title: Does Rft1 flip an N-glycan lipid precursor?
abstract: Protein N-glycosylation requires flipping of the glycolipid Man(5)GlcNAc(2)-diphosphate dolichol (Man(5)GlcNAc(2)-PP-Dol) across the endoplasmic reticulum (ER). Helenius et al. report genetic evidence suggesting that Rft1, an essential ER membrane protein in yeast, is required directly to translocate Man(5)GlcNAc(2)-PP-Dol. We now show that a specific ER protein(s), but not Rft1, is required to flip Man(5)GlcNAc(2)-PP-Dol in reconstituted vesicles. Rft1 may have a critical accessory role in translocating Man(5)GlcNAc(2)-PP-Dol in vivo, but the Man(5)GlcNAc(2)-PP-Dol flippase itself remains to be identified.
authors.affiliation: Department of Biochemistry, Weill Cornell Medical College, New York, New York 10065, USA.
authors.forename: Christian G
authors.initials: CG
authors.lastname: Frank
authors.forename: Sumana
authors.initials: S
authors.lastname: Sanyal
authors.forename: Jeffrey S
authors.initials: JS
authors.lastname: Rush
authors.forename: Charles J
authors.initials: CJ
authors.lastname: Waechter
authors.forename: Anant K
authors.initials: AK
authors.lastname: Menon
mesh_terms: D004286:Dolichols / Q000031:analogs & derivatives* / Q000378:metabolism; D008351:Mannans / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000378:metabolism*; D026901:Membrane Transport Proteins; D049294:Phospholipid Transfer Proteins / Q000378:metabolism*; D015203:Reproducibility of Results; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*
chemical_list: D004286:Dolichols; C404956:Man(6)GlcNAc(2)-PP-dolichol; D008351:Mannans; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D049294:Phospholipid Transfer Proteins; C486728:RFT1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins