Understanding multistep electron transfer reactions for the design of photsensory proteins

在生物系统中，许多代谢过程涉及电子转移（ET）反应，其功能是引导大分子之间的电子运动，而不会耗散驱动化学转化所需的高自由能。ET通常是多步骤的，因为反应性蛋白质残基在长距离电荷迁移过程中充当容纳电子或其空位（“空穴”）的停留点。理解这种所谓的电子或空穴“跳跃”对于适应蛋白质的关键特性以实现能量转换非常重要。该项目将应用光谱和结构技术来研究多步ET在模型系统和原生生物光传感器中的作用，以测试机制和设计新功能。这些研究也将对光遗传学，开发和使用工程光敏蛋白控制细胞过程，包括昼夜节律，具有重要的前景。 该项目将涉及研究生和本科生在前沿研究领域，包括酶学，蛋白质生物化学，结构生物学，光谱学，化学动力学和蛋白质工程。 该项目的协作和多学科性质将使学生接触到连接学科和科学文化的研究。该项目还将与PI开发的一个正在进行的项目相结合，以吸引来自代表性不足群体的学生参与科学研究。 该项目旨在了解涉及反应蛋白侧链的多步ET反应（即，跳跃）。 动力学和结构研究的光敏模型系统组成的氧化还原合作伙伴细胞色素c过氧化物酶和细胞色素c将探讨色氨酸/酪氨酸跳跃中心的反应性的自由基环境的系统扰动和纳入非天然氨基酸的跳跃网站。 在蓝光感应隐花色素和光-氧-电压（LOV）光感受器中的空穴跳跃的耦合工作将探测允许反应蛋白侧链介导这些含黄素的光传感器中的快速和稳定的电荷分离的生物物理属性。对于一类新的LOV样蛋白，涉及非芳香残基的多步ET将被研究。这些系统的重新设计将测试假设，确认机制并开发光遗传学应用的工具，光遗传学是由光调控的工程细胞系统领域。

In biological systems, many metabolic processes involve electron transfer (ET) reactions, which function to direct the movement of electrons among macromolecules without dissipating the high free energy needed to drive chemical transformations. ET is often multi-step in that reactive protein residues act as waystations to harbor electrons or their vacancies ('holes') during long-range charge migration. Understanding this so-called electron, or hole, 'hopping' is important for adapting key properties of proteins for the purpose of energy conversion. This project will apply spectroscopic and structural techniques to study the role of multi-step ET in model systems and in native biological light sensors to test mechanisms and design new functionality. These studies also will have important prospects for optogenetics, the development and use of engineered photosensitive proteins for controlling cellular processes, including circadian rhythms, with light. The project will involve graduate and undergraduate students in cutting edge research in fields including enzymology, protein biochemistry, structural biology, spectroscopy, chemical kinetics, and protein engineering. The collaborative and multidisciplinary nature of the project will expose students to research that bridges disciplines and scientific cultures. The project will also couple to an on-going program developed by the PI to engage students from under-represented groups in scientific research. This project aims to understand multi-step ET reactions that involve reactive protein side chains (i.e., hopping) in photoactive proteins. Kinetic and structural studies of a photosensitive model system composed of redox partners cytochrome c peroxidase and cytochrome c will explore the reactivity of a Tryptophan/Tyrosine hopping center by systematic perturbation of the radical environment and incorporation of non-natural amino acids at the hopping site. Coupled work on hole-hopping in blue-light sensing cryptochromes and Light- Oxygen- Voltage (LOV) photoreceptors will probe the biophysical attributes that allow reactive protein side chains to mediate rapid and stable charge separation in these flavin-containing photosensors. For a new class of LOV-like protein, multi-step ET involving non-aromatic residues will be investigated. Redesign of these systems will test hypotheses, confirm mechanisms and develop tools for applications of optogenetics, the field of engineering cellular systems to be regulated by light.