CAREER: Harnessing Large Protein Conformational Changes to Perform Remarkable Chemical Reactions

有了这个奖项，化学部门的生命过程化学项目资助了密歇根大学安娜堡分校的Markos Koutmos博士，研究生物催化剂如何完成“不寻常的”或“不可能的”化学反应。维生素B12依赖的蛋氨酸合成酶（MS）是自然界最好的催化剂之一，在蛋氨酸的形成中起着不可或缺的作用，蛋氨酸是形成蛋白质的20种常见氨基酸之一。质谱催化或加速了在正常条件下（如温度、压力、浓度）不可能发生的反应。Koutmos实验室使用了三维结构测定和电子显微镜等技术，以及反应速率测量，以了解酶如何能够完成如此具有挑战性的反应。这项研究的最终目标是利用酶作为化学工具：重新编程质谱来催化合成应用所需的新反应。该项目与密歇根大学自然历史博物馆合作，整合到一个公众参与项目中，以提高高中和本科生的视觉交流和一般科学素养。与菲斯克大学（Fisk University）的化学家合作，让未被充分代表的少数族裔学生在密歇根大学（University of Michigan）参加暑期的研究项目。该研究项目旨在揭示酶动力学如何促进具有挑战性的化学反应的基本原理，并最终利用这些原理来重新编程生物酶以催化新的反应。瞬态动力学和结构生物学方法建立了MS模块安排如何支持三种不同的甲基转移酶反应。从机制研究中获得的信息为设计基于MS的工程蛋白和非天然/合成钴胺素类似物提供了信息，以创建可定制的生物催化系统，以指导MS在非规范底物上催化甲基化甚至烷基化的反应性。质谱是高度灵活的，包含广泛的域间接口，可以根据需要组装和拆卸，以支持化学反应。本研究确定了钴胺素辅助因子的随机运动、氧化态和配位环境如何影响酶可达到的构象态的动力学。来自这项研究的信息提供了对大型多模块酶如何重新排列以完成其反应的见解。这项研究有可能打开一个新的研究领域，研究如何重新设计甲基转移酶，以满足化学家有效和特异性转移甲基的需求。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

With this award, the Chemistry of Life Processes Program in the Chemistry Division is funding Dr. Markos Koutmos from the University of Michigan Ann Arbor to investigate how biological catalysts accomplish "unusual" or "improbable" chemical reactions. Vitamin B12 dependent methionine synthase (MS) is one nature's best catalysts, playing an integral role in the formation of methionine, one of the 20 commonly occurring amino acids that form proteins. MS catalyzes, or speeds up, a reaction that would be impossible under normal conditions (e.g., temperature, pressure, concentration). The Koutmos lab uses a combination of techniques, such as three-dimensional structure determinations and electron microscopy, along with reaction rate measurements, to understand how the enzyme is able to accomplish such a challenging reaction. The ultimate goal of this research is to use the enzyme as a chemical tool: reprogramming MS to catalyze novel, desired reactions for synthetic applications. This project is integrated into a public engagement program to enhance visual communication and general scientific literacy in high school and undergraduate students in cooperation with the University of Michigan Museum of Natural History. Collaboration with Fisk University chemists involves under-represented minority students in research projects at the University of Michigan during the summer.This research project seeks to uncover fundamental principles regarding how enzyme dynamics facilitate challenging chemical reactions and, ultimately, to exploit these principles in order to reprogram biological enzymes to catalyze new reactions. Transient kinetic and structural biology approaches establish how MS module arrangements support three distinct methyl transferase reactions. The information gained from the mechanistic studies informs the design of engineered MS-based proteins and unnatural/synthetic cobalamin analogs to create a customizable biocatalytic system to direct the reactivity of MS to catalyze methylations, or even alkylations, on noncanonical substrates. MS is highly flexible and contains extensive interdomain interfaces that are assembled and disassembled as needed to support the chemical reactions. This research establishes how stochastic motions, the oxidation state, and coordination environment of the cobalamin cofactor contribute to the dynamics of conformational states accessible to the enzyme. Information from this study provides insight into how large multi-modular enzymes rearrange to accomplish their reactions. The research has the potential to open a new area of research into how methyltransferases can be redesigned to address the need of chemists to efficiently and specifically transfer methyl-groups.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.