title: Distinct orders of GalNAc incorporation into a peptide with consecutive threonines.
abstract: Mucin O-glycosylation is initiated by a transfer of N-acetyl-d-galactosamine (GalNAc) to Ser and Thr residues in polypeptides with a family of UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferases (pp-GalNAc-Ts). In this paper, four human pp-GalNAc-Ts (pp-GalNAc-T1, T2, T3, and T4) were tested for their preferential orders of GalNAc incorporation into FITC-PTTTPITTTTK, a portion of the tandem repeat of human MUC2. The products were separated by reverse-phase HPLC and characterized by MALDI-TOF MS and peptide sequencing. pp-GalNAc-T1 showed preference for acceptor sites, but the order of the incorporation into these sites seemed to be random. In contrast, the GalNAc incorporation by pp-GalNAc-T2, T3, or T4 was not only site-specific but also according to the specific orders. Furthermore, pp-GalNAc-T2, T3, or T4 had distinct maximum numbers of GalNAc incorporations into this peptide.
authors.affiliation: Laboratory of Cancer Biology and Molecular Immunology, Graduate School of Pharmaceutical Sciences, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Kato
authors.forename: H
authors.initials: H
authors.lastname: Takeuchi
authors.forename: N
authors.initials: N
authors.lastname: Miyahara
authors.forename: A
authors.initials: A
authors.lastname: Kanoh
authors.forename: H
authors.initials: H
authors.lastname: Hassan
authors.forename: H
authors.initials: H
authors.lastname: Clausen
authors.forename: T
authors.initials: T
authors.lastname: Irimura
mesh_terms: D000116:Acetylgalactosamine / Q000737:chemistry*; D016650:Fluorescein-5-isothiocyanate / Q000737:chemistry; D006031:Glycosylation; D055262:Mucin-2; D009077:Mucins / Q000737:chemistry*; D010455:Peptides / Q000737:chemistry; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods; D013912:Threonine / Q000737:chemistry
chemical_list: C524625:MUC2 protein, human; D055262:Mucin-2; D009077:Mucins; D010455:Peptides; D013912:Threonine; D016650:Fluorescein-5-isothiocyanate; D000116:Acetylgalactosamine