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利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 亚硝酸盐还原酶(NIR)是一种含铜的酶，它执行细菌异化反硝化的第一步，即将亚硝酸盐还原为一氧化氮。来自粪产碱细菌的亚硝酸盐还原酶作为一个模型系统来确定高分辨率结构，这为我们提供了对生物学中这种重要酶的洞察。在SSRL收集的数据导致了一个高分辨率的铜-亚硝基结构，它显示了一个意想不到的和前所未有的侧面-没有与金属配位。NIR与底物和产物的络合结构帮助我们修正了亚硝酸盐还原的催化机理，并为深入了解生物体系中一氧化氮与金属的相互作用提供了新的视角。铜(II)-NO-的当前结构是通过首先还原晶体并将其暴露在NO中而实现的。由于铜(I)-NO+是该反应的中间体，因此需要一个与NO相互作用的氧化酶的高分辨结构来支持我们目前对催化作用的解释。幸运的是，我们有一个生物系统，它可以作为铜的非化学模型，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结构，研究NO结合的pH依赖性，并更好地了解近红外的催化潜力。

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.