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

研究光系统1和与之密切相关的绿色硫磺细菌的光合作用反应中心的结构和功能需要支持。该项目将侧重于FeS中心和苯二酚在电子转移中作为瞬时中间体的作用。闪光动力学分光光度法和EPR光谱分析将是主要的分析方法。在绿色细菌的情况下，我们将用在大肠杆菌中表达的含有22 kDa FES的多肽来重组受体侧。阐明光系统1中苯醌结合位点的抑制机制是很重要的，因为该位点有可能用于一类新的除草剂。在对核心杂二聚体进行分子模拟研究后，在光系统1上启动了一个新的项目。实验室已经测试了通过建模产生的一个假设，该假设涉及核心异二聚体中PSAC亚基与FX结构域的相互作用。这将继续与亮氨酸拉链基序的作用的直接实验测试一起进行。这将包括合成含有该基序的多肽并研究它们的物理性质。未来的实验将通过合成折叠成4螺旋束的设计蛋白质，并在螺旋间环中安装与光系统1相关的氧化还原中心来创建光系统1的模型。这一倡议将为未来对含有光活性成分的模型的研究提供立足点。在植物和某些细菌中，光合作用是通过光与含有金属-蛋白质络合物的特殊色素相互作用而完成的。在建议书中，将用复杂的分析方法分析络合物的组成以及金属、色素和蛋白质的比例。此外，某些化合物与络合物相互作用的性质对于设计干扰光合作用的除草剂是很重要的。

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.