Recognition and Deconstruction of Uronic Acid-Containing Polysaccharides

除了公认的碳水化合物作为营养来源的作用之外，多糖、蛋白聚糖和糖脂形式的复合碳水化合物可被认为是“细胞的语言”，因为它们介导许多完整的生物事件。在努力破译的作用，一类碳水化合物，含糖醛酸多糖（UCPs），在这些过程中发挥，我将追求的结构和功能特性的蛋白质参与碳水化合物的识别和代谢。UCP在组成上相似，因为它们由重复元素组成，这些重复元素包括β-D-葡糖醛酸、α-D-半乳糖醛酸、α-D-4-O-甲基葡糖醛酸或它们沿链长的沿着衍生物。然而，尽管这种成分相似，UCPs介导许多不同的生物相互作用和细胞信号传导事件。举例来说：UCP在细胞和组织表面贡献独特的机械、粘弹性和渗透势，它们参与整个细胞外基质的配体、营养和细胞运动，并且它们与各种效应分子相互作用以介导细胞内相互作用。虽然我的研究的长期目标将解决一般的UCP，最初的重点将是两种碳水化合物，特别是透明质酸和果胶（同型半乳糖醛酸）。本研究的重点是基于这样的假设：微生物系统的结构和功能重建UCP代谢将弥合之间的知识差距的微妙差异UCP组成和其不同的生物功能。 尽管透明质酸和果胶作为无毒复合物具有生物学意义和工业相关性，但它们的代谢在很大程度上是糖生物学的一个研究不足的分支。例如，在过去的三年里，已经报道了一类新的果胶降解酶，我自己的工作已经确定了第一个微生物透明质酸结合蛋白。因此，我应用了一种基于发现的生物信息学方法来识别一系列新的透明质酸和果胶相关基因，这将是我们拟议的研究计划的重点。该计划的长期目标是通过3-D结构测定研究透明质酸和果胶识别和代谢蛋白质因子，并使用支持性动力学和热力学技术来探测分子相互作用和作用机制。具体来说，我和我的学员将使用X射线晶体学和小角X射线散射进行结构表征和各种互补的分子表征技术，包括生物信息学，糖生物学，酶学，量热法和蛋白质生物化学，以关联结构和功能。这种统一的分子表征和功能分析方法将使我们能够从多个角度解决重要的生物过程，并增强我们研究计划的总体目标的影响，这是为了丰富我们对透明质酸和果胶代谢的理解;两种突出的多糖分别对细胞外基质和植物细胞壁中生物事件的协调做出了相当大的贡献。

Beyond the universally recognized role for carbohydrates as nutrient sources, complex carbohydrates in the form of polysaccharides, proteoglycans, and glycolipids may be considered to be the “the language of the cell” in that they mediate many integral biological events. In an effort to decipher the role that a class of carbohydrates, the uronic-acid containing polysaccharides (UCPs), play in these processes, I will pursue the structural and functional characterization of the proteins involved in carbohydrate recognition and metabolism. UCPs are compositionally similar in that they are made up of repeating elements that include either beta-D-glucuronic acid, alpha-D-galacturonic acid, alpha-D-4-O-methylglucuronic acid, or their derivatives along the chain lengths. However, despite this compositional similarity, UCPs mediate many diverse biological interactions and cell-signaling events. For example: UCPs contribute unique mechanical, viscoelastic, and osmotic potential at cell and tissue surfaces they participate in ligand, nutrient, and cellular motility throughout the extracellular matrix, and they interact with a variety of effector molecules to mediate intracellular interactions. While the long-term objective of my research will address UCPs in general, the initial focus will be on two carbohydrates in particular, hyaluronan and pectin (homogalacturonate). This research focus is based on the hypothesis: that structural and functional reconstruction of microbial systems for UCP metabolism will bridge the knowledge gap between subtle differences in UCP composition and their diverse biological functions. Despite their biological significance and industrial relevance as non-toxic composites, hyaluronan and pectin metabolism is a largely underexplored branch of glycobiology. For example, a novel class of pectin-degrading enzymes has been reported within the past three years and my own work has identified the first microbial hyaluronan binding protein. I have therefore applied a discovery-based bioinformatics approach to identify a series of novel hyaluronan and pectin-related genes that will be the focus of our proposed research program. The long-term objective of the program is to study hyaluronan and pectin recognition and metabolizing protein factors by 3-D structure determination, and to use supportive kinetic and thermodynamic techniques to probe molecular interactions and mechanisms of action. Specifically, my trainees and I will use X-ray crystallography and Small Angle X-ray Scattering for structural characterization and various complementary molecular characterization techniques, including bioinformatics, glycobiology, enzymology, calorimetry and protein biochemistry, to correlate structure and function. This unified approach to molecular characterization and functional analyses will allow us to address important biological processes from multiple perspectives and enhances the impact of the overarching objective of our research program, which is to enrich our understanding of hyaluronan and pectin metabolism; two prominent polysaccharides that make considerable contributions to the coordination of biological events in the extracellular matrix and plant cell walls, respectively.