oligosaccharide chains in these fractions was between 27,000 and 40,00 0 daltons. Structural analysis showed that these high molecular weight chains contained varying amounts of the repeating unit shown in the f ollowing oligosaccharide. Only one in about every 10 repeating units c ontained sulfate esters. Several shorter chains which contain 2 to 3 s ulfate esters were also isolated from this multisulfated oligosacchari de fraction. The structures proposed for these oligosaccharides indica te that they are lower molecular weight chains with the same general s tructure as those found in the high molecular weight sulfated oligosac charides. [GRAPHICS] Taken collectively, the results of thes e studies show that a major sulfated oligosaccharide fraction in respo ratory mucin purified from the mucus of patients with cystic fibrosis contains high molecular weight branched chains that consist of a repea ting oligosaccharide sequence with sulfate linked to the 6 positions o f galactose and possibly GlcNAc residues in the side chains.