Collaborative Research: Bacterial manganese(IV) oxide biomineralization: Mechanism of Mn(II,III) oxidation by the multicopper oxidase complex

有了这个奖项，生命过程化学计划资助俄勒冈州健康与科学大学的布拉德利特博博士和华盛顿大学的托马斯斯皮罗博士进行一项关于锰在生命系统中如何氧化的合作研究调查。在这种氧化中形成的物质是各种形式的氧化锰。这些矿物质是环境中发现的最强氧化剂之一，在生物学和地质学意义上发挥着重要作用。它们通常被称为“海洋清道夫”，因为它们吸收有毒物质的能力很强。锰离子的生物氧化和通过酶形成锰氧化物的化学细节尚未阐明。Tebo博士和Spiro博士的研究检查了一种特定酶的作用，多铜锰氧化酶或MCO，它来自于生活在海洋中的细菌。在之前的研究中，研究人员能够分离出这种酶，并在此过程中发现，锰氧化似乎需要额外的蛋白质。当前的研究探讨了这些新发现的“辅助”蛋白的性质以及MCO和辅助蛋白催化的化学反应;结果可用于阐明细菌如何将海水中的锰转化为矿物质，发挥其在海水解毒中的重要作用。这项工作影响了我们对海洋学、地质学、生物学和生物化学等几个科学领域的理解。另一个广泛的影响是通过将包括高中在内的所有教育水平的学生纳入研究。研究人员通过一个科学的艺术项目向公众传播研究成果。来自不同大学的两个小组正在采用合作方法研究细菌锰Mn（II）氧化和由芽孢杆菌PL-12的多铜锰氧化酶（MCO）产生氧化锰的机制。通过细菌氧化溶解的Mn（II）形成氧化锰在水生和土壤环境中是重要的，并且是全球Mn循环中的关键途径，其通过许多酶的Mn催化中心支持生命。这一过程已经受到越来越多的技术关注，因为它导致高反应性的纳米颗粒矿物，可以分解有机分子并吸附其他金属离子，从而控制许多有毒和必需元素的分布和生物利用度。利用化学、生物化学和生物物理学的工具进行跨学科的努力，正在被用来阐明MCO氧化锰的机制。这种氧化以及MnO 2矿化发生的生化机制知之甚少。 多铜氧化酶已被牵连作为催化剂的Mn（II）氧化在许多模型系统的Mn（II）-氧化细菌，包括最近纯化的锰氧化酶复合物芽孢杆菌PL-12。 本项目旨在阐明芽孢杆菌锰氧化酶复合物进行两个连续的单电子氧化步骤并矿化锰的结构和机制。本研究的具体目标是：1）表征锰氧化酶复合物的铜中心; 2）确定锰氧化和氧进入的过程; 3）表征在MnO 2途径上形成的多核中间体; 4）描述活性复合物表达所需的辅助蛋白的作用;和5）阐明酶复合物和出现的氧化物的结构。X射线晶体学和光谱学方法正在与基本的生物化学技术结合使用，以实现这些目标。

With this award, the Chemistry of Life Processes Program is funding Dr. Bradley Tebo of Oregon Health and Science University and Dr. Thomas Spiro of the University of Washington for a collaborative research investigation of how manganese is oxidized in living systems. The substances formed in this oxidation are various forms of manganese oxide. These minerals are some of the strongest oxidants found in the environment and play important roles in both a biological and a geological sense. They are often called "scavengers of the sea" because of their great ability to absorb toxic substances. The chemical details of the biological oxidation of manganese ions and formation of manganese oxides by enzymes are not yet elucidated. The research of Dr. Tebo and Dr. Spiro examines the role of a specific enzyme, multicopper manganese oxidase, or MCO, that is derived from a bacterium that lives in the ocean. In previous research, the investigators were able to isolate the enzyme and, in the process, found that additional proteins seem necessary for the manganese oxidation. The current research addresses the nature of these newly discovered "helper" proteins and the chemistry catalyzed by MCO and the helper proteins; the results can be used to shed light on how the bacterium converts manganese in seawater to the mineral exerts its important role in detoxifying seawater. The work impacts our understanding of several areas of science including oceanography, geology, biology and biochemistry. Another broad impact is through the inclusion of students at all educational levels, including high school, in the research. The investigators disseminate insights obtained from research to the general public through a science-in-art project.A collaborative approach involving the two groups from different universities is being used to study the mechanism of bacterial manganese Mn(II) oxidation and manganese oxide production by the multicopper Mn oxidase (MCO) from Bacillus sp. PL-12. The formation of manganese oxide by bacterial oxidation of dissolved Mn(II) is important in aquatic and soil environments and is a key pathway in the global Mn cycle, which supports life through the Mn catalytic centers of many enzymes. This process has received increased technological interest because it leads to highly-reactive, nanoparticulate minerals, which can break down organic molecules and adsorb other metal ions, thereby controlling the distribution and bioavailability of many toxic and essential elements. An interdisciplinary effort using tools from chemistry, biochemistry and biophysics is being used to elucidate the mechanism of manganese oxidation by MCO. The biochemical mechanism by which this oxidation, as well as MnO2 mineralization, occurs is poorly understood. Multicopper oxidase enzymes have been implicated as catalysts for the Mn(II) oxidation in many model systems for Mn(II)-oxidizing bacteria, including the recently purified Mn oxidase complex from Bacillus sp. PL-12. In this project, the structure and mechanism by which the Mn oxidase complex from Bacillus sp. carries out two sequential one-electron oxidation steps and mineralize Mn is being elucidated. The specific objectives of the research are: 1) to characterize the copper centers of the Mn oxidase complex; 2) to determine the course of Mn oxidation and oxygen entry; 3) to characterize polynuclear intermediates formed on the pathway to MnO2; 4) to describe the role of ancillary proteins required for the expression of the active complex; and 5) to elucidate the structure of the enzyme complex and emerging oxides. X-ray crystallography and spectroscopic methods are being used in conjunction with basic biochemistry techniques to achieve these objectives.