STRUCTURAL AND MECHANISTIC STUDIES OF XYLOGLUCAN XYLOSYLTRANSFERASE

这个子项目是许多利用资源的研究子项目之一 由NIH/NCRR资助的中心拨款提供。子项目的主要支持 而子项目的主要调查员可能是由其他来源提供的， 包括其它NIH来源。 列出的子项目总成本可能 代表子项目使用的中心基础设施的估计数量， 而不是由NCRR赠款提供给子项目或子项目工作人员的直接资金。 植物细胞壁多糖是植物中含量最丰富的有机分子，在植物性食品的品质和人类饮食中具有重要作用，同时也是工业中重要的纤维和可再生生物燃料来源。木葡聚糖是大多数植物初生细胞壁中的主要半纤维素多糖。木葡聚糖木糖基转移酶（XXT）是一种膜结合酶，是木葡聚糖生物合成的关键酶。它催化木糖基化反应并将木糖添加到β-1，4-葡聚糖主链上。目前，对细胞壁合成，特别是多糖生物合成的分子机制知之甚少。我们正在研究拟南芥中的膜相关木葡聚糖木糖基转移酶XXT 2。AtXXT 2蛋白在大肠杆菌中得到了表达和纯化，并获得了晶体。我们将确定XXT晶体结构，以揭示在原子水平上的独特结构特征，并剖析木糖基化过程和细胞壁生物合成的反应机制。这种结构研究还将为细胞壁组成的操纵和工程化提供结构指导，以改善在农业和工业中具有重要影响的植物的质量（例如，生物燃料生产）以及食物营养和人类健康。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Plant cell wall polysaccharides are the most abundant organic molecules and play important roles in the quality of plant-based foods and have beneficial effects in human diets, and they are also the essential materials in industry as a source of fibers and renewable biofuel. Xyloglucan is the principal hemicellulosic polysaccharide in the primary cell walls of most plants. Xyloglucan xylosyltransferase (XXT) is membrane-associated enzyme and a key player in the biosynthesis of xyloglucans. It catalyzes xylosylation reaction and adds xylose onto beta-1,4-glucan backbone. Currently, little is known about the molecular mechanisms underlying the cell wall synthesis, particularly the polysaccharide biosynthesis. We are studying membrane-associated xyloglucan xylosyltransferase XXT2 from Arabidopsis. AtXXT2 protein was expressed and purified, and crystals were obtained recently. We will determine XXT crystal structures to reveal the unique structural features at the atomic level and dissect the reaction mechanism governing the xylosylation process and the cell wall biosynthesis. This structural study will also provide a structural guide for manipulation and engineering of cell wall composition to improve the quality of plants with important impacts in agriculture and industry (e.g., biofuel production) as well as food nutrition and human health.