Resolution and Reconstitution of Photosystem I in Cyanobacteria and Higher Plants: Molecular Biological and Physicochemical Studies

这项研究计划旨在了解蓝藻和绿色植物中光系统I反应中心的结构、功能和组织。到目前为止取得的进展包括在A1位引入替代苯二酚的生物学方法，确定对称位置的电子转移辅助因子之间的电子转移是单向还是双向的实验方法，以及确定自由结合的PsaC的三维核磁共振溶液结构。这结合从X射线结晶学获得的关于原子的三维空间排列的新结构信息和从磁共振光谱获得的辅因子中的电子自旋密度分布，为PS I的研究开辟了新的途径。其一是替代苯二酚生物掺入A1位的效应，用于研究Gibbs自由能变化对正向和反向电子转移速率的影响，以及A1-受体内电子密度分布的研究。另一个是PsaA、PsaB、PsaC和PsaD亚基之间在分子水平上的蛋白质-蛋白质相互作用，特别是当PSAC与其在PS I中的蛋白质伙伴对接时发生的二级结构的变化。目的是确定这些蛋白质之间发生的动态相互作用，以产生一个功能性PS I复合体。这些研究有望对赋予有机辅因子氧化还原特性的蛋白质因素的理解以及对多组分、膜结合的复合体组装中蛋白质-蛋白质相互作用的理解产生影响。因此，这项工作的意义应该远远超出氧合光合作用的领域

This research program aims at understanding the structure,function and organization of the Photosystem I reaction center in cyanobacteria and green plants.The advances made so far include a biological method to introduce alternative quinones into the A1site,an experimental approach to determine whether electron transfer is uni-or bi-directional among the symmetrically-located electron transfer cofactors,and a determination of the 3-dimensional NMR solution structure of unbound PsaC.This,combined with newly-available structural information about the 3-dimensional spatial arrangement of atoms from X-ray crystallography and the electron spin density distribution in cofactors from magnetic resonance spectroscopy,has opened new avenues for research in PS I. One is the effect of biological incorporation of alternative quinones into the A1 site for studies of the effect of Gibbs free energy changes on rates of forward and backward electron transfer, and for studies of the electron density distribution within the A1 - acceptor. Another is the protein-protein interactions at the molecular level between the PsaA,PsaB, PsaC,and PsaD subunits,and focuses especially on the changes in secondary structure that take place when PsaC docks with its protein partners in PS I.The goal is to determine the dynamic interactions that occur among these to produce a functional PS I complex.These studies promise to have an impact on the understanding of protein factors responsible for conferring redox properties to organic cofactors and on the understanding of protein-protein interactions in the assembly of multi-component,membrane-bound complexes.Hence,this work should have relevance well beyond the realm of oxygenic photosynthesis