The biosynthesis of L-arabinose in plants:: Molecular cloning and characterization of a Golgi-localized UDP-D-xylose 4-epimerase encoded by the MUR4 gene of Arabidopsis
The biosynthesis of L-arabinose in plants:: Molecular cloning and characterization of a Golgi-localized UDP-D-xylose 4-epimerase encoded by the MUR4 gene of Arabidopsis
复制标题
DOI：
10.1105/tpc.008425
复制
发表时间：
2003-02-01
期刊：
影响因子：
11.6
通讯作者：
Reiter, WD
中科院分区：
文献类型：
--
作者：
Burget, EG;Verma, R;Reiter, WD
拟南芥的mur 4突变体显示出在叶来源的细胞壁材料中单糖L-Ara减少50%，这是因为UDP-D-Xyl到UDP-L-Ara的4-差向异构化中的部分缺陷。为了确定潜在的mur 4表型的遗传病变，MUR 4基因被克隆的地图为基础的程序，并发现编码的II型膜蛋白的序列相似性的UDP-D-GIC 4-差向异构酶。在嗜甲基酵母巴斯德毕赤酵母中表达的MUR 4蛋白的酶测定表明，它催化UDP-D-Xyl到UDP-L-Ara的4-差向异构化，UDP-L-Ara是糖基转移酶在细胞壁多糖和壁驻留蛋白聚糖的阿拉伯糖基化中使用的核苷酸糖。MUR 4-绿色荧光蛋白构建体在拟南芥中的表达揭示了与靶向高尔基体一致的定位模式，表明MUR 4蛋白在阿拉伯糖基化细胞壁组分的生物合成中与糖基转移酶共定位。拟南芥基因组编码三种推定的蛋白质，与MUR 4具有> 76%的序列同一性，这可以解释为什么mur 4植物在UDP-L-Ara的从头合成中不完全缺陷。
The mur4 mutant of Arabidopsis shows a 50% reduction in the monosaccharide L-Ara in leaf-derived cell wall material because of a partial defect in the 4-epimerization of UDP-D-Xyl to UDP-L-Ara. To determine the genetic lesion underlying the mur4 phenotype, the MUR4 gene was cloned by a map-based procedure and found to encode a type-II membrane protein with sequence similarity to UDP-D-GIc 4-epimerases. Enzyme assays of MUR4 protein expressed in the methylotropic yeast Pichia pastoris indicate that it catalyzes the 4-epimerization of UDP-D-Xyl to UDP-L-Ara, the nucleotide sugar used by glycosyltransferases in the arabinosylation of cell wall polysaccharides and wall-resident proteoglycans. Expression of MUR4-green fluorescent protein constructs in Arabidopsis revealed localization patterns consistent with targeting to the Golgi, suggesting that the MUR4 protein colocalizes with glycosyltransferases in the biosynthesis of arabinosylated cell wall components. The Arabidopsis genome encodes three putative proteins with > 76% sequence identity to MUR4, which may explain why mur4 plants are not entirely deficient in the de novo synthesis of UDP-L-Ara.