title: Eukaryotic N-glycosylation occurs via the membrane-anchored C-terminal domain of the Stt3p subunit of oligosaccharyltransferase.
abstract: N-glycosylation is an essential and highly conserved protein modification. In eukaryotes, it is catalyzed by a multisubunit membrane-associated enzyme, oligosaccharyltransferase (OT). We report the high resolution structure of the C-terminal domain of eukaryotic Stt3p. Unlike its soluble β-sheet-rich prokaryotic counterparts, our model reveals that the C-terminal domain of yeast Stt3p is highly helical and has an overall oblate spheroid-shaped structure containing a membrane-embedded region. Anchoring of this protein segment to the endoplasmic reticulum membrane is likely to bring the membrane-embedded donor substrate closer, thus facilitating glycosylation efficiency. Structural comparison of the region near the WWDYG signature motif revealed that the acceptor substrate-binding site of yeast OT strikingly resembles its prokaryotic counterparts, suggesting a conserved mechanism of N-glycosylation from prokaryotes to eukaryotes. Furthermore, comparison of the NMR and cryo-EM structures of yeast OT revealed that the molecular architecture of this acceptor substrate-recognizing domain has interesting spatial specificity for interactions with other essential OT subunits.
authors.affiliation: Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849, USA.
authors.forename: Chengdong
authors.initials: C
authors.lastname: Huang
authors.forename: Rajagopalan
authors.initials: R
authors.lastname: Bhaskaran
authors.forename: Smita
authors.initials: S
authors.lastname: Mohanty
mesh_terms: D020816:Amino Acid Motifs; D018360:Crystallography, X-Ray; D006031:Glycosylation; D006602:Hexosyltransferases / Q000737:chemistry* / Q000235:genetics; D006801:Humans; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000235:genetics
chemical_list: D008565:Membrane Proteins; D029701:Saccharomyces cerevisiae Proteins; D006602:Hexosyltransferases; C096554:STT3 protein, S cerevisiae