Tanner W, Lehle L
Biochim Biophys Acta. 1987 Apr 27;906(1):81-99. doi: 10.1016/0304-4157(87)90006-2.
S. cerevisiae contains many mannose-rich glycoproteins that possess N- and O-linked carbohydrate chains, and both types may even occur on one and the same protein. The steps in the synthesis of asparagine-linked chains begin with assembly and transfer of the lipid-linked precursor to protein in a way common to all eucaryotes. Subsequent modifications lead to mannosyl extensions of various lengths, but complex type carbohydrate structures are not formed. Oligosaccharides O-linked to serine/threonine consist exclusively of mannose in S. cerevisiae. The mannose residue attached directly to the protein is transferred from Dol-P-Man in a unique way, which has been observed so far for fungal cells only. The cellular localization of the glycosylation reactions is summarized and the problem of transmembrane translocation of the sugar precursors at the ER and the Golgi is discussed. Some aspects of secretory (sec) and asparagine linked glycosylation (alg) mutants have been covered, and the various hypotheses related to the possible functions of this costly protein modification process are discussed. The article may also be helpful for those, who want to exploit the yeast's protein synthesizing machinery by genetically manipulating the cells.
酿酒酵母含有许多富含甘露糖的糖蛋白，这些糖蛋白具有N-连接和O-连接的碳水化合物链，甚至这两种类型的链可能出现在同一种蛋白质上。天冬酰胺连接链的合成步骤始于脂质连接前体的组装和转移，其方式与所有真核生物相同，是将脂质连接前体转移到蛋白质上。随后的修饰导致不同长度的甘露糖基延伸，但不会形成复杂型碳水化合物结构。在酿酒酵母中，与丝氨酸/苏氨酸O-连接的寡糖仅由甘露糖组成。直接连接到蛋白质上的甘露糖残基以一种独特的方式从Dol-P-Man转移，这种方式迄今为止仅在真菌细胞中观察到。本文总结了糖基化反应的细胞定位，并讨论了糖前体在ER和高尔基体的跨膜转运问题。文章还涵盖了分泌（sec）和天冬酰胺连接糖基化（alg）突变体的一些方面，并讨论了与这种昂贵的蛋白质修饰过程可能功能相关的各种假设。对于那些想通过基因操作细胞来利用酵母蛋白质合成机制的人来说，本文可能也会有所帮助。
