Structure and Function of Supercomplexes of Photosystem I with its Peripheral Antenna Systems in Green Algae and Cyanobacteria

光合作用是地球上将来自太阳的光能转化为生物有机体可获得的化学能的主要过程。光合作用的产物最终为地球上所有高等生物提供能量，并在大气中产生所有氧气。本项目的目的是揭示大分子太阳能转换光系统I(PSI)的结构和功能，并确定其外围天线系统在真核生物(植物和绿藻)和原核生物(蓝藻)中的相互作用。光系统I复合体由12-14个蛋白质组成，120多个辅因子(叶绿素和类胡萝卜素)与之结合。此外，光系统I被动态地耦合到附加的外围天线系统，以进一步提高光捕获的效率。该项目旨在揭示植物型光系统I与光捕获复合体I的超复合体中的结构和功能，以及蓝藻光系统I在其具有18个ISIA蛋白质的超复合体中的结构和功能。该项目的总体目标是确定植物型和蓝藻光系统I中的光系统I-天线超复合体的结构。实验装置包括通过X射线结构分析进行结晶和结构确定，通过诱变设计结构和功能改进的复合体，以及通过时间分辨光谱进行功能研究。该项目将导致对原核生物和真核生物光合作用系统的结构组织的详细了解，并将揭示外部天线复合体与光合作用核心单位的功能耦合。此外，该项目将为膜蛋白形成大型超复合体过程中的蛋白质组装提供新的见解。更广泛的影响了解巨型光系统I超复合体结构的原子细节将促进我们对生物-太阳能转换基本过程的机制的理解。此外，这将有助于阐明超复合体中光合作用反应中心及其外围天线之间的结构-功能关系，这些关系决定了生物太阳能系统中的能量转换比人工系统中更高的效率和灵活性。因此，该项目将为开发模拟自然的太阳能转换器的新概念提供广泛的影响。此外，对光合作用过程的基本了解可以使植物的光合作用能力增强，对多种环境胁迫的耐受性增强。该项目的目的之一是利用所获得的知识，提高学生揭示自然能源转换秘密的兴趣，并增强他们学习科学的动机。该项目还将提供一个机会，让公众了解这一令人兴奋的领域的最新发现。

Photosynthesis is the main process on Earth that converts light energy from the sun into chemical energy accessible for living organisms. The products of photosynthesis ultimately provide all higher life on earth with energy and produce all oxygen in the atmosphere. The aim of this project is to unravel the structure and function of the large molecular solar energy converter Photosystem I (PSI) and to determine the interaction of its peripheral antenna systems in eukaryotes (plants and green algae) and prokaryotes (cyanobacteria). The photosystem I complex consists of 12-14 proteins to which more than 120 cofactors (chlorophylls and carotenoids) are bound. Furthermore, photosystem I is dynamically coupled to additional peripheral antenna systems to further increase the efficiency of light capturing. The project aims to unravel the structure and function of both the plant-type photosystem I in a supercomplex with the light harvesting complex I and the cyanobacterial photosystem I in its supercomplex with 18 IsiA proteins. The overall goal of the project is the determination of the structure of both photosystem I-antenna supercomplexes in plant-type and cyanobacterial photosystem I. The experimental setup includes crystallization and structure-determination by X-ray structure analysis, the design of structurally and functionally improved complexes by mutagenesis and functional investigations by time-resolved spectroscopy. The project will lead to detailed insights into the structural organization of the photosynthetic system in prokaryotes and eukaryotes and will unravel the functional coupling of the external antenna complexes to the core units of photosynthesis. Furthermore the project will provide new insights into protein assembly during the formation of large supercomplexes of membrane proteins. Broader ImpactsKnowledge of the atomic details of the structure of giant Photosystem I supercomplexes will boost our understanding of the mechanisms of basic processes of bio-solar energy conversion. Moreover, this will help to elucidate structure-functional relationships between the photosynthetic reaction centers and their peripheral antennas in the supercomplexes that determine a higher efficiency and flexibility of the energy conversion in the bio-solar systems than in man-made systems. The project will thereby provide broad impacts for the development of new concepts for solar energy converters that mimic nature. Furthermore, fundamental understanding of the photosynthetic processes could lead to the development of plants with enhanced photosynthetic ability and increased tolerance to many kinds of environmental stress. One of the aims of the project is to use gained knowledge for boosting students' interest in revealing the secrets of natural energy conversion and enhancing their motivation in studying science. The project will also give an opportunity to inform the public on recent discoveries in this exciting area.