Snider M D, Rogers O C
Cell. 1984 Mar;36(3):753-61. doi: 10.1016/0092-8674(84)90355-6.
The transport of sugar residues into the endoplasmic reticulum (ER) during glycoprotein synthesis was studied by examining the transmembrane orientations of the oligosaccharide-lipid precursors of asparagine-linked oligosaccharides. Using the lectin concanavalin A, the lipid-linked oligosaccharides Man3-5GlcNAc2 were found on the cytoplasmic side of ER-derived vesicles in vitro while lipid-linked Man6-9GlcNAc2 and Glc1-3Man9GlcNAc2 were found facing the lumen. These results suggest that Man5GlcNAc2-lipid is synthesized on the cytoplasmic side of the ER membrane and then translocated to the luminal side. Glc3Man9GlcNAc2-lipid is then completed on the luminal side where it serves as the donor in peptide glycosylation. Translocation of Man5GlcNAc2-lipid offers a mechanism for the export of sugar residues from the cytoplasm during glycoprotein synthesis. This translocation may be the reason for the participation of lipid-linked mono- and oligosaccharides in glycoprotein synthesis.
通过检测天冬酰胺连接型寡糖的寡糖-脂质前体的跨膜方向，研究了糖蛋白合成过程中糖残基向内质网（ER）的转运。使用凝集素伴刀豆球蛋白A，在体外发现脂质连接型寡糖Man3-5GlcNAc2存在于内质网衍生囊泡的胞质侧，而脂质连接型Man6-9GlcNAc2和Glc1-3Man9GlcNAc2则面向内腔。这些结果表明，Man5GlcNAc2-脂质在内质网膜的胞质侧合成，然后转运至腔侧。然后，Glc3Man9GlcNAc2-脂质在腔侧完成合成，并在肽糖基化过程中作为供体。Man5GlcNAc2-脂质的转运为糖蛋白合成过程中糖残基从细胞质输出提供了一种机制。这种转运可能是脂质连接型单糖和寡糖参与糖蛋白合成的原因。
