Hochstenbach F, Klis F M, van den Ende H, van Donselaar E, Peters P J, Klausner R D
Cell Biology and Metabolism Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
Proc Natl Acad Sci U S A. 1998 Aug 4;95(16):9161-6. doi: 10.1073/pnas.95.16.9161.
The cell wall protects fungi against lysis and determines their cell shape. Alpha-glucan is a major carbohydrate component of the fungal cell wall, but its function is unknown and its synthase has remained elusive. Here, we describe a fission yeast gene, ags1(+), which encodes a putative alpha-glucan synthase. In contrast to the structure of other carbohydrate polymer synthases, the predicted Ags1 protein consists of two probable catalytic domains for alpha-glucan assembly, namely an intracellular domain for alpha-glucan synthesis and an extracellular domain speculated to cross-link or remodel alpha-glucan. In addition, the predicted Ags1 protein contains a multipass transmembrane domain that might contribute to transport of alpha-glucan across the membrane. Loss of Ags1p function in a temperature-sensitive mutant results in cell lysis, whereas mutant cells grown at the semipermissive temperature contain decreased levels of cell wall alpha-glucan and fail to maintain rod shapes, causing rounding of the cells. These findings demonstrate that alpha-glucan is essential for fission yeast morphogenesis.
细胞壁保护真菌免受裂解并决定其细胞形状。α-葡聚糖是真菌细胞壁的主要碳水化合物成分，但其功能尚不清楚，其合成酶也一直未被发现。在此，我们描述了一种裂殖酵母基因ags1(+)，它编码一种假定的α-葡聚糖合成酶。与其他碳水化合物聚合物合成酶的结构不同，预测的Ags1蛋白由两个可能用于α-葡聚糖组装的催化结构域组成，即一个用于α-葡聚糖合成的细胞内结构域和一个推测用于交联或重塑α-葡聚糖的细胞外结构域。此外，预测的Ags1蛋白含有一个多次跨膜结构域，可能有助于α-葡聚糖跨膜运输。温度敏感突变体中Ags1p功能的丧失导致细胞裂解，而在半允许温度下生长的突变细胞细胞壁α-葡聚糖水平降低，无法维持杆状形状，导致细胞变圆。这些发现表明α-葡聚糖对裂殖酵母形态发生至关重要。
