Hybrid sialylated N-glycans are minor constituents of normal BHK-cell glycoproteins and a prominent feature in glycoproteins of some ricin-resistant cell lines.

Baby-hamster kidney (BHK) cells were labelled metabolically by growth in media containing radioactive sugars and the asparagine-linked glycopeptides (N-glycans) obtained by Pronase digestion of disrupted cells were fractionated by chromatography on concanavalin A-Sepharose. About 2-3% of the total [3H]galactose- or [3H]fucose-labelled glycopeptides were found to be bound tightly to the lectin column and were eluted with 500 mM-methyl alpha-mannoside. Further analysis of these minor components by chromatography on Bio-Gel P4, lentil-lectin-Sepharose and DEAE-Sephacel and sensitivity to alpha-mannosidase indicates the presence in BHK-cell glycopeptides of hybrid structures of the following form: (Formula: see text) Similar structures were identified as major features of the glycoproteins of ricin-resistant mutants RicR17 and RicR19 as described previously for RicR21 cells [Hughes, Mills & Stojanovic (1983) Carbohydr. Res. 120, 215-234]. The RicR15 cell line also produces significant amounts of hybrid N-glycans. The studies show that the novel N-glycans accumulating in ricin-resistant mutants are derived by a metabolic pathway that exists to a minor extent in normal BHK cells.