Tanner W, Haselbeck A, Schwaiger H, Lehle L
Philos Trans R Soc Lond B Biol Sci. 1982 Dec 24;300(1099):185-94. doi: 10.1098/rstb.1982.0165.
The pathways for protein N- and O-glycosylation in yeast cells are summarized. Evidence is presented that the terminal glucosyl residues of the dolichyl-PP-oligosaccharide intermediate are responsible for decreasing the Km for the peptide to be N-glycosylated. A liposomal model system is introduced that allows the study of a dolichyl phosphate (Dol-P) dependent transmembrane transport of mannosyl residues. The results obtained so far suggest that the mannosylation of Dol-P and the transmembrane translocation of Dol-P-Man are catalysed by the enzyme more or less simultaneously. However, only about 8-10% of the enzyme molecules incorporated into the liposomes seem to carry out the 'coupled' reaction. The glycosylation of carboxypeptidase Y is not required for this protein to reach the vacuole, its target organelle. In the presence of low concentrations of tunicamycin, however, yeast cells do stop growth. This does not seem to be due to the inhibition of secretion of glycoproteins like external invertase. It is postulated that protein glycosylation is crucial for a cell cycle event during the G1 phase.
总结了酵母细胞中蛋白质N-糖基化和O-糖基化的途径。有证据表明，多萜醇焦磷酸寡糖中间体的末端葡萄糖基残基负责降低待N-糖基化肽的Km值。引入了一种脂质体模型系统，该系统可用于研究磷酸多萜醇（Dol-P）依赖性的甘露糖基残基跨膜转运。目前获得的结果表明，Dol-P的甘露糖基化和Dol-P-Man的跨膜转运或多或少是由该酶同时催化的。然而，掺入脂质体中的酶分子似乎只有约8-10%进行“偶联”反应。羧肽酶Y的糖基化对于该蛋白质到达其靶细胞器液泡并非必需。然而，在低浓度衣霉素存在下，酵母细胞确实会停止生长。这似乎不是由于抑制了如外切转化酶等糖蛋白的分泌。据推测，蛋白质糖基化对于G1期的细胞周期事件至关重要。
