A search for hyperglycosylation signals in yeast glycoproteins
A search for hyperglycosylation signals in yeast glycoproteins
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DOI：
10.1074/jbc.m406678200
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发表时间：
2004-10-15
影响因子：
4.8
通讯作者：
Larriba, G
中科院分区：
文献类型：
--
作者：
Conde, R;Cueva, R;Larriba, G
酿酒酵母糖蛋白的N -寡糖分为核心型和甘露聚糖型。前者含有13 - 14个甘露糖，而甘露聚糖型结构由一个内核和一条多达200 - 300个甘露糖的外链组成，这一过程被称为高糖基化。高糖基化底物的选择带来了一个理论和实践问题。为了确定高糖基化的决定因素，我们以主要外切葡聚糖酶为模型，分析了序列子中第二个氨基酸（Xaa）在这一过程中的影响。我们的结果表明，带负电荷的氨基酸抑制高糖基化，而带正电荷的氨基酸则促进高糖基化。基于Exg1的三维结构，我们提出Xaa影响内核的取向，使其在适合添加α - 1,6 -甘露糖的位置可被甘露聚糖聚合酶I作用。天然外切葡聚糖酶第二个序列子的Xaa中存在Glu，这表明负选择可能驱动这些位点的进化。然而，对酿酒酵母和异常毕赤酵母分泌的转化酶的比较表明，高糖基化信号也受到正选择。
N-oligosaccharides of Saccharomyces cerevisiae glycoproteins are classified as core and mannan types. The former contain 13-14 mannoses whereas mannan-type structures consist of an inner core extended with an outer chain of up to 200-300 mannoses, a process known as hyperglycosylation. The selection of substrates for hyperglycosylation poses a theoretical and practical question. To identify hyperglycosylation determinants, we have analyzed the influence of the second amino acid (Xaa) of the sequon in this process using the major exoglucanase as a model. Our results indicate that negatively charged amino acids inhibit hyperglycosylation, whereas positively charged counterparts promote it. On the basis of the tridimensional structure of Exg1, we propose that Xaa influences the orientation of the inner core making it accessible to mannan polymerase I in the appropriate position for the addition of alpha-1,6-mannoses. The presence of Glu in the Xaa of the second sequon of the native exoglucanase suggests that negative selection may drive evolution of these sites. However, a comparison of invertases secreted by S. cerevisiae and Pichia anomala suggests that hyperglycosylation signals are also subjected to positive selection.