Structure and function of photosystem I related supercomplexes in Chlamydomonas reinhardtii

本文旨在研究光系统I（PSI）超复合物在C.莱因哈德氏菌这些超复合物在PSI和其相关的捕光蛋白（LHCI）之间、在状态转换期间PSI-LHCI和光系统II（LHCII）的捕光蛋白之间以及在两个PSI-LHCI单体之间形成以构成PSI二聚体。此外，可以形成PSI-LHCI Cyt b6 f超复合物。本申请的重点将是LHCA 2、LHCA 9、PSAG和PSAH在PSI-LHCI-LHCII、PSI-LHCI二聚体以及PSI-LHCI Cyt b6 f超复合物形成中的作用及其对PSI受体侧电子分配、状态转换和光合电子流效率的调节的后果。该提案的另一个目的是分离PSI-LHCI Cyt b6 f超复合物并通过冷冻EM分析确定结构。我们还将采用冷冻ET，目的是在体内可视化PSI-LHCI二聚体以及PSI-LHCI Cyt b6 f超复合物。此外，我们的目标是确定PSI-LHCI-Cyt c6复合物的结构，通过冷冻电镜。这一点特别令人感兴趣，因为与真核质蓝蛋白（PC）相比，真核细胞Cyt c6更类似于蓝细菌电子供体。因此，PSI-LHCI-Cyt c6复合物的结构将使我们深入了解进化中间体的结合，这可以很容易地与已知的衣原体和维管植物PSI-LHCI-PC结构进行比较。

Herein we aim to address the dynamic remodeling of photosystem I (PSI) supercomplexes in C. reinhardtii. These supercomplexes are formed between PSI and its associated light-harvesting proteins (LHCI), between PSI-LHCI and light-harvesting proteins of photosystem II (LHCII) during state transitions as well as between two PSI-LHCI monomers to constitute a PSI dimer. In addition, PSI-LHCI Cyt b6f supercomplexes can be formed. A focus of the current application will be on the role of LHCA2, LHCA9, PSAG, and PSAH in PSI-LHCI-LHCII, PSI-LHCI dimer as well as in PSI-LHCI Cyt b6f supercomplex formation and its consequences for regulation of electron partitioning at the PSI acceptor side, state transitions and the efficiency of photosynthetic electron flow. Another aim of the proposal is to isolate PSI-LHCI Cyt b6f supercomplexes and determine the structure by cryo-EM analyses. We will also employ cryo-ET with the aim to visualize PSI-LHCI dimer as well as in PSI-LHCI Cyt b6f supercomplexes in vivo. Moreover, we aim to determine the structure of PSI-LHCI-Cyt c6 complexes by cryo-EM. This is of particular interest, as eukaryotic Cyt c6 is more similar to cyanobacterial electron donors compared to eukaryotic plastocyanin (PC). Therefore, the structure of PSI-LHCI-Cyt c6 complexes would give us insights into the binding of an evolutionary intermediate, which could be readily compared with the known Chlamydomonas and vascular plant PSI-LHCI-PC structures.