BIOLOGICAL METAL CLUSTERS--BIOPHYSICAL AND MODEL STUDIES

描述：需要两种或两种以上金属的酶和蛋白质活性部位 活性中心现在是生物化学的显著特征。示例 已知的涉及铁原子的生物金属团簇(例如 铁氧还蛋白、亚硫酸盐还原酶、三氯氰菊酯、核苷酸还原酶、 甲烷单加氧酶)、铜原子(例如血蓝蛋白、酪氨酸酶、 铜蓝蛋白，细胞色素氧化酶中的CuA)，锰原子(例如光系统II， 过氧化氢酶)、镍原子(尿素酶)和一种以上的金属，或 杂多核团簇(例如，超氧化物歧化酶、铜、锌；固氮酶， 钼，铁；细胞色素氧化酶，血红素A3，CuB；氢酶，乙酰辅酶A 合酶、一氧化碳脱氢酶、镍、铁)。的不同功能 团簇包括电子传输，质子梯度的建立， 氧结合，氧活化，DNA合成方面，水解性 反应和氧化还原反应，包括氮气和氧气还原 以及二氢、一氧化碳和水氧化。尽管有大量的 生物金属团簇已经被表征，仅在少数几个 实例具有与多核活动关联的唯一属性 地点已被划定。对于杂多核来说尤其如此。 集群。拟议研究的最终目标是了解 与金属簇合物催化有关的优点及其各自的特点 为其特定目的而设计的。这一知识将提供详细的 了解涉及金属簇的酶机制，将有助于 酶抑制剂(如药物)和工业催化剂的设计 所涉及的化学反应。这项建议侧重于理解 含镍氢酶的结构和功能是关键 微生物中厌氧代谢中的酶，最近被证明 含有一个新的异双核Ni，Fe活性中心。因此，拟议的 研究还影响了我们对镍的生物学作用的理解， 其中包括幽门螺杆菌的生殖力，一种已经被 与胃溃疡和胃癌有关。具体目标： 氢酶的结构和功能包括：(1)建立 催化剂中活性中心Ni和Fe中心的关系 机理，(2)确定镍和铁位的功能，包括 金属配体；(3)阐明了酶催化的优点 与异双核部位和Se的掺入有关。这些 目标将通过应用于以下方面的物理技术组合来实现 氢酶和模拟系统，这些系统被设计来模拟特定的 酶活性部位的结构或功能方面。

DESCRIPTION: Enzyme and protein active sites that require two or more metal centers for activity are now prominent features of biochemistry. Examples of biological metal clusters are known that involve Fe atoms (e.g. ferredoxins, sulfite reductase, hemerythrin, ribonucleotide reductase, methane monooxygenase), Cu atoms (e.g. hemocyanin, tyrosinase, ceruloplasmin, CuA in cytochrome oxidase), Mn atoms (e.g. photosystem II, catalase), Ni atoms (urease), and more than one kind of metal, or heteropolynuclear clusters (e.g. superoxide dismutase, Cu, Zn; nitrogenase, Mo, Fe; cytochrome oxidase, heme a3, CuB; hydrogenase, acetyl coenzyme A synthase, carbon monoxide dehydrogenase, Ni, Fe). The diverse functions of the clusters include electron transport, establishment of proton gradients, dioxygen binding, dioxygen activation, aspects of DNA synthesis, hydrolytic reactions, and redox reactions including dinitrogen and dioxygen reduction and dihydrogen, CO and water oxidation. Despite the large number of biological metal clusters that have been characterized, only in a few instances have the unique properties associated with polynuclear active sites been delineated. This is particularly true for heteropolynuclear clusters. The ultimate goals of the proposed research are to understand the advantages associated with catalysis by metal clusters and how each is designed for its specific purpose. This knowledge will provide a detailed understanding of enzyme mechanisms involving metal clusters and will aid in the design of inhibitors of enzymes (e.g. drugs) and industrial catalysts for the chemical reactions involved. This proposal focuses on understanding the structure and function of Ni-containing hydrogenases, which are key enzymes in anaerobic metabolism in microbes and have recently been shown to contain a novel heterodinuclear Ni, Fe active site. Thus, the proposed research also impacts on our understanding of the biological roles of Ni, which include the virility of Helicobacter pylori, a bacterium that has been associated with gastric ulcers and stomach cancer. Specific goals regarding the structure and function of hydrogenase include: (1) establishing the relationship between the active site Ni and Fe centers in the catalytic mechanism, (2) determining the functions of the Ni and Fe site, including the metal ligands, and (3) elucidating the advantages to enzyme catalysis associated with a heterodinuclear site and with incorporation of Se. These goals will be met by using a combination of physical techniques applied to hydrogenases and to model systems that are designed to model specific aspects of the structure or function of the enzyme active site.