Christianson Bern, Liu Zekun, Zhang Yingyue, Wang Chen, Gardner Adrian M, Zhang Yu-Zhong, Wang Peng, Liu Lu-Ning
Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool, UK.
MOE Key Laboratory of Evolution and Marine Biodiversity, Frontiers Science Center for Deep Ocean Multispheres and Earth System & College of Marine Life Sciences, Ocean University of China, Qingdao, China.
Physiol Plant. 2025 May-Jun;177(3):e70275. doi: 10.1111/ppl.70275.
Photosynthetic reaction center-light harvesting 1 (RC-LH1) core supercomplexes are essential for energy capture and electron transport in purple bacteria. Rhodospirillum rubrum, a model organism for bacterial photosynthesis, features an RC-LH1 architecture with a closed LH1 ring and lacks the peripheral LH2 antenna in the photosynthetic membranes. How this unique RC-LH1 supercomplex performs energy transfer and quinone transport remains unclear. Here, we characterized both the structural and functional properties of Rsp. rubrum RC-LH1 supercomplex using cryo-electron microscopy (cryo-EM), transient absorption (TA) spectroscopy, and cytochrome c oxidation assays. Cryo-EM of the RC-LH1 monomeric structure revealed a closed LH1 ring of 16 αβ-polypeptides encircling the RC, with weaker RC-LH1 interactions than other RC-LH1 structures reported. TA spectra and cytochrome c oxidation assays showed that Rsp. rubrum RC-LH1 monomer with a closed LH1 ring exhibits slower and more distributed excitation energy transfer (EET) kinetics from LH1 to RC and slower electron transport rates than Rba. sphaeroides RC-LH1 monomer with a large opening in the LH1 ring. Our findings provide insight into the unique architecture and spectroscopic properties of Rsp. rubrum RC-LH1 supercomplex. This study enhances our understanding of bacterial photosynthetic mechanisms and lays the foundation for bioengineering applications in artificial photosynthetic systems.
光合反应中心 - 捕光1（RC - LH1）核心超复合物对于紫色细菌中的能量捕获和电子传递至关重要。红螺菌是细菌光合作用的模式生物，其光合膜中的RC - LH1结构具有封闭的LH1环且缺乏外周LH2天线。这种独特的RC - LH1超复合物如何进行能量转移和醌运输仍不清楚。在这里，我们使用冷冻电子显微镜（cryo - EM）、瞬态吸收（TA）光谱和细胞色素c氧化测定来表征红螺菌RC - LH1超复合物的结构和功能特性。RC - LH1单体结构的冷冻电子显微镜显示，一个由16个αβ多肽组成的封闭LH1环围绕着RC，与报道的其他RC - LH1结构相比，RC - LH1相互作用较弱。TA光谱和细胞色素c氧化测定表明，具有封闭LH1环的红螺菌RC - LH1单体与具有LH1环大开口的球形红杆菌RC - LH1单体相比，从LH1到RC的激发能量转移（EET）动力学更慢且分布更广，电子传输速率也更慢。我们的研究结果为红螺菌RC - LH1超复合物的独特结构和光谱特性提供了见解。这项研究增进了我们对细菌光合机制的理解，并为人工光合系统中的生物工程应用奠定了基础。
