BIOINORGANIC CHEMISTRY--CARBON MONOXIDE DEHYDROGENASE

描述：该提案旨在阐明催化机制 一氧化碳脱氢酶。 的 酶的镍和铁硫簇的结构，它们的氧化还原 和光谱特性，它们在催化中的作用，以及它们的 与蛋白质结构的关系是特别感兴趣的。 只有四种含镍的酶是已知的， Ni的性质还不太清楚。 镍配合物被广泛应用于 作为工业催化剂，它们用于特异性地切割DNA位点。 更详细地了解镍的催化性能可能有助于 开发具有生物医学和 生物技术应用。 这种酶催化两种类型的反应， CO到CO2和乙酰辅酶A的合成。 这种酶具有 a2b2四元结构，具有2Ni、11 - 13 Fe和约14 S2- 离子/ab。 金属离子被组织成三种类型的簇， 分别是A B和C C-和A-团簇是新型的Ni-Fe-S团簇， 作为活性位点，而B簇是Fe4S4簇， 用于将电子转移到外部电子接受剂。 的 采取的主要方法涉及并涉及将 以不破坏金属的方式破坏酶的亚基 集群 通过研究单个亚基和其他解离 产品，个别集群的所需性能将是 阐明。 将使用各种物理方法，包括 电子顺磁共振，穆斯堡尔，电子核双 共振，X射线吸收，电子吸收，圆二色性， 荧光，质谱，可能还有核磁共振 共振 其他方法，包括动力学、电位滴定法 滴定、活性测定、放射性和同位素标记， 分析超离心、平衡透析和肽 还将采用测序。

DESCRIPTION: This proposal aims to elucidate the catalytic mechanism of carbon monoxide dehydrogenase from Clostridium thermoaceticum. The structure of the enzyme's nickel and iron-sulfur clusters, their redox and spectroscopic properties, their roles in catalysis, and their relationship to the structure of the protein are of particular interest. Only four nickel containing enzymes are known, and the biochemical properties of Ni are not well understood. Ni complexes are widely used as industrial catalysts, and they serve to cleave DNA site specifically. More detailed knowledge of the catalytic properties of Ni may facilitate development of improved artificial enzymes with biomedical and biotechnological applications. The enzyme catalyses two types of reactions, the reversible oxidation of CO to CO2 and the synthesis of acetyl-coenzyme A. The enzyme has an a2b2 quaternary structure with 2Ni, 11-13 Fe, and approximately 14 S2- ions per ab. The metal ions are organized into three types of clusters, called A,B, and C. The C-and A-clusters are novel Ni-Fe-S clusters that serve as the active sites, while the B-cluster is an Fe4S4 cluster that serves to transfer electrons to external electron-accepting agents. The predominant approach to be taken involves and has involved separating the subunits of the enzyme in a manner that does not destroy the metal clusters. By studying individual subunits and other dissociation products, the desired properties of individual clusters will be elucidated. A variety of physical methods will be used, including Electron Paramagnetic Resonance, Mossbauer, Electron Nuclear Double Resonance, X-ray Absorption, Electronic Absorption, Circular Dichroism, Fluorescence, Mass Spectrometry, and possibly Nuclear magnetic Resonance. Other methods, including kinetics, potentiometric titrations, activity assays, radioactivity and isotope labeling, analytical ultracentrifugation, equilibrium dialysis, and peptide sequencing will also be employed.