Structural Characterization of Arabidopsis Leaf Arabinogalactan Polysaccharides
Structural Characterization of Arabidopsis Leaf Arabinogalactan Polysaccharides
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DOI：
10.1104/pp.112.202309
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发表时间：
2012-10-01
期刊：
影响因子：
7.4
通讯作者：
Dupree, Paul
中科院分区：
文献类型：
--
作者：
Tryfona, Theodora;Liang, Hui-Chung;Dupree, Paul
阿拉伯半乳糖(AG)修饰的蛋白质在细胞壁结构和植物发育中具有重要作用，但对这种多糖的结构和生物合成知之甚少。为了便于生物合成突变体的分析，从拟南芥(Arabiopsis Thaliana)植物的叶片中分离出水提阿拉伯半乳糖蛋白(AGPs)，并对其糖组分的结构进行了研究。利用能够专一性地降解AG的酶来释放AG寡糖。用高能基质辅助激光解吸、电离碰撞诱导解离质谱法和糖凝胶电泳法对释放的低聚糖进行了表征。拟南芥AG是由带有β-(1->；6)-D-半乳糖侧链的β-(1->；3)-半乳糖主链组成的。β-(1-gt；6)-半乳糖侧链的长度从1个到20多个半乳糖残基不等，并且它们部分被单一的α-(1-gt；3)-L-阿拉伯呋喃糖基取代。此外，相当大比例的β-(1->6)-半乳聚糖侧链寡糖通过β-(1->6)-键在非还原末端被单一的4-O-甲基葡萄糖醛酸基残基取代。β-(1->；6)-半乳聚糖侧链偶尔会被α-L岩藻糖基取代。在缺乏岩藻糖的突变体中，AGPs缺乏这些岩藻糖修饰。这项工作证明了AGP结构中的拟南芥突变体是可以被鉴定和鉴定的。从拟南芥叶片中提取的AG多糖的详细结构解析对于深入了解这些分子的结构-功能关系是必不可少的，并将有助于对其生物合成的研究。
Proteins decorated with arabinogalactan (AG) have important roles in cell wall structure and plant development, yet the structure and biosynthesis of this polysaccharide are poorly understood. To facilitate the analysis of biosynthetic mutants, water-extractable arabinogalactan proteins (AGPs) were isolated from the leaves of Arabidopsis (Arabidopsis thaliana) plants and the structure of the AG carbohydrate component was studied. Enzymes able to hydrolyze specifically AG were utilized to release AG oligosaccharides. The released oligosaccharides were characterized by high-energy matrix-assisted laser desorption ionization-collision-induced dissociation mass spectrometry and polysaccharide analysis by carbohydrate gel electrophoresis. The Arabidopsis AG is composed of a beta-(1 -> 3)-galactan backbone with beta-(1 -> 6)-D-galactan side chains. The beta-(1 -> 6)-galactan side chains vary in length from one to over 20 galactosyl residues, and they are partly substituted with single alpha-(1 -> 3)-L-arabinofuranosyl residues. Additionally, a substantial proportion of the beta-(1 -> 6)-galactan side chain oligosaccharides are substituted at the nonreducing termini with single 4-O-methyl-glucuronosyl residues via beta-(1 -> 6)-linkages. The beta-(1 -> 6)-galactan side chains are occasionally substituted with alpha-L-fucosyl. In the fucose-deficient murus1 mutant, AGPs lack these fucose modifications. This work demonstrates that Arabidopsis mutants in AGP structure can be identified and characterized. The detailed structural elucidation of the AG polysaccharides from the leaves of Arabidopsis is essential for insights into the structure-function relationships of these molecules and will assist studies on their biosynthesis.