Yeast Kre1p is GPI-anchored and involved in both cell wall assembly and architecture
Yeast Kre1p is GPI-anchored and involved in both cell wall assembly and architecture
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DOI：
10.1099/mic.0.27175-0
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发表时间：
2004-10-01
期刊：
影响因子：
2.8
通讯作者：
Schmitt, MJ
中科院分区：
文献类型：
--
作者：
Breinig, F;Schleinkofer, K;Schmitt, MJ
Kre1p是一种参与酵母1,6-葡聚糖形成后期的细胞表面o糖蛋白。KRE1的破坏导致细胞壁总1,6-葡聚糖含量减少40%。本文表明，在酵母Deltakre1零突变体中，n端截断的Kre1p和缺乏c端糖基磷空间肌醇（GPI）附着位点的Kre1p变体都不能实现葡聚糖组装的正常功能，而全长Kre1p完全补充了Deltakre1零突变，并将细胞壁1,6-葡聚糖含量恢复到野生型水平。在酵母gpi1突变体中，一种绿色荧光蛋白标记的Kre1p衍生物被分泌到培养基中，这表明Kre1p在酵母分泌途径中加工过程中至少存在短暂的gpi锚定阶段。与细胞壁β - d -葡聚糖的严重缺陷相反，在Deltakre1破坏物中，细胞壁甘露蛋白的数量并没有显著减少，这一点可以通过研究毒素与分离细胞壁甘露蛋白的结合在竞争分析中得到证实。由于酵母Deltakre1突变体对zygocin和K28的敏感性不同，这两种杀伤病毒蛋白毒素使用不同的细胞壁甘露蛋白群体作为主要毒素受体，因此可以得出结论，在酵母Deltakre1背景下，甘露蛋白的总量与Kre1（+）野生型没有显著差异，而是在细胞表面的表达和分布上有显著差异。综上所述，这些数据支持并表明Kre1p在酵母细胞壁组装中的结构功能，而不是酶功能。
Kre1p is a cell surface O-glycoprotein involved in a late stage of 1,6-beta-glucan formation in the yeast Saccharomyces cerevisiae. Disruption of KRE1 leads to a 40% reduction in the overall 1,6-beta-glucan content of the cell wall. This paper shows that in a yeast Deltakre1 null mutant, neither an N-terminal-truncated Kre1p nor Kre1p variants lacking a C-terminal glycosylphospatidylinositol (GPI) attachment site are capable of achieving normal function in glucan assembly, while full-length Kre1p completely complements a Deltakre1 null mutation and restores cell wall 1,6-beta-glucan content up to wild-type level. In a yeast gpi1 mutant, a green-fluorescent-protein-tagged Kre1p derivative is secreted into the medium, indicating an at least transient GPI-anchoring stage of Kre1p during its processing within the yeast secretory pathway. In contrast to the severe defect in cell wall beta-D-glucan, the amount of cell wall mannoproteins is not significantly decreased in a Deltakre1 disruptant, as could be confirmed in competition assays by investigating toxin binding to isolated cell wall mannoproteins. Since the yeast Deltakre1 mutant differed in its sensitivity to zygocin and K28, two killer viral protein toxins that use different cell wall mannoprotein populations as a primary toxin receptor, it can be concluded that in a yeast Deltakre1 background, mannoproteins do not differ significantly in total amount from a Kre1(+) wild-type but rather in their expression and distribution at the cell surface. Taken together, these data favour and suggest a structural, rather than enzymic, function of Kre1p in yeast cell wall assembly.