title: Conformational studies on the MUC1 tandem repeat glycopeptides: implication for the enzymatic O-glycosylation of the mucin protein core.
abstract: The tandem repeat of the MUC1 protein core is a major site of O-glycosylation that is catalyzed by several polypeptide GalNAc-transferases. To define structural features of the peptide substrates that contribute to acceptor substrate efficiency, solution structures of the 21-residue peptide AHGVTSAPDTRPAPGSTAPPA (AHG21) from the MUC1 protein core and four isoforms, glycosylated with alpha-N-acetylgalactosamine on corresponding Thr residues, AHG21 (T5), AHG21 (T10), AHG21 (T17), and AHG21 (T5,T17), were investigated by NMR spectroscopy and computational methods. NMR studies revealed that sugar attachment affected the conformational equilibrium of the peptide backbone near the glycosylated Thr residues. The clustering of the low-energy conformations for nonglycosylated and glycosylated counterparts within the VTSA, DTR, and GSTA fragments (including all sites of potential glycosylation catalyzed by GalNAc-T1, -T2, and -T4 transferases) showed that the glycosylated peptides display distinct structural propensities that may explain, in part, the differences in substrate specificities exhibited by these polypeptide GalNAc-transferases.
authors.affiliation: Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE 68198-6805, USA.
authors.forename: Leo
authors.initials: L
authors.lastname: Kinarsky
authors.forename: Ganesh
authors.initials: G
authors.lastname: Suryanarayanan
authors.forename: Om
authors.initials: O
authors.lastname: Prakash
authors.forename: Hans
authors.initials: H
authors.lastname: Paulsen
authors.forename: Henrik
authors.initials: H
authors.lastname: Clausen
authors.forename: Franz-Georg
authors.initials: FG
authors.lastname: Hanisch
authors.forename: Michael A
authors.initials: MA
authors.lastname: Hollingsworth
authors.forename: Simon
authors.initials: S
authors.lastname: Sherman
mesh_terms: D000595:Amino Acid Sequence; D002384:Catalysis; D006020:Glycopeptides / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism; D006031:Glycosylation; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009077:Mucins / Q000737:chemistry* / Q000378:metabolism; D017350:N-Acetylgalactosaminyltransferases / Q000737:chemistry / Q000378:metabolism; D019906:Nuclear Magnetic Resonance, Biomolecular; D011487:Protein Conformation; D020449:Repetitive Sequences, Amino Acid; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D000097763:Polypeptide N-acetylgalactosaminyltransferase
chemical_list: D006020:Glycopeptides; D009077:Mucins; D017350:N-Acetylgalactosaminyltransferases; D000097763:Polypeptide N-acetylgalactosaminyltransferase