title: An N-acetylglucosaminyltransferase of the Golgi apparatus of the yeast Saccharomyces cerevisiae that can modify N-linked glycans.
abstract: The yeast Saccharomyces cerevisiae is widely regarded as being only capable of producing N-linked glycans with high-mannose structures. To investigate the glycan structures made in different mutant strains, we made use of a reporter protein consisting of a version of hen egg lysozyme that contains a single site for N-linked glycosylation. Mass spectrometry analysis of the attached glycans revealed that a large proportion contained an unexpected extra mass corresponding to a single N-acetylhexosamine residue. In addition, the glycosylated lysozyme was recognized by an N-acetylglucosamine specific lectin. The genome of S. cerevisiae contains an uncharacterized open reading frame, YOR320c, that is related to a known N-acetylglucosaminyltransferase. Deletion of this ORF resulted in the disappearance of the extra mass on the N-linked glycans and loss of lectin binding. We show that the protein encoded by YOR320c (which we term Gnt1p) is localized to the Golgi apparatus and has GlcNAc-transferase activity in vitro. The physiological role of Gnt1p is unclear because mutants lacking the protein show no obvious growth or cell wall defects. Nonetheless, these results indicate that heterologous glycoproteins expressed in yeast can receive N-glycans with structures other than high mannose. In addition, they indicate that the lumen of the yeast Golgi contains UDP-GlcNAc, which may facilitate reconstitution of higher eukaryotic N-glycan processing.
authors.affiliation: MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK.
authors.forename: Takehiko
authors.initials: T
authors.lastname: Yoko-o
authors.forename: Christine A R
authors.initials: CA
authors.lastname: Wiggins
authors.forename: Jürgen
authors.initials: J
authors.lastname: Stolz
authors.forename: Sew Y
authors.initials: SY
authors.lastname: Peak-Chew
authors.forename: Sean
authors.initials: S
authors.lastname: Munro
mesh_terms: D000595:Amino Acid Sequence; D017353:Gene Deletion; D006031:Glycosylation; D006056:Golgi Apparatus / Q000201:enzymology* / Q000378:metabolism; D013058:Mass Spectrometry; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism; D008969:Molecular Sequence Data; D009113:Muramidase / Q000737:chemistry / Q000378:metabolism; D017351:N-Acetylglucosaminyltransferases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016366:Open Reading Frames / Q000235:genetics; D011134:Polysaccharides / Q000737:chemistry / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: D008565:Membrane Proteins; D011134:Polysaccharides; D029701:Saccharomyces cerevisiae Proteins; D017351:N-Acetylglucosaminyltransferases; D009113:Muramidase