STRUCTURAL AND MECHANISTIC STUDIES OF XYLOGLUCAN XYLOSYLTRANSFERASE

这个子项目是利用资源的许多研究子项目之一。 由NIH/NCRR资助的中心拨款提供。对子项目的主要支持 子项目的首席调查员可能是由其他来源提供的， 包括美国国立卫生研究院的其他来源。为子项目列出的总成本可能 表示该子项目使用的中心基础设施的估计数量， 不是由NCRR赠款提供给次级项目或次级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中起着重要的作用，在人类的饮食中也具有重要的作用，同时也是工业中不可缺少的纤维和可再生生物燃料的来源。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。木葡聚糖木糖转移酶(XXT)是一种膜相关酶，在木葡聚糖的生物合成中起着关键作用。它催化木糖化反应，并将木糖加到β-1，4-葡聚糖骨架上。目前，关于细胞壁合成的分子机制，特别是多糖的生物合成，人们知之甚少。我们正在研究拟南芥的膜相关木糖聚糖木糖转移酶XXT2。AtXXT2蛋白得到了表达和纯化，并获得了结晶。我们将通过测定XXT的晶体结构来揭示其在原子水平上的独特结构特征，并剖析控制木糖化过程和细胞壁生物合成的反应机理。这项结构研究还将为操纵和设计细胞壁成分以提高在农业和工业(如生物燃料生产)以及食品营养和人类健康中具有重要影响的植物的质量提供结构指南。

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.