2.A.66.3.2
Endoplasmic reticular RFT1 protein, a Man(5)GlcNAc(2)-PP-dolichol translocation protein of 541 aas and 12 TMSs in a 6 + 6 TMS arrangement.  It is probably an ntramembrane glycolipid transporter that operates in the biosynthetic pathway of dolichol-linked oligosaccharides, the glycan precursors employed in protein asparagine (N)-glycosylation. The sequential addition of sugars to dolichol pyrophosphate produces dolichol-linked oligosaccharides containing up to fourteen sugars, including two GlcNAcs, nine mannoses and three glucoses. Once assembled, the oligosaccharide is transferred from the lipid to nascent proteins by oligosaccharyltransferases. The assembly of dolichol-linked oligosaccharides begins on the cytosolic side of the endoplasmic reticulum membrane and finishes in its lumen. RFT1 could mediate the translocation of the cytosolically oriented intermediate DolPP-GlcNAc2Man5, produced by ALG11, into the ER lumen where dolichol-linked oligosaccharides assembly continues (Haeuptle et al. 2008, Vleugels et al. 2009). Rft1 is associated with congenital disorder of glycosylation, RFT1-CDG (Hirata et al. 2024).