Structures of N-glycans of a ricin-resistant mutant of baby hamster kidney cells. Synthesis of high-mannose and hybrid N-glycans.
The asparagine-linked glycopeptides (N-glycans) of a ricin-resistant mutant of baby hamster kidney (BHK) cells, RicR21, have been isolated and fractionated from a Pronase digest of disrupted cells by concanavalin A (Con A)-Sepharose chromatography, ion-exchange chromatography, and lentil lectin chromatography. The structures of all the major N-glycans have been determined by 500-MHz H NMR spectroscopy. RicR21 synthesizes only hybrid and high-mannose N-glycans. All the hybrid structures contain only three mannose residues. The major hybrid glycopeptide has the following structure: (Formula: see text). There is also about 15% of the nonfucosylated species present. Only a small amount (less than or equal to 5%) of the asialo hybrid is produced. Branched hybrid N-glycans are also present in RicR21 cells, containing two complex antenna linked beta 1----2 and beta 1----4 to the Man alpha 1----3 arm; about 70% of this species is core fucosylated. Man6GlcNAc2 glycopeptide is the most abundant (about 70%) of the high-mannose N-glycans. These studies account for the very poor ricin binding property of this mutant, as the sialic acid residues of the major hybrid N-glycan are exclusively linked alpha 2----3 to galactose and ricin is unable to bind to alpha 2----3-substituted galactosyl residues [Baenziger, J. U., & Fiete, D. (1979) J. Biol. Chem. 254, 9795-9799].
D000818:Animals; D002240:Carbohydrate Sequence; D002460:Cell Line; D003208:Concanavalin A; D006224:Cricetinae; D004351:Drug Resistance; D006020:Glycopeptides / Q000032:analysis; D006023:Glycoproteins / Q000096:biosynthesis / Q000235:genetics*; D006026:Glycoside Hydrolases; D007668:Kidney; D009682:Magnetic Resonance Spectroscopy; D009154:Mutation; D012276:Ricin / Q000633:toxicity*
D006020:Glycopeptides; D006023:Glycoproteins; D003208:Concanavalin A; D012276:Ricin; D006026:Glycoside Hydrolases