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，该反应的功能是指导电子在大分子之间的运动，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，因为在远程电荷迁移过程中，反应蛋白残基充当电子或电子空位(空穴)的中转站。了解这种所谓的电子或空穴“跳跃”对于调整蛋白质的关键性质以进行能量转换非常重要。这个项目将应用光谱和结构技术来研究多步ET在模型系统和本地生物光传感器中的作用，以测试机制和设计新的功能。这些研究还将在光遗传学、开发和使用工程光敏蛋白来控制细胞过程(包括昼夜节律)方面具有重要的前景。该项目将涉及研究生和本科生在酶学、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等领域的尖端研究。该项目的协作性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。该项目还将与国际学生联合会正在开发的一个项目相结合，该项目旨在吸引代表人数不足的群体的学生参与科学研究。该项目旨在了解涉及光活性蛋白质中反应性蛋白质侧链(即跳跃)的多步ET反应。通过对由细胞色素c、细胞色素c、过氧化物酶和细胞色素c组成的光敏模型体系的动力学和结构的研究，探讨色氨酸/酪氨酸跳跃中心通过系统地扰动自由基环境和在跳跃部位加入非天然氨基酸的反应活性。蓝光传感中的空穴跳跃、隐色素和光氧电压(LOV)光感受器的耦合工作将探索生物物理属性，这些属性允许反应蛋白侧链在这些含有黄素的光传感器中介导快速而稳定的电荷分离。对于一类新的LOV样蛋白，涉及非芳香族残基的多步ET将被研究。这些系统的重新设计将检验假设，确认机制，并为光遗传学的应用开发工具，光遗传学是利用光调节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.