National Laboratory of Biomacromolecules, CAS Centre for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.
College of Life Science, Capital Normal University, Beijing, China.
Nat Plants. 2021 Aug;7(8):1119-1131. doi: 10.1038/s41477-021-00960-8. Epub 2021 Jul 8.
In green algae and plants, state transitions serve as a short-term light-acclimation process in the regulation of the light-harvesting capacity of photosystems I and II (PSI and PSII, respectively). During the process, a portion of light-harvesting complex II (LHCII) is phosphorylated, dissociated from PSII and binds with PSI to form the supercomplex PSI-LHCI-LHCII. Here, we report high-resolution structures of PSI-LHCI-LHCII from Chlamydomonas reinhardtii, revealing the mechanism of assembly between the PSI-LHCI complex and two phosphorylated LHCII trimers containing all four types of LhcbM protein. Two specific LhcbM isoforms, namely LhcbM1 and LhcbM5, directly interact with the PSI core through their phosphorylated amino terminal regions. Furthermore, biochemical and functional studies on mutant strains lacking either LhcbM1 or LhcbM5 indicate that only LhcbM5 is indispensable in supercomplex formation. The results unravel the specific interactions and potential excitation energy transfer routes between green algal PSI and two phosphorylated LHCIIs.
在绿藻和植物中，状态转换是一种短期的光适应过程，用于调节光系统 I 和光系统 II（分别为 PSI 和 PSII）的光捕获能力。在此过程中，一部分光捕获复合物 II（LHCII）发生磷酸化，从 PSII 上解离下来并与 PSI 结合形成 PSI-LHCI-LHCII 超复合物。在这里，我们报道了莱茵衣藻 PSI-LHCI-LHCII 的高分辨率结构，揭示了 PSI-LHCI 复合物与两个含有所有四种 LhcbM 蛋白的磷酸化 LHCII 三聚体之间的组装机制。两种特定的 LhcbM 同工型，即 LhcbM1 和 LhcbM5，通过其磷酸化的氨基末端区域直接与 PSI 核心相互作用。此外，对缺失 LhcbM1 或 LhcbM5 的突变株进行的生化和功能研究表明，只有 LhcbM5 对于超复合物的形成是不可或缺的。这些结果揭示了绿藻 PSI 和两个磷酸化 LHCII 之间的特定相互作用和潜在的激发能量转移途径。
