CRYSTALLOGRAPHIC STUDIES OF PROTEIN STRUCTURE & FUNCTION

这项研究计划的总体目标是了解 镁离子在黄曲霉毒素催化机理中的作用 碳水化合物加工金属酶。调查人员还希望 了解蛋白质动力学如何与金属蛋白的功能和 稳定性。为了实现这些目标，我们使用我们拥有的新方法 在过去的几年里发展起来的，包括晶体学 和时间分辨结晶学。有三个相互依存的关系 此整体项目中的子项目。第一个人继续学习 木糖异构酶。调查人员正在确定结构 用初始E-S络合物推算镁离子的价态 开环反应的催化作用。然后，我们将模拟 量子力学/分子相结合的全催化途径 力学，以了解桥联分子的独特催化性能 双金属中心。第二个项目的重点是 苹果酸3-异丙酯催化反应中的镁 脱氢酶。调查人员将使用一种组合X光 结晶学和遗传选择之间的相关性 热稳定性、蛋白质柔韧性和金属依赖活性 在这种必需的氨基酸合成酶中。最后，我们会 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 在藻酸盐生产中，酶催化两个不连续的反应： 这两个反应都需要镁离子。这三种酶都是柔顺的。 以低温或劳氏结晶学，使瞬变 E-S络合物和反应中间体可以在以下位置捕获和研究 高分辨率；或者是单一底物/单一产物酶，其中 多产的奈菲查里斯复合体可以直接在 平衡条件下的结晶。

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.