title: Determination of attachment sites for N-linked carbohydrate groups of class II histocompatibility alpha-chain and analysis of possible O-linked glycosylation of alpha- and gamma-chains.
abstract: Two glycopeptide fractions were isolated from a tryptic digest of the human class II antigen alpha-subunit, by chromatography on Lens culinaris and Ricinus communis lectin columns, respectively. Partial NH2-terminal sequence analysis of radiochemically labelled glycopeptide fractions allowed alignment with two stretches of the deduced DR alpha sequence, each encompassing a signal for N-linked glycosylation, i.e. Asn-X-Thr(Ser). The fraction displaying affinity for L. culinaris lectin was susceptible to the action of endo-beta-N-acetylglucosaminidase H whereas the fraction adsorbed to R. communis was not. Since DR alpha is known to carry only one N-linked carbohydrate chain in the high-mannose form, this glycan could thereby be mapped to Asn 78. Accordingly, the complex N-linked carbohydrate is attached to Asn 118. Moreover, analysis of material released from class II antigens and gamma-chains upon mild alkaline hydrolysis, indicates the presence of O-linked sugars on the alpha- and gamma- but not the beta-subunits.
authors.forename: L
authors.initials: L
authors.lastname: Claesson-Welsh
authors.forename: H
authors.initials: H
authors.lastname: Ploegh
authors.forename: P A
authors.initials: PA
authors.lastname: Peterson
mesh_terms: D000595:Amino Acid Sequence; D055598:Chemical Phenomena; D002621:Chemistry; D002846:Chromatography, Affinity; D004591:Electrophoresis, Polyacrylamide Gel; D006020:Glycopeptides / Q000032:analysis / Q000302:isolation & purification*; D000949:Histocompatibility Antigens Class II; D006801:Humans; D014357:Trypsin
chemical_list: D006020:Glycopeptides; D000949:Histocompatibility Antigens Class II; D014357:Trypsin