Shan Jianyu, Niedzwiedzki Dariusz M, Tomar Rupal S, Liu Zhenfeng, Liu Haijun
Key Laboratory of Biomacromolecules (CAS), National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.
College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China.
Sci Adv. 2024 Dec 13;10(50):eadq9967. doi: 10.1126/sciadv.adq9967.
Photosystem II (PSII) splits water in oxygenic photosynthesis on Earth. The structure and function of the CSM-type PSII-LHCII (light-harvesting complex II) megacomplexes from the wild-type and PsbR-deletion mutant plants are studied through electron microscopy (EM), structural mass spectrometry, and ultrafast fluorescence spectroscopy [time-resolved fluorescence (TRF)]. The cryo-EM structure of a type I CSM megacomplex demonstrates that the three domains of PsbR bind to the stromal side of D1, D2, and CP43; associate with the single transmembrane helix of the redox active Cyt ; and stabilize the luminal extrinsic PsbP, respectively. This megacomplex, with PsbR and PsbY centered around the narrow interface between two dimeric PSII cores, provides the supramolecular structural basis that regulates the plastoquinone occupancy in Q site, excitation energy transfer, and oxygen evolution. PSII-LHCII megacomplexes (types I and II) and LHC aggregation levels in mutant were also interrogated and compared to wild-type plants through EM and picosecond TRF.
在地球上的氧光合作用中，光系统II（PSII）负责分解水。通过电子显微镜（EM）、结构质谱和超快荧光光谱[时间分辨荧光（TRF）]，研究了野生型和PsbR缺失突变体植物中CSM型PSII-LHCII（光捕获复合物II）超大复合物的结构和功能。I型CSM超大复合物的冷冻电镜结构表明，PsbR的三个结构域分别与D1、D2和CP43的基质侧结合；与氧化还原活性细胞色素的单个跨膜螺旋相关联；并稳定腔外的PsbP。这种以PsbR和PsbY为中心、位于两个二聚体PSII核心之间狭窄界面周围的超大复合物，提供了调节醌在Q位点的占据、激发能量转移和氧气释放的超分子结构基础。还通过EM和皮秒TRF对突变体中的PSII-LHCII超大复合物（I型和II型）和LHC聚集水平进行了检测，并与野生型植物进行了比较。
