Transmembrane movement of dolichol linked carbohydrates during N-glycoprotein biosynthesis in the endoplasmic reticulum.
The process of N-linked glycosylation of secretory proteins is characterized by enzymatic reactions occurring on both sides of the endoplasmic reticulum (ER) membrane. On either side multiple glycosyltransferases participate in the stepwise addition of monosaccharides to core oligosaccharide unit that is attached to the lipid carrier dolichyl pyrophosphate. Cytoplasm-oriented glycosyltransferases use nucleotide-activated sugars as substrates, whereas lumen-oriented transferases that act later in the pathway make use of dolichyl phosphate-linked monosaccharides. The completely assembled core oligosaccharide is transferred to proteins on the lumenal side of the ER. The topological organization of this biosynthetic pathway requires the translocation of lipid-linked mono- and oligo-saccharides across the ER membrane. The transfer of the substrates and intermediates depend on specific translocators, i.e. so called flippases.
Institute of Microbiology, Swiss Federal Institute of Technology, Schmelzbergstr. 7, CH-8092 Zürich, Switzerland. helenius@micro.biol.ethz.ch
Jonne
J
Helenius
Markus
M
Aebi
D000595:Amino Acid Sequence; D000818:Animals; D001692:Biological Transport; D050260:Carbohydrate Metabolism; D002352:Carrier Proteins / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D004286:Dolichols / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D006023:Glycoproteins / Q000378:metabolism*; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism*; D008954:Models, Biological; D008969:Molecular Sequence Data; D009005:Monosaccharides / Q000378:metabolism; D049294:Phospholipid Transfer Proteins; D017386:Sequence Homology, Amino Acid
D002352:Carrier Proteins; D004286:Dolichols; D006023:Glycoproteins; D008565:Membrane Proteins; D009005:Monosaccharides; D049294:Phospholipid Transfer Proteins