Esmon B, Esmon P C, Schekman R
J Biol Chem. 1984 Aug 25;259(16):10322-7.
N-linked oligosaccharides have been examined on glycoproteins accumulated in yeast mutants that are blocked at successive stages in the secretory pathway, and in a new mutant, gls1-1, deficient in removal of glucose from N-linked core oligosaccharides, but not blocked in secretion. Oligosaccharides on invertase, a secreted protein, and carboxypeptidase Y, a vacuolar protein, are matured normally in the gls1 mutant but retain three glucoses/carbohydrate chain. The gls1 mutation is recessive and extracts of mutant cells are inactive in release of labeled glucose from core oligosaccharides. The mutant thus lacks glucosidase I activity but could also be deficient in the other core oligosaccharide glucosidase. When transport from the endoplasmic reticulum is blocked in sec18, N-linked oligosaccharides accumulate with a size corresponding to Man8GlcNAc2 when the normal GLS1 allele is present, and Glc3Man8GlcNAc2 in the gls1 mutant. From this we infer that all glucose units are removed prior to glycoprotein transport from the endoplasmic reticulum.
已对在分泌途径中连续阶段受阻的酵母突变体以及一个新的突变体gls1-1中积累的糖蛋白上的N-连接寡糖进行了研究。在新突变体gls1-1中，N-连接核心寡糖的葡萄糖去除存在缺陷，但分泌未受阻。分泌蛋白转化酶和液泡蛋白羧肽酶Y上的寡糖在gls1突变体中正常成熟，但每个碳水化合物链保留三个葡萄糖。gls1突变是隐性的，突变细胞提取物在从核心寡糖释放标记葡萄糖方面无活性。因此，该突变体缺乏葡糖苷酶I活性，但也可能缺乏其他核心寡糖葡糖苷酶。当在sec18中内质网运输受阻时，存在正常GLS1等位基因时，N-连接寡糖积累的大小对应于Man8GlcNAc2，而在gls1突变体中为Glc3Man8GlcNAc2。由此我们推断，在糖蛋白从内质网运输之前，所有葡萄糖单位都已被去除。
