Gentzsch M, Tanner W
Lehrstuhl für Zellbiologie und Pflanzenphysiologie, Universität Regensburg, Germany.
EMBO J. 1996 Nov 1;15(21):5752-9.
The transfer of mannose to seryl and threonyl residues of secretory proteins is catalyzed by a family of protein mannosyltransferases coded for by seven genes (PMT1-7). Mannose dolichylphosphate is the sugar donor of the reaction, which is localized at the endoplasmic reticulum. By gene disruption and crosses all single, double and triple mutants of genes PMT1-4 were constructed. Two of the double and three of the triple mutants were not able to grow under normal conditions; three of these mutants could grow, however, when osmotically stabilized. The various mutants were extensively characterized concerning growth, morphology and their sensitivity to killer toxin K1, caffeine and calcofluor white. O-Mannosylation of gp115/Gas1p was affected only in pmt4 mutants, whereas glycosylation of chitinase was mainly affected in pmt1 and pmt2 mutants. The results show that protein O-glycosylation is essential for cell wall rigidity and cell integrity and that this protein modification, therefore, is vital for Saccharomyces cerevisiae.
甘露糖向分泌蛋白的丝氨酰和苏氨酰残基的转移由一个由七个基因（PMT1 - 7）编码的蛋白质甘露糖基转移酶家族催化。磷酸多萜醇甘露糖是该反应的糖供体，其定位于内质网。通过基因破坏和杂交构建了基因PMT1 - 4的所有单突变体、双突变体和三突变体。其中两个双突变体和三个三突变体在正常条件下无法生长；然而，当进行渗透稳定处理时，这些突变体中的三个能够生长。对各种突变体在生长、形态以及它们对杀伤毒素K1、咖啡因和荧光增白剂的敏感性方面进行了广泛表征。gp115 / Gas1p的O - 甘露糖基化仅在pmt4突变体中受到影响，而几丁质酶的糖基化主要在pmt1和pmt2突变体中受到影响。结果表明，蛋白质O - 糖基化对于细胞壁刚性和细胞完整性至关重要，因此这种蛋白质修饰对于酿酒酵母至关重要。
