The EXT1/EXT2 tumor suppressors: catalytic activities and role in heparan sulfate biosynthesis
The EXT1/EXT2 tumor suppressors: catalytic activities and role in heparan sulfate biosynthesis
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DOI：
10.1093/embo-reports/kvd045
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发表时间：
2000-09-01
期刊：
影响因子：
7.7
通讯作者：
Kusche-Gullberg, M
中科院分区：
文献类型：
--
作者：
Senay, C;Lind, T;Kusche-Gullberg, M
硫酸乙酰肝素生物合成中的D-葡糖醛酸转移酶和N-乙酰-D-葡糖胺基转移酶反应与两个基因EXT 1和EXT 2相关，这两个基因也与遗传性骨疾病多发性外生骨疣有关。由于用于表达重组EXT蛋白的细胞系统合成内源性硫酸乙酰肝素，并且EXT蛋白倾向于缔合，因此不可能定义单个蛋白种类的功能作用。因此，我们在不合成硫酸乙酰肝素的酵母中表达了EXT 1和EXT 2。发现重组EXT 1和EXT 2在体外都催化两种糖基转移酶反应。这两种蛋白质的共表达，但不混合单独表达的重组EXT 1和EXT 2，在酵母和哺乳动物细胞中产生异源寡聚复合物，具有增强的糖基转移酶活性。这种刺激不依赖于蛋白质的膜结合状态。
The D-glucuronyltransferase and N-acetyl-D-glucosaminyl-transferase reactions in heparan sulfate biosynthesis have been associated with two genes, EXT1 and EXT2, which are also implicated in the inherited bone disorder, multiple exostoses. Since the cell systems used to express recombinant EXT proteins synthesize endogenous heparan sulfate, and the EXT proteins tend to associate, it has not been possible to define the functional roles of the individual protein species. We therefore expressed EXT1 and EXT2 in yeast, which does not synthesize heparan sulfate. The recombinant EXT1 and EXT2 were both found to catalyze both glycosyltransferase reactions in vitro. Coexpression of the two proteins, but not mixing of separately expressed recombinant EXT1 and EXT2, yields hetero-oligomeric complexes in yeast and mammalian cells, with augmented glycosyltransferase activities. This stimulation does not depend on the membrane-bound state of the proteins.