Protein Control of Electron Transfer Pathways in Photosynthesis

光合作用中电子传递途径的蛋白质控制

• 批准号: 0642260
• 负责人: Neal Woodbury
• 金额: $ 117.13万
• 依托单位: Arizona State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-04-01 至 2013-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0642260&HistoricalAwards=false
• 关键词: Protein; Control; Electron; Transfer; Pathways

The initial solar energy conserving event in photosynthesis is the transfer of an electron between an excited donor and a neighboring acceptor molecule in the reaction center, an intrinsic membrane protein-pigment complex. In this project the PI will continue his studies of the purple nonsulfur bacterium Rhodobacter sphaeroides, investigating the driving force and temperature dependence of the initial electron transfer reactions. The PI has used a form of reaction diffusion theory, applied previously to electron transfer in viscous solvents, to describe the complex kinetics of electron transfer as a function of driving force and temperature. This approach has been remarkably successful, implying that protein conformational changes initiated by light absorption control the observed kinetics instead of a static barrier crossing between two potential surfaces. Several important questions have been raised by this work that need to be answered. First, the nature of the protein motion and the spectroscopic signal at 280 nm that appears to be a probe of this motion are unclear. It is currently hypothesized that this is due to tryptophan residues responding to changes in the protein environment, but this remains to be proven. Second, a more detailed mechanistic exploration of the relationship between protein relaxation and electron transfer is necessary. This new model provides an opportunity to determine the reorganization energy, driving force and coupling for a whole series of mutants as a function of temperature, resulting in a much more complete mechanistic picture of initial photosynthetic electron transfer than has ever been available previously. Finally, this work will be merged with current directed evolution approaches to produce mutants that undergo high yield electron transfer along the normally unused cofactor pathway (the B-side). A very similar set of studies as a function of driving force and temperature will then be performed on these mutants to explore the mechanistic similarities and differences between the two electron transfer pathways. The PI is involved in expanding interdisciplinary research at both the graduate and undergraduate levels. The PI has seven undergraduates working with him, two directly on this project. In addition, the concepts involved in photosynthetic research are used to enrich his teaching in both physical chemistry and biochemistry. For example, the PI teaches a course on bio-nanotechnology as part of a learning community project at ASU in which sophomores explore the science, policy and sociology of nanotechnology. The PI is also the director of an NSF IGERT program in biomolecular nanotechnology. The photosynthetic reaction center is a premier example of an optoelectronic device at the nanoscale and the concepts from this work are one of the key examples of biomolecular nanotechnology studied by the IGERT students. The PI is also the current director of the ASU BioEnergy Research Initiative, a new initiative growing out of ASU's Photosynthesis Center that seeks to take our growing understanding of photosynthetic processes and utilize them in the development of new energy sources and means of energy transduction. Finally, the PI directs the Center for BioOptical Nanotechnology in the Biodesign Institute. In this role, he directly interfaces with a large number of private, commercial and citizens groups, and these discussions form the basis for a new approach to community-embedded research, in which the needs of society and the process of discovery are integrated in a new hybrid model for interdisciplinary research. This project is jointly supported by Molecular Biophysics in the Division of Molecular and Cellular Biosciences in the Directorate for Biological Sciences and the Experimental Physical Chemistry Program in the Division of Chemistry in the Mathematical and Physical Sciences Directorate.

在光合作用中，最初的太阳能保存事件是电子在反应中心（内在膜蛋白-色素复合物）中的激发供体和相邻受体分子之间的转移。在这个项目中，PI将继续研究紫色非硫细菌Rhodobacter sphaeroides，研究初始电子转移反应的驱动力和温度依赖性。 PI已经使用了一种形式的反应扩散理论，以前应用于粘性溶剂中的电子转移，来描述作为驱动力和温度的函数的电子转移的复杂动力学。这种方法已经取得了显着的成功，这意味着蛋白质的构象变化引发的光吸收控制所观察到的动力学，而不是一个静态的两个潜在的表面之间的障碍交叉。 这项工作提出了几个需要回答的重要问题。 首先，蛋白质运动的性质和280 nm处的光谱信号（似乎是这种运动的探针）尚不清楚。 目前假设这是由于色氨酸残基响应蛋白质环境的变化而引起的，但这仍有待证明。第二，更详细的机制探索蛋白质松弛和电子转移之间的关系是必要的。 这个新的模型提供了一个机会，以确定重组能量，驱动力和耦合作为温度的函数的整个系列的突变体，导致在一个更完整的机械图片的初始光合电子转移比以往任何时候都可用。 最后，这项工作将与目前的定向进化方法相结合，以产生沿着通常未使用的辅因子途径（B侧）进行高产电子转移的突变体。 一组非常相似的研究作为驱动力和温度的函数，然后将在这些突变体上进行，以探索两种电子转移途径之间的机制相似性和差异。PI参与扩大研究生和本科生层面的跨学科研究。 PI有七名本科生与他一起工作，其中两名直接参与这个项目。 此外，光合作用研究中涉及的概念被用来丰富他在物理化学和生物化学方面的教学。 例如，PI教授生物纳米技术课程，作为亚利桑那州立大学学习社区项目的一部分，学生们探索纳米技术的科学，政策和社会学。 PI也是NSF IGERT生物分子纳米技术项目的负责人。 光合反应中心是纳米级光电器件的一个重要例子，这项工作的概念是IGERT学生研究的生物分子纳米技术的关键例子之一。 PI也是ASU生物能源研究计划的现任主任，该计划是从ASU光合作用中心发展出来的一项新计划，旨在利用我们对光合作用过程的不断了解，并将其用于开发新能源和能量转换手段。 最后，PI指导生物设计研究所的生物光学纳米技术中心。 在这个角色中，他直接与大量的私人，商业和公民团体进行交流，这些讨论构成了社区嵌入式研究的新方法的基础，其中社会的需求和发现的过程被整合到跨学科研究的新混合模式中。该项目由生物科学理事会分子和细胞生物科学部的分子生物物理学和数学和物理科学理事会化学部的实验物理化学计划共同支持。