CRYSTALLOGRAPHIC STUDIES OF PROTEIN STRUCTURE & FUNCTION

这项研究计划的总体目标是了解 镁离子在催化反应机理中的作用 碳水化合物加工金属酶。 研究人员还希望 了解蛋白质动力学如何与金属蛋白质功能结合， 稳定 为了实现这些目标，我们使用我们拥有的新方法， 在过去的几年里，包括冷冻脑血管造影术， 和时间分辨晶体学 有三个相互依存的 在这个大项目中的子项目。 第一个继续研究 木糖异构酶。 调查人员正在确定 以推断镁离子在 催化开环反应。 然后，我们将模拟 量子力学/分子生物学相结合的全催化途径 力学，以了解桥连的独特催化性能 心脏病。 第二个项目的重点是 镁在3-异丙基苹果酸催化反应中的作用 脱氢酶。 研究人员将使用X射线和 晶体学和遗传选择来绘制 热稳定性、蛋白质柔性和金属依赖性活性 在这种必需的氨基酸合成酶中。 最后我们将 确定了双官能团的结构和催化机理 铜绿假单胞菌甘露糖-6-磷酸异构酶。 这 酶催化藻酸盐生产中的两个非连续反应： 这两种反应都需要镁离子。 这三种酶都能 低温或劳厄晶体学， E-S络合物和反应中间体可以在 或者是单一底物/单一产物酶，其中 生产性Nfichaelis复合物可以直接在 在平衡条件下结晶。

The overall objective of this research program is to understand the role of magnesium ion in the catalytic mechanisms of carbohydrate-processing metalloenzymes. Investigators also wish to learn how protein dynamics if coupled to metalloprotein function and stability. To achieve these aims, we use novel methods that we have developed over the last several years, including cryocrystallography and time-resolved crystallography. There are three interdependent sub-projects within this overall project. The first continues studies of xylose isomerase. The investigators are determining the structure of the initial E-S complex to deduce therole of the magnesium ions in catalysis of the ring-opening reaction. We will then simulate the entire catalytic pathway by combined quantum mechanics/molecular mechanics, to understand the unique catalytic properties of bridged bimetallic centers. The second project focuses on the role of magnesium in the reaction catalyzed by 3-isopropylmalate dehydrogenase. Investigators will usea combination of X-ray crystallography and genetic selection to map the correlations between thermal stability, protein flexibility, and metal-dependent activity in this essential arnino-acid synthesizing enzyme. Finally, we will determine the structure and catalytic mechanism of the bifunctional mannose-6-phosphate isomerase from Pseudomonay aeruginosa. This enzyme catalyzes two non-contiguous reactions in alginate production: Both reactions require magnesium ion. All three enzymes are amenable to low temperature or Laue crystallography, so that transient E-Scomplexes and reaction intermediates can be trapped and studied at high resolution; or are single substrate/single product enzymes, where the productive Nfichaelis complex can be observed directly in the crystal under equilibrium conditions.