Structure and function of photosystem I related supercomplexes in Chlamydomonas reinhardtii

在这里，我们的目标是解决光系统I(PSI)超复合体的动态重构问题。这些超复合体在PSI与其相关的捕光蛋白(LHCI)之间、PSI-LHCI与光系统II的捕光蛋白(LHCII)之间以及两个PSI-LHCI单体之间形成PSI二聚体。此外，还可以形成PSI-LHCI Cyt b6f超络合物。目前应用的重点将是LHCA2、LHCA9、PSAG和PSAH在PSI-LHCI-LHCI、PSI-LHCI二聚体以及PSI-LHCI细胞b6f超复合物形成中的作用及其对PSI受体侧电子分配、状态转变和光合作用电子流效率的调节。该提议的另一个目的是分离PSI-LHCI Cyt b6f超络合物，并通过冷冻-EM分析确定其结构。我们还将使用冷冻-ET技术，目的是在体内显示PSI-LHCI二聚体以及PSI-LHCI细胞b6f超复合体。此外，我们的目标是用冷冻电子显微镜确定PSI-LHCI-CytC6配合物的结构。这一点特别令人感兴趣，因为与真核生物的质蓝蛋白(PC)相比，真核细胞色素c6更类似于蓝藻的电子供体。因此，PSI-LHCI-Cytc6复合体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藻和维管植物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.