Structure and Function of Type I Reaction Centers: Photosystem I and Green Bacteria

对光系统1及其密切相关的绿硫菌光合反应中心的结构和功能进行研究。该项目将重点关注FeS中心和醌作为电子转移的瞬态中间体的作用。闪光动力学分光光度法和EPR光谱法将作为主要的分析方法。在绿色细菌的情况下，我们将用22 kDa的含有大肠杆菌中表达的多肽的FeS重组受体侧。阐明光系统1中醌结合位点的抑制机制是重要的，因为该位点有可能用于开发一类新的除草剂。在核心异二聚体的分子模型研究之后，一个新的项目开始了光系统1。该实验室已经测试了一个由该模型产生的关于PsaC亚基与核心异源二聚体中的Fx结构域相互作用的假设。这将继续与亮氨酸拉链图案的作用的直接实验测试。这将包括合成含有基序的肽并研究它们的物理性质。未来的实验将通过合成设计的折叠成4-的蛋白质来创建光系统1的模型。-螺旋束，并在螺旋环中安装与光系统1相关的氧化还原中心。这一举措将为未来研究含有光活性成分的模型提供立足点。光合作用在植物和某些细菌中是通过光与含有金属-蛋白质复合物的特殊色素的相互作用来完成的。该方案将采用复杂的分析方法分析复合物的组成和金属、色素和蛋白质的比例。此外，某些化合物与该复合物相互作用的性质对于设计干扰光合作用的除草剂具有重要意义。

Support is requested to investigate the structure and function of photosynthetic reaction centers in photosystem 1 and the closely related green sulfur bacteria. The project will focus on the role of FeS centers and quinones as transient intermediates in electron transfer. Flash kinetic spectrophotometry and EPR spectroscopy will be used as principle analytical methods. In the case of green bacteria we will reconstitute the acceptor side with a 22 kDa FeS containing polypeptide that has been expressed in E. coli. Elucidation of the mechanism of inhibition of the quinone binding site in Photosystem 1 is important because of the potential of using this site for a new class of herbicides. A new project has been initiated on Photosystem 1 following a molecular modeling study of the core heterodimer. The lab has already tested one hypothesis generated by the modeling concerning the interaction of the subunit PsaC with the Fx domain in the core heterodimer. This will be continued together with a direct experimental test of the role of the leucine zipper motif. This will involve synthesis of peptides containing the motif and studying their physical properties. Future experiments will create models of Photosystem 1 by synthesizing designed proteins that fold into 4-.-helical bundles and installing redox centers of relevance to Photosystem 1 in the interhelical loops. This initiative will provide footholds for future studies of models that would contain photoactive components. %%% Photosynthesis is accomplished in plant and certain bacteria by the interaction of light with specialized pigment containing metal-protein complexes. The components of the complex and the ration of metal, pigment, and protein are to be analyzed in the proposal by sophisticated analytical methods. Also, the nature of the interaction of certain chemical compounds with the complex is important as a model for the design of herbicides that can interfere with photosynthesis.