MECHANISTIC STUDIES OF A SIDE-ON COPPER NITROSYL COORDINATION BY NITRITE REDUCTA

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 亚硝酸盐还原酶（NiR）是一种含铜的酶，它进行细菌异化反硝化的第一个关键步骤，将亚硝酸盐还原为一氧化氮。来自粪产碱菌的亚硝酸盐还原酶作为确定高分辨率结构的模型系统，其提供了对生物学中这种重要酶的深入了解。在SSRL收集的数据导致了亚硝酰基铜的高分辨率结构，这显示了一个意想不到的和前所未有的侧面NO配位的金属。NiR与底物和产物复合的结构帮助我们修改了亚硝酸盐还原的催化机制，并为生物系统中一氧化氮金属相互作用的世界提供了见解。目前的结构的Cu（II）-NO-是通过减少晶体，并将它们暴露于NO。由于Cu（I）-NO+是建议的中间体的机制，需要一个高分辨率的结构与NO相互作用的氧化酶支持我们目前的解释催化。我们很幸运有一个生物系统，它可以作为铜NO化学的模型，也是反硝化的主要酶。该系统将用于确定反应中间体的高分辨率结构，研究NO结合的pH依赖性，并更好地了解NiR的催化潜力。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Nitrite reductase (NiR) is a copper-containing enzyme, which carries out the first committed step of bacterial dissimilatory denitrification, the reduction of nitrite to nitric oxide. Nitrite reductase from the bacterium Alcaligenes faecalis serves as a model system for determination of high-resolution structures, which provide insight into this vital enzyme in biology. Data collected at SSRL resulted in a high-resolution structure of a Cu-nitrosyl, which showed an unexpected and unprecedented side-on NO coordination to the metal. Structures of NiR complexed with substrate and product have helped us revise the catalytic mechanism of nitrite reduction and have provided insights into the world of nitric oxide metal interactions in a biological system. The current structure of Cu(II)-NO- was achieved by reducing the crystals first and exposing them to NO. Since Cu(I)-NO+ is the proposed intermediate in the mechanism, a high-resolution structure of an oxidized enzyme interacting with NO is needed for supporting our current interpretations of catalysis. We are fortunate to have a biological system, which can serve as a model for copper NO chemistry and is also a major enzyme in denitrification. This system will be used to determine a high-resolution structure of the reaction intermediate, study pH dependence of NO binding and better understand the catalytic potential of NiR.