title: Presence of asparagine-linked N-acetylglucosamine and chitobiose in Pyrus pyrifolia S-RNases associated with gametophytic self-incompatibility.
abstract: S-RNases encoded by the S-locus of rosaceous and solanaceous plants discriminate between the S-alleles of pollen in gametophytic self-incompatibility reactions, but it is not clear how. We report the structures of N-glycans attached to each of the N-glycosylation sites of seven S-RNases in Pyrus pyrifolia of the Rosaceae. The structures were identified by chromatographic analysis of pyridylaminated sugar chains prepared from S4-RNase and by liquid chromatography/electrospray ionization-mass spectrometric analysis of the protease digests of reduced and S-carboxymethylated S-RNases. S4-RNase carries various types of sugar chains, including plant-specific ones with beta1-->2-linked xylose and alpha1-->3-linked fucose residues. More than 70% of the total N-glycans of S4-RNase are, however, an N-acetylglucosamine or a chitobiose (GlcNAcbeta1-->4GlcNAc), which has not been found naturally. The N-acetylglucosamine and chitobiose are mainly present at the N-glycosylation sites within the putative recognition sites of the S-RNase, suggesting that these sugar chains may interact with pollen S-product(s).
authors.affiliation: Division of Protein Chemistry, Institute for Protein Research, Osaka University, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Ishimizu
authors.forename: Y
authors.initials: Y
authors.lastname: Mitsukami
authors.forename: T
authors.initials: T
authors.lastname: Shinkawa
authors.forename: S
authors.initials: S
authors.lastname: Natsuka
authors.forename: S
authors.initials: S
authors.lastname: Hase
authors.forename: M
authors.initials: M
authors.lastname: Miyagi
authors.forename: F
authors.initials: F
authors.lastname: Sakiyama
authors.forename: S
authors.initials: S
authors.lastname: Norioka
mesh_terms: D000117:Acetylglucosamine / Q000032:analysis*; D000595:Amino Acid Sequence; D001216:Asparagine / Q000032:analysis*; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D002851:Chromatography, High Pressure Liquid; D004187:Disaccharides / Q000032:analysis*; D006023:Glycoproteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000737:chemistry* / Q000302:isolation & purification; D012260:Ribonucleases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D014197:Trees / Q000201:enzymology* / Q000235:genetics
chemical_list: D004187:Disaccharides; D006023:Glycoproteins; D009844:Oligosaccharides; C032438:chitobiose; D001216:Asparagine; D012260:Ribonucleases; C022542:ribonuclease S; D000117:Acetylglucosamine