title: Glycopeptide specificity of the secretory protein folding sensor UDP-glucose glycoprotein:glucosyltransferase.
abstract: Secretory and membrane N-linked glycoproteins undergo folding and oligomeric assembly in the endoplasmic reticulum with the aid of a folding mechanism known as the calnexin cycle. UDP-glucose glycoprotein:glucosyltransferase (UGGT) is the sensor component of the calnexin cycle, which recognizes these glycoproteins when they are incompletely folded, and transfers a glucose residue from UDP-glucose to N-linked Man9-GlcNAc2 glycans. To determine how UGGT recognizes incompletely folded glycoproteins, we used purified enzyme to glucosylate a set of Man9-GlcNAc2 glycopeptide substrates in vitro, and determined quantitatively the glucose incorporation into each glycan by mass spectrometry. A ranked order of glycopeptide specificity was found that provides the criteria for the recognition of substrates by UGGT. The preference for amino-acid residues close to N-linked glycans provides criteria for the recognition of glycopeptide substrates by UGGT.
authors.affiliation: Biochemistry Department, Faculty of Medicine, McGill University, Montreal, Quebec, Canada.
authors.forename: Sean C
authors.initials: SC
authors.lastname: Taylor
authors.forename: Pierre
authors.initials: P
authors.lastname: Thibault
authors.forename: Daniel C
authors.initials: DC
authors.lastname: Tessier
authors.forename: John J M
authors.initials: JJ
authors.lastname: Bergeron
authors.forename: David Y
authors.initials: DY
authors.lastname: Thomas
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D005964:Glucosyltransferases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006020:Glycopeptides / Q000138:chemical synthesis / Q000737:chemistry*; D006023:Glycoproteins / Q000096:biosynthesis / Q000737:chemistry; D007700:Kinetics; D008969:Molecular Sequence Data; D017510:Protein Folding; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology
chemical_list: D006020:Glycopeptides; D006023:Glycoproteins; D011994:Recombinant Proteins; D005964:Glucosyltransferases; C072423:mannosylglycoprotein 1,3-glucosyltransferase