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

通过这一奖项，生命过程化学计划资助俄勒冈健康与科学大学的Bradley Tebo博士和华盛顿大学的Thomas Spiro博士共同研究生命系统中锰是如何被氧化的。在这种氧化过程中形成的物质是各种形式的氧化锰。这些矿物是环境中发现的一些最强的氧化剂，在生物和地质意义上都发挥着重要作用。它们常被称为“海洋食腐动物”，因为它们有很强的吸收有毒物质的能力。锰离子的生物氧化和酶形成锰氧化物的化学细节尚不清楚。特博博士和斯皮罗博士的研究考察了一种特定的酶的作用，这种酶是从生活在海洋中的细菌中提取的一种特殊的酶，即多铜锰氧化酶。在之前的研究中，研究人员能够分离出这种酶，并在这个过程中发现，更多的蛋白质似乎是锰氧化所必需的。目前的研究涉及这些新发现的“辅助”蛋白质的性质以及由MCO和辅助蛋白质催化的化学；这些结果可用于阐明细菌如何将海水中的锰转化为矿物，并在海水中发挥其重要的解毒作用。这项工作影响了我们对几个科学领域的理解，包括海洋学、地质学、生物学和生物化学。另一个广泛的影响是将所有教育水平的学生包括在研究中，包括高中。研究人员通过一个科学技术项目向公众传播从研究中获得的见解。来自不同大学的两个小组正采用合作的方法，研究细菌锰(II)氧化和芽孢杆菌多铜锰氧化酶(MCO)产生锰氧化物的机制。PL-12。细菌氧化溶解的锰(II)形成氧化锰在水生和土壤环境中具有重要意义，是全球锰循环的关键途径，通过许多酶的锰催化中心维持生命。这一过程引起了越来越多的技术兴趣，因为它产生了高活性的纳米颗粒矿物，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可利用性。利用化学、生物化学和生物物理学的工具，一项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MnO2矿化发生的生化机制还知之甚少。多铜氧化酶在许多氧化锰细菌的模型体系中被认为是锰(II)氧化的催化剂，包括最近从芽孢杆菌中提纯的锰氧化酶络合物。PL-12。本课题对芽孢杆菌锰氧化酶复合体的结构和作用机理进行了研究。进行了两个连续的单电子氧化步骤，并对锰进行了矿化。这项研究的具体目标是：1)表征锰氧化酶复合体的铜中心；2)确定锰氧化和氧进入的过程；3)表征在通往MnO2的途径上形成的多核中间体；4)描述活性复合体表达所需的辅助蛋白的作用；以及5)阐明酶复合体和新出现的氧化物的结构。X射线结晶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.