Structural insights into the unusual core photocomplex from a triply extremophilic purple bacterium,Halorhodospira halochloris  

作　　者：Chen-Hui Qi Guang-Lei Wang Fang-Fang Wang Jie Wang Xiang-Ping Wang Mei-Juan Zou Fei Ma Michael T.Madigan Yukihiro Kimura Zheng-Yu Wang-Otomo Long-Jiang Yu 

机构地区：[1]Key Laboratory of Photobiology,Photosynthesis Research Center,Institute of Botany,Chinese Academy of Sciences,Beijing 100093,China [2]University of Chinese Academy of Sciences,Beijing 100049,China [3]Zhangjiang Lab,National Facility for Protein Science in Shanghai,Shanghai Advanced Research Institute,Chinese Academy of Sciences,Shanghai 201210,China [4]Department of Microbiology,School of Biological Sciences,Southern Illinois University,Carbondale,IL 62901,USA [5]Department of Agrobioscience,Graduate School of Agricultural Science,Kobe University,Nada,Kobe 657-8501,Japan [6]Faculty of Science,Ibaraki University,Mito 310-8512,Japan

出　　处：《Journal of Integrative Plant Biology》2024年第10期2262-2272,共11页植物学报（英文版）

基　　金：supported in part by the National Key R&D Program of China(No.2022YFC3401800);National Natural Science Foundation of China(32070264);Shandong Provincial Natural Science Foundation(ZR2019ZD48);the Strategic Priority Research Program of CAS(XDA26050402);the Science&Technology Specific Project in Agricultural High-tech Industrial Demonstration Area of the Yellow River Delta(2022SZX12);the Innovation Center for Academicians of Hainan Province;the Specific Research Fund of the Innovation Center for Academicians of Hainan Province(No.YSPTZX202309);supported in part by NASA Cooperative Agreement 80NSSC21M0355。

摘　　要：Halorhodospira(Hlr.)halochloris is a triply extremophilic phototrophic purple sulfur bacterium,as it is thermophilic,alkaliphilic,and extremely halophilic.The light-harvesting-reaction center(LH1–RC)core complex of this bacterium displays an LH1-Q_(y)transition at 1,016 nm,which is the lowest-energy wavelength absorption among all known phototrophs.Here we report the cryo-EM structure of the LH1–RC at 2.42?resolution.The LH1 complex forms a tricyclic ring structure composed of 16αβγ-polypeptides and oneαβ-heterodimer around the RC.From the cryo-EM density map,two previously unrecognized integral membrane proteins,referred to as protein G and protein Q,were identified.Both of these proteins are single transmembrane-spanning helices located between the LH1 ring and the RC Lsubunit and are absent from the LH1–RC complexes of all other purple bacteria of which the structures have been determined so far.Besides bacteriochlorophyll b molecules(B1020)located on the periplasmic side of the Hlr.halochloris membrane,there are also two arrays of bacteriochlorophyll b molecules(B800 and B820)located on the cytoplasmic side.Only a single copy of a carotenoid(lycopene)was resolved in the Hlr.halochloris LH1–α3β3 and this was positioned within the complex.The potential quinone channel should be the space between the LH1–α3β3 that accommodates the single lycopene but does not contain aγ-polypeptide,B800 and B820.Our results provide a structural explanation for the unusual Q_(y)red shift and carotenoid absorption in the Hlr.halochloris spectrum and reveal new insights into photosynthetic mechanisms employed by a species that thrives under the harshest conditions of any phototrophic microorganism known.

关 键 词：CRYO-EM LH1-RC single carotenoid three bacteriochlorophyll b molecules triply extremophilic purple bacterium unusual Qy red shift 

分 类 号：Q945.11[生物学—植物学]