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Yan YH, Wang GL, Yue XY, Ma F, Madigan MT, Wang-Otomo ZY, Zou MJ, Yu LJ. Molecular structure and characterization of the Thermochromatium tepidum light-harvesting 1 photocomplex produced in a foreign host. BIOCHIMICA ET BIOPHYSICA ACTA. BIOENERGETICS 2024; 1865:149050. [PMID: 38806091 DOI: 10.1016/j.bbabio.2024.149050] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2024] [Revised: 05/15/2024] [Accepted: 05/21/2024] [Indexed: 05/30/2024]
Abstract
Purple phototrophic bacteria possess light-harvesting 1 and reaction center (LH1-RC) core complexes that play a key role in converting solar energy to chemical energy. High-resolution structures of LH1-RC and RC complexes have been intensively studied and have yielded critical insight into the architecture and interactions of their proteins, pigments, and cofactors. Nevertheless, a detailed picture of the structure and assembly of LH1-only complexes is lacking due to the intimate association between LH1 and the RC. To study the intrinsic properties and structure of an LH1-only complex, a genetic system was constructed to express the Thermochromatium (Tch.) tepidum LH1 complex heterologously in a modified Rhodospirillum rubrum mutant strain. The heterologously expressed Tch. tepidum LH1 complex was isolated in a pure form free of the RC and exhibited the characteristic absorption properties of Tch. tepidum. Cryo-EM structures of the LH1-only complexes revealed a closed circular ring consisting of either 14 or 15 αβ-subunits, making it the smallest completely closed LH1 complex discovered thus far. Surprisingly, the Tch. tepidum LH1-only complex displayed even higher thermostability than that of the native LH1-RC complex. These results reveal previously unsuspected plasticity of the LH1 complex, provide new insights into the structure and assembly of the LH1-RC complex, and show how molecular genetics can be exploited to study membrane proteins from phototrophic organisms whose genetic manipulation is not yet possible.
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Affiliation(s)
- Yi-Hao Yan
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Guang-Lei Wang
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xing-Yu Yue
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Fei Ma
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | - Michael T Madigan
- School of Biological Sciences, Department of Microbiology, Southern Illinois University, Carbondale, IL 62901, USA
| | | | - Mei-Juan Zou
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China.
| | - Long-Jiang Yu
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China; University of Chinese Academy of Sciences, Beijing 100049, China.
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2
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Martin EC, Bowie AG, Wellfare Reid T, Neil Hunter C, Hitchcock A, Swainsbury DJ. Sulfoquinovosyl diacylglycerol is required for dimerisation of the Rhodobacter sphaeroides reaction centre-light harvesting 1 core complex. Biochem J 2024; 481:823-838. [PMID: 38780411 PMCID: PMC11346425 DOI: 10.1042/bcj20240125] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2024] [Revised: 05/22/2024] [Accepted: 05/23/2024] [Indexed: 05/25/2024]
Abstract
The reaction centre-light harvesting 1 (RC-LH1) core complex is indispensable for anoxygenic photosynthesis. In the purple bacterium Rhodobacter (Rba.) sphaeroides RC-LH1 is produced both as a monomer, in which 14 LH1 subunits form a C-shaped antenna around 1 RC, and as a dimer, where 28 LH1 subunits form an S-shaped antenna surrounding 2 RCs. Alongside the five RC and LH1 subunits, an additional polypeptide known as PufX provides an interface for dimerisation and also prevents LH1 ring closure, introducing a channel for quinone exchange that is essential for photoheterotrophic growth. Structures of Rba. sphaeroides RC-LH1 complexes revealed several new components; protein-Y, which helps to form the quinone channel; protein-Z, of unknown function and seemingly unique to dimers; and a tightly bound sulfoquinovosyl diacylglycerol (SQDG) lipid that interacts with two PufX arginine residues. This lipid lies at the dimer interface alongside weak density for a second molecule, previously proposed to be an ornithine lipid. In this work we have generated strains of Rba. sphaeroides lacking protein-Y, protein-Z, SQDG or ornithine lipids to assess the roles of these previously unknown components in the assembly and activity of RC-LH1. We show that whilst the removal of either protein-Y, protein-Z or ornithine lipids has only subtle effects, SQDG is essential for the formation of RC-LH1 dimers but its absence has no functional effect on the monomeric complex.
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Affiliation(s)
- Elizabeth C. Martin
- Plants, Photosynthesis and Soil, School of Bioscience, University of Sheffield, Sheffield, U.K
| | - Adam G.M. Bowie
- Plants, Photosynthesis and Soil, School of Bioscience, University of Sheffield, Sheffield, U.K
| | - Taylor Wellfare Reid
- Plants, Photosynthesis and Soil, School of Bioscience, University of Sheffield, Sheffield, U.K
| | - C. Neil Hunter
- Plants, Photosynthesis and Soil, School of Bioscience, University of Sheffield, Sheffield, U.K
| | - Andrew Hitchcock
- Plants, Photosynthesis and Soil, School of Bioscience, University of Sheffield, Sheffield, U.K
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3
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Hao JF, Qi CH, Yu BY, Wang HY, Gao RY, Yamano N, Ma F, Wang P, Xin YY, Zhang CF, Yu LJ, Zhang JP. Light-Quality-Adapted Carotenoid Photoprotection in the Photosystem of Roseiflexus castenholzii. J Phys Chem Lett 2024:3470-3477. [PMID: 38512331 DOI: 10.1021/acs.jpclett.4c00593] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/22/2024]
Abstract
The photosystem of filamentous anoxygenic phototroph Roseiflexus (Rfl.) castenholzii comprises a light-harvesting (LH) complex encircling a reaction center (RC), which intensely absorbs blue-green light by carotenoid (Car) and near-infrared light by bacteriochlorophyll (BChl). To explore the influence of light quality (color) on the photosynthetic activity, we compared the pigment compositions and triplet excitation dynamics of the LH-RCs from Rfl. castenholzii was adapted to blue-green light (bg-LH-RC) and to near-infrared light (nir-LH-RC). Both LH-RCs bind γ-carotene derivatives; however, compared to that of nir-LH-RC (12%), bg-LH-RC contains substantially higher keto-γ-carotene content (43%) and shows considerably faster BChl-to-Car triplet excitation transfer (10.9 ns vs 15.0 ns). For bg-LH-RC, but not nir-LH-RC, selective photoexcitation of Car and the 800 nm-absorbing BChl led to Car-to-Car triplet transfer and BChl-Car singlet fission reactions, respectively. The unique excitation dynamics of bg-LH-RC enhances its photoprotection, which is crucial for the survival of aquatic anoxygenic phototrophs from photooxidative stress.
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Affiliation(s)
- Jin-Fang Hao
- Key Laboratory of Advanced Light Conversion Materials and Biophotonics, Department of Chemistry, Renmin University of China, Beijing 100872, P. R. China
| | - Chen-Hui Qi
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, P. R. China
| | - Bu-Yang Yu
- National Laboratory of Solid State Microstructures & School of Physics, Nanjing University, Nanjing 210093, China
| | - Hao-Yi Wang
- Key Laboratory of Advanced Light Conversion Materials and Biophotonics, Department of Chemistry, Renmin University of China, Beijing 100872, P. R. China
| | - Rong-Yao Gao
- Key Laboratory of Advanced Light Conversion Materials and Biophotonics, Department of Chemistry, Renmin University of China, Beijing 100872, P. R. China
| | - Nami Yamano
- Key Laboratory of Advanced Light Conversion Materials and Biophotonics, Department of Chemistry, Renmin University of China, Beijing 100872, P. R. China
| | - Fei Ma
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, P. R. China
| | - Peng Wang
- Key Laboratory of Advanced Light Conversion Materials and Biophotonics, Department of Chemistry, Renmin University of China, Beijing 100872, P. R. China
| | - Yue-Yong Xin
- Hangzhou Normal University, 2318 Yuhangtang Road, Cangqian, Yuhang District, Hangzhou 311121, Zhejiang, China
| | - Chun-Feng Zhang
- National Laboratory of Solid State Microstructures & School of Physics, Nanjing University, Nanjing 210093, China
| | - Long-Jiang Yu
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, P. R. China
| | - Jian-Ping Zhang
- Key Laboratory of Advanced Light Conversion Materials and Biophotonics, Department of Chemistry, Renmin University of China, Beijing 100872, P. R. China
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4
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Qi CH, Wang GL, Wang FF, Wang J, Wang XP, Zou MJ, Ma F, Madigan MT, Kimura Y, Wang-Otomo ZY, Yu LJ. Structural insights into the unusual core photocomplex from a triply extremophilic purple bacterium, Halorhodospira halochloris. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2024. [PMID: 38411333 DOI: 10.1111/jipb.13628] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2023] [Revised: 01/17/2024] [Accepted: 02/03/2024] [Indexed: 02/28/2024]
Abstract
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-Qy 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 Å resolution. The LH1 complex forms a tricyclic ring structure composed of 16 αβγ-polypeptides and one αβ-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 L-subunit 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 a γ-polypeptide, B800 and B820. Our results provide a structural explanation for the unusual Qy 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.
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Affiliation(s)
- Chen-Hui Qi
- Key Laboratory of Photobiology, Photosynthesis Research Center, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Guang-Lei Wang
- Key Laboratory of Photobiology, Photosynthesis Research Center, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Fang-Fang Wang
- Zhangjiang Lab, National Facility for Protein Science in Shanghai, Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai, 201210, China
| | - Jie Wang
- Key Laboratory of Photobiology, Photosynthesis Research Center, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Xiang-Ping Wang
- Key Laboratory of Photobiology, Photosynthesis Research Center, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Mei-Juan Zou
- Key Laboratory of Photobiology, Photosynthesis Research Center, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China
| | - Fei Ma
- Key Laboratory of Photobiology, Photosynthesis Research Center, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China
| | - Michael T Madigan
- Department of Microbiology, School of Biological Sciences, Southern Illinois University, Carbondale, IL, 62901, USA
| | - Yukihiro Kimura
- Department of Agrobioscience, Graduate School of Agricultural Science, Kobe University, Nada, Kobe, 657-8501, Japan
| | | | - Long-Jiang Yu
- Key Laboratory of Photobiology, Photosynthesis Research Center, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China
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5
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Yu L, Min Z, Liu M, Xin Y, Liu A, Kuang J, Wu W, Wu J, He H, Xin J, Blankenship RE, Tian C, Xu X. A cytochrome c 551 mediates the cyclic electron transport chain of the anoxygenic phototrophic bacterium Roseiflexus castenholzii. PLANT COMMUNICATIONS 2024; 5:100715. [PMID: 37710959 PMCID: PMC10873879 DOI: 10.1016/j.xplc.2023.100715] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Revised: 06/27/2023] [Accepted: 09/08/2023] [Indexed: 09/16/2023]
Abstract
Roseiflexus castenholzii is a gram-negative filamentous phototrophic bacterium that carries out anoxygenic photosynthesis through a cyclic electron transport chain (ETC). The ETC is composed of a reaction center (RC)-light-harvesting (LH) complex (rcRC-LH); an alternative complex III (rcACIII), which functionally replaces the cytochrome bc1/b6f complex; and the periplasmic electron acceptor auracyanin (rcAc). Although compositionally and structurally different from the bc1/b6f complex, rcACIII plays similar essential roles in oxidizing menaquinol and transferring electrons to the rcAc. However, rcACIII-mediated electron transfer (which includes both an intraprotein route and a downstream route) has not been clearly elucidated, nor have the details of cyclic ETC. Here, we identify a previously unknown monoheme cytochrome c (cyt c551) as a novel periplasmic electron acceptor of rcACIII. It reduces the light-excited rcRC-LH to complete a cyclic ETC. We also reveal the molecular mechanisms involved in the ETC using electron paramagnetic resonance (EPR), spectroelectrochemistry, and enzymatic and structural analyses. We find that electrons released from rcACIII-oxidized menaquinol are transferred to two alternative periplasmic electron acceptors (rcAc and cyt c551), which eventually reduce the rcRC to form the complete cyclic ETC. This work serves as a foundation for further studies of ACIII-mediated electron transfer in anoxygenic photosynthesis and broadens our understanding of the diversity and molecular evolution of prokaryotic ETCs.
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Affiliation(s)
- Lu Yu
- High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei 230031, China
| | - Zhenzhen Min
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences and Affiliated Hospital, Key Laboratory of Aging and Cancer Biology of Zhejiang Province, Hangzhou Normal University, Hangzhou 311121, China
| | - Menghua Liu
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences and Affiliated Hospital, Key Laboratory of Aging and Cancer Biology of Zhejiang Province, Hangzhou Normal University, Hangzhou 311121, China
| | - Yueyong Xin
- Photosynthesis Research Center, College of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou 311121, China
| | - Aokun Liu
- High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei 230031, China
| | - Jian Kuang
- The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, Center for Bioanalytical Chemistry, Hefei National Laboratory of Physical Science at Microscale, University of Science and Technology of China, Hefei 230026, China
| | - Wenping Wu
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences and Affiliated Hospital, Key Laboratory of Aging and Cancer Biology of Zhejiang Province, Hangzhou Normal University, Hangzhou 311121, China
| | - Jingyi Wu
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences and Affiliated Hospital, Key Laboratory of Aging and Cancer Biology of Zhejiang Province, Hangzhou Normal University, Hangzhou 311121, China
| | - Huimin He
- Photosynthesis Research Center, College of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou 311121, China
| | - Jiyu Xin
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences and Affiliated Hospital, Key Laboratory of Aging and Cancer Biology of Zhejiang Province, Hangzhou Normal University, Hangzhou 311121, China
| | - Robert E Blankenship
- Departments of Biology and Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Changlin Tian
- High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei 230031, China; The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, Center for Bioanalytical Chemistry, Hefei National Laboratory of Physical Science at Microscale, University of Science and Technology of China, Hefei 230026, China
| | - Xiaoling Xu
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences and Affiliated Hospital, Key Laboratory of Aging and Cancer Biology of Zhejiang Province, Hangzhou Normal University, Hangzhou 311121, China; Photosynthesis Research Center, College of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou 311121, China.
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6
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Liu LN, Bracun L, Li M. Structural diversity and modularity of photosynthetic RC-LH1 complexes. Trends Microbiol 2024; 32:38-52. [PMID: 37380557 DOI: 10.1016/j.tim.2023.06.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2023] [Revised: 06/03/2023] [Accepted: 06/05/2023] [Indexed: 06/30/2023]
Abstract
Bacterial photosynthesis is essential for sustaining life on Earth as it aids in carbon assimilation, atmospheric composition, and ecosystem maintenance. Many bacteria utilize anoxygenic photosynthesis to convert sunlight into chemical energy while producing organic matter. The core machinery of anoxygenic photosynthesis performed by purple photosynthetic bacteria and Chloroflexales is the reaction center-light-harvesting 1 (RC-LH1) pigment-protein supercomplex. In this review, we discuss recent structural studies of RC-LH1 core complexes based on the advancement in structural biology techniques. These studies have provided fundamental insights into the assembly mechanisms, structural variations, and modularity of RC-LH1 complexes across different bacterial species, highlighting their functional adaptability. Understanding the natural architectures of RC-LH1 complexes will facilitate the design and engineering of artificial photosynthetic systems, which can enhance photosynthetic efficiency and potentially find applications in sustainable energy production and carbon capture.
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Affiliation(s)
- Lu-Ning Liu
- Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool L69 7ZB, UK; College of Marine Life Sciences and Frontiers Science Center for Deep Ocean Multispheres and Earth System, Ocean University of China, Qingdao 266003, China.
| | - Laura Bracun
- Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool L69 7ZB, UK
| | - Mei Li
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
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7
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Hao JF, Yamano N, Qi CH, Zhang Y, Ma F, Wang P, Yu LJ, Zhang JP. Carotenoid-Mediated Long-Range Energy Transfer in the Light Harvesting-Reaction Center Complex from Photosynthetic Bacterium Roseiflexus castenholzii. J Phys Chem B 2023; 127:10360-10369. [PMID: 37983555 DOI: 10.1021/acs.jpcb.3c07087] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2023]
Abstract
The light harvesting-reaction center complex (LH-RC) of Roseiflexus castenholzii binds bacteriochlorophylls a (BChls a), B800 and B880, absorbing around 800 and 880 nm, respectively. We comparatively investigated the interband excitation energy transfer (EET) dynamics of the wild-type LH-RC (wt-LH-RC) of Rfl. castenholzii and its carotenoid (Car)-less mutant (m-LH-RC) and found that Car can boost the B800 → B880 EET rate from (2.43 ps)-1 to (1.75 ps)-1, accounting for 38% acceleration of the EET process. Interestingly, photoexcitation of wt-LH-RC at 800 nm induced pronounced excitation dynamics of Car despite the insufficient photon energy for direct Car excitation, a phenomenon which is attributed to the BChl-Car exciplex 1[B800(↑↑)···Car(↓↓)]*. Such an exciplex is suggested to play an essential role in promoting the B800 → B880 EET process, as corroborated by the recently reported cryo-EM structures of wt-LH-RC and m-LH-RC. The mechanism of Car-mediated EET will be helpful to deepen the understanding of the role of Car in bacterial photosynthesis.
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Affiliation(s)
- Jin-Fang Hao
- Key Laboratory of Advanced Light Conversion Materials and Biophotonics, Department of Chemistry, Renmin University of China, Beijing 100872, P. R. China
| | - Nami Yamano
- Key Laboratory of Advanced Light Conversion Materials and Biophotonics, Department of Chemistry, Renmin University of China, Beijing 100872, P. R. China
| | - Chen-Hui Qi
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, P. R. China
| | - Yan Zhang
- Key Laboratory of Advanced Light Conversion Materials and Biophotonics, Department of Chemistry, Renmin University of China, Beijing 100872, P. R. China
| | - Fei Ma
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, P. R. China
| | - Peng Wang
- Key Laboratory of Advanced Light Conversion Materials and Biophotonics, Department of Chemistry, Renmin University of China, Beijing 100872, P. R. China
| | - Long-Jiang Yu
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, P. R. China
| | - Jian-Ping Zhang
- Key Laboratory of Advanced Light Conversion Materials and Biophotonics, Department of Chemistry, Renmin University of China, Beijing 100872, P. R. China
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8
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Xin J, Shi Y, Zhang X, Yuan X, Xin Y, He H, Shen J, Blankenship RE, Xu X. Carotenoid assembly regulates quinone diffusion and the Roseiflexus castenholzii reaction center-light harvesting complex architecture. eLife 2023; 12:e88951. [PMID: 37737710 PMCID: PMC10516601 DOI: 10.7554/elife.88951] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Accepted: 08/16/2023] [Indexed: 09/23/2023] Open
Abstract
Carotenoid (Car) pigments perform central roles in photosynthesis-related light harvesting (LH), photoprotection, and assembly of functional pigment-protein complexes. However, the relationships between Car depletion in the LH, assembly of the prokaryotic reaction center (RC)-LH complex, and quinone exchange are not fully understood. Here, we analyzed native RC-LH (nRC-LH) and Car-depleted RC-LH (dRC-LH) complexes in Roseiflexus castenholzii, a chlorosome-less filamentous anoxygenic phototroph that forms the deepest branch of photosynthetic bacteria. Newly identified exterior Cars functioned with the bacteriochlorophyll B800 to block the proposed quinone channel between LHαβ subunits in the nRC-LH, forming a sealed LH ring that was disrupted by transmembrane helices from cytochrome c and subunit X to allow quinone shuttling. dRC-LH lacked subunit X, leading to an exposed LH ring with a larger opening, which together accelerated the quinone exchange rate. We also assigned amino acid sequences of subunit X and two hypothetical proteins Y and Z that functioned in forming the quinone channel and stabilizing the RC-LH interactions. This study reveals the structural basis by which Cars assembly regulates the architecture and quinone exchange of bacterial RC-LH complexes. These findings mark an important step forward in understanding the evolution and diversity of prokaryotic photosynthetic apparatus.
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Affiliation(s)
- Jiyu Xin
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences and The Affiliated Hospital of Hangzhou Normal UniversityHangzhouChina
| | - Yang Shi
- Liangzhu Laboratory, MOE Frontier Science Center for Brain Science and Brain-machine Integration, State Key Laboratory of Brain-machine Intelligence & Department of Neurobiology and Department of Pathology of the First Affiliated Hospital, Zhejiang University School of Medicine, Zhejiang UniversityHangzhouChina
| | - Xin Zhang
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences and The Affiliated Hospital of Hangzhou Normal UniversityHangzhouChina
- Photosynthesis Research Center, College of Life and Environmental Sciences, Hangzhou Normal UniversityHangzhouChina
| | - Xinyi Yuan
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences and The Affiliated Hospital of Hangzhou Normal UniversityHangzhouChina
- Photosynthesis Research Center, College of Life and Environmental Sciences, Hangzhou Normal UniversityHangzhouChina
| | - Yueyong Xin
- Photosynthesis Research Center, College of Life and Environmental Sciences, Hangzhou Normal UniversityHangzhouChina
| | - Huimin He
- Photosynthesis Research Center, College of Life and Environmental Sciences, Hangzhou Normal UniversityHangzhouChina
| | - Jiejie Shen
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences and The Affiliated Hospital of Hangzhou Normal UniversityHangzhouChina
| | - Robert E Blankenship
- Departments of Biology and Chemistry, Washington University in St. LouisSt. LouisUnited States
| | - Xiaoling Xu
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences and The Affiliated Hospital of Hangzhou Normal UniversityHangzhouChina
- Photosynthesis Research Center, College of Life and Environmental Sciences, Hangzhou Normal UniversityHangzhouChina
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9
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Qi CH, Wang GL, Wang FF, Xin Y, Zou MJ, Madigan MT, Wang-Otomo ZY, Ma F, Yu LJ. New insights on the photocomplex of Roseiflexus castenholzii revealed from comparisons of native and carotenoid-depleted complexes. J Biol Chem 2023; 299:105057. [PMID: 37468106 PMCID: PMC10432797 DOI: 10.1016/j.jbc.2023.105057] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2023] [Revised: 07/08/2023] [Accepted: 07/12/2023] [Indexed: 07/21/2023] Open
Abstract
In wild-type phototrophic organisms, carotenoids (Crts) are primarily packed into specific pigment-protein complexes along with (Bacterio)chlorophylls and play important roles in the photosynthesis. Diphenylamine (DPA) inhibits carotenogenesis but not phototrophic growth of anoxygenic phototrophs and eliminates virtually all Crts from photocomplexes. To investigate the effect of Crts on assembly of the reaction center-light-harvesting (RC-LH) complex from the filamentous anoxygenic phototroph Roseiflexus (Rfl.) castenholzii, we generated carotenoidless (Crt-less) RC-LH complexes by growing cells in the presence of DPA. Here, we present cryo-EM structures of the Rfl. castenholzii native and Crt-less RC-LH complexes with resolutions of 2.86 Å and 2.85 Å, respectively. From the high-quality map obtained, several important but previously unresolved details in the Rfl. castenholzii RC-LH structure were determined unambiguously including the assignment and likely function of three small polypeptides, and the content and spatial arrangement of Crts with bacteriochlorophyll molecules. The overall structures of Crt-containing and Crt-less complexes are similar. However, structural comparisons showed that only five Crts remain in complexes from DPA-treated cells and that the subunit X (TMx) flanked on the N-terminal helix of the Cyt-subunit is missing. Based on these results, the function of Crts in the assembly of the Rfl. castenholzii RC-LH complex and the molecular mechanism of quinone exchange is discussed. These structural details provide a fresh look at the photosynthetic apparatus of an evolutionary ancient phototroph as well as new insights into the importance of Crts for proper assembly and functioning of the RC-LH complex.
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Affiliation(s)
- Chen-Hui Qi
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing, China; University of Chinese Academy of Sciences, Beijing, China
| | - Guang-Lei Wang
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing, China; University of Chinese Academy of Sciences, Beijing, China
| | - Fang-Fang Wang
- National Facility for Protein Science in Shanghai, Zhangjiang Lab, Shanghai Advanced Research Institute, Chinese Academy of Science, Shanghai, China
| | - Yueyong Xin
- College of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou, China
| | - Mei-Juan Zou
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing, China
| | - Michael T Madigan
- Department of Microbiology, School of Biological Sciences, Southern Illinois University, Carbondale, Illinois, USA
| | | | - Fei Ma
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing, China.
| | - Long-Jiang Yu
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing, China.
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10
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Zabelin AA, Khristin AM, Kovalev VB, Khatypov RA, Shkuropatov AY. Primary charge separation in native and plant pheophytin a-modified reaction centers of Chloroflexus aurantiacus: Ultrafast transient absorption measurements at low temperature. BIOCHIMICA ET BIOPHYSICA ACTA. BIOENERGETICS 2023; 1864:148976. [PMID: 37061174 DOI: 10.1016/j.bbabio.2023.148976] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Revised: 03/31/2023] [Accepted: 04/06/2023] [Indexed: 04/17/2023]
Abstract
Ultrafast transient absorption (TA) spectroscopy was used to study electron transfer (ET) at 100 K in native (as isolated) reaction centers (RCs) of the green filamentous photosynthetic bacterium Chloroflexus (Cfl.) aurantiacus. The rise and decay of the 1028 nm anion absorption band of the monomeric bacteriochlorophyll a molecule at the BA binding site were monitored as indicators of the formation and decay of the P+BA- state, respectively (P is the primary electron donor, a dimer of bacteriochlorophyll a molecules). Global analysis of the TA data indicated the presence of at least two populations of the P⁎ excited state, which decay by distinct means, forming the state P+HA- (HA is a photochemically active bacteriopheophytin a molecule). In one population (~65 %), P⁎ decays in ~2 ps with the formation of P+HA- via a short-lived P+BA- intermediate in a two-step ET process P⁎ → P+BA- → P+HA-. In another population (~35 %), P⁎ decays in ~20 ps to form P+HA- via a superexchange mechanism without producing measurable amounts of P+BA-. Similar TA measurements performed on chemically modified RCs of Cfl. aurantiacus containing plant pheophytin a at the HA binding site also showed the presence of two P⁎ populations (~2 and ~20 ps), with P⁎ decaying through P+BA- only in the ~2 ps population. At 100 K, the quantum yield of primary charge separation in native RCs is determined to be close to unity. The results are discussed in terms of involving a one-step P⁎ → P+HA- superexchange process as an alternative highly efficient ET pathway in Cfl. aurantiacus RCs.
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Affiliation(s)
- Alexey A Zabelin
- Institute of Basic Biological Problems of the Russian Academy of Sciences, Federal Research Center "Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences", 142290 Pushchino, Moscow Region, Russian Federation
| | - Anton M Khristin
- Institute of Basic Biological Problems of the Russian Academy of Sciences, Federal Research Center "Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences", 142290 Pushchino, Moscow Region, Russian Federation
| | - Vyacheslav B Kovalev
- Institute of Basic Biological Problems of the Russian Academy of Sciences, Federal Research Center "Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences", 142290 Pushchino, Moscow Region, Russian Federation
| | - Ravil A Khatypov
- Institute of Basic Biological Problems of the Russian Academy of Sciences, Federal Research Center "Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences", 142290 Pushchino, Moscow Region, Russian Federation
| | - Anatoly Yu Shkuropatov
- Institute of Basic Biological Problems of the Russian Academy of Sciences, Federal Research Center "Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences", 142290 Pushchino, Moscow Region, Russian Federation.
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11
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Gardiner AT, Mujakić I, Bína D, Gardian Z, Kopejtka K, Nupur, Qian P, Koblížek M. Characterisation of the photosynthetic complexes from the marine gammaproteobacterium Congregibacter litoralis KT71. BIOCHIMICA ET BIOPHYSICA ACTA. BIOENERGETICS 2023; 1864:148946. [PMID: 36455648 DOI: 10.1016/j.bbabio.2022.148946] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2022] [Revised: 11/02/2022] [Accepted: 11/22/2022] [Indexed: 11/29/2022]
Abstract
Possibly the most abundant group of anoxygenic phototrophs are marine photoheterotrophic Gammaproteobacteria belonging to the NOR5/OM60 clade. As little is known about their photosynthetic apparatus, the photosynthetic complexes from the marine phototrophic bacterium Congregibacter litoralis KT71 were purified and spectroscopically characterised. The intra-cytoplasmic membranes contain a smaller amount of photosynthetic complexes when compared with anaerobic purple bacteria. Moreover, the intra-cytoplasmic membranes contain only a minimum amount of peripheral LH2 complexes. The complexes are populated by bacteriochlorophyll a, spirilloxanthin and two novel ketocarotenoids, with biophysical and biochemical properties similar to previously characterised complexes from purple bacteria. The organization of the RC-LH1 complex has been further characterised using cryo-electron microscopy. The overall organisation is similar to the complex from the gammaproteobacterium Thermochromatium tepidum, with the type-II reaction centre surrounded by a slightly elliptical LH1 antenna ring composed of 16 αβ-subunits with no discernible gap or pore. The RC-LH1 and LH2 apoproteins are phylogenetically related to other halophilic species but LH2 also to some alphaproteobacterial species. It seems that the reduction of light-harvesting apparatus and acquisition of novel ketocarotenoids in Congregibacter litoralis KT71 represent specific adaptations for operating the anoxygenic photosynthesis under aerobic conditions at sea.
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Affiliation(s)
- Alastair T Gardiner
- Institute of Microbiology of the Czech Academy of Sciences, 379 81 Třeboň, Czech Republic
| | - Izabela Mujakić
- Institute of Microbiology of the Czech Academy of Sciences, 379 81 Třeboň, Czech Republic; Faculty of Science, University of South Bohemia, 370 05 České Budějovice, Czech Republic
| | - David Bína
- Faculty of Science, University of South Bohemia, 370 05 České Budějovice, Czech Republic; Biology Centre, Czech Academy of Sciences, Institute of Plant Molecular Biology, Branišovská 1760, 370 05 České Budějovice, Czech Republic
| | - Zdenko Gardian
- Faculty of Science, University of South Bohemia, 370 05 České Budějovice, Czech Republic; Biology Centre, Czech Academy of Sciences, Institute of Parasitology, Branišovská 1760, 370 05 České Budějovice, Czech Republic
| | - Karel Kopejtka
- Institute of Microbiology of the Czech Academy of Sciences, 379 81 Třeboň, Czech Republic
| | - Nupur
- Institute of Microbiology of the Czech Academy of Sciences, 379 81 Třeboň, Czech Republic
| | - Pu Qian
- Materials and Structure Analysis, Thermofisher Scientific, Achtseweg Noord 5, 5651 GG Eindhoven, Netherlands
| | - Michal Koblížek
- Institute of Microbiology of the Czech Academy of Sciences, 379 81 Třeboň, Czech Republic; Faculty of Science, University of South Bohemia, 370 05 České Budějovice, Czech Republic.
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12
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Bracun L, Yamagata A, Christianson BM, Shirouzu M, Liu LN. Cryo-EM structure of a monomeric RC-LH1-PufX supercomplex with high-carotenoid content from Rhodobacter capsulatus. Structure 2023; 31:318-328.e3. [PMID: 36738736 DOI: 10.1016/j.str.2023.01.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Revised: 12/30/2022] [Accepted: 01/11/2023] [Indexed: 02/05/2023]
Abstract
In purple photosynthetic bacteria, the photochemical reaction center (RC) and light-harvesting complex 1 (LH1) assemble to form monomeric or dimeric RC-LH1 membrane complexes, essential for bacterial photosynthesis. Here, we report a 2.59-Å resolution cryoelectron microscopy (cryo-EM) structure of the RC-LH1 supercomplex from Rhodobacter capsulatus. We show that Rba. capsulatus RC-LH1 complexes are exclusively monomers in which the RC is surrounded by a 15-subunit LH1 ring. Incorporation of a transmembrane polypeptide PufX leads to a large opening within the LH1 ring. Each LH1 subunit associates two carotenoids and two bacteriochlorophylls, which is similar to Rba. sphaeroides RC-LH1 but more than one carotenoid per LH1 in Rba. veldkampii RC-LH1 monomer. Collectively, the unique Rba. capsulatus RC-LH1-PufX represents an intermediate structure between Rba. sphaeroides and Rba. veldkampii RC-LH1-PufX. Comparison of PufX from the three Rhodobacter species indicates the important residues involved in dimerization of RC-LH1.
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Affiliation(s)
- Laura Bracun
- Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool L69 7ZB, UK; Laboratory for Protein Functional and Structural Biology, RIKEN Center for Biosystems Dynamics Research, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan
| | - Atsushi Yamagata
- Laboratory for Protein Functional and Structural Biology, RIKEN Center for Biosystems Dynamics Research, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan
| | - Bern M Christianson
- Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool L69 7ZB, UK
| | - Mikako Shirouzu
- Laboratory for Protein Functional and Structural Biology, RIKEN Center for Biosystems Dynamics Research, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan
| | - Lu-Ning Liu
- Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool L69 7ZB, UK; College of Marine Life Sciences and Frontiers Science Center for Deep Ocean Multispheres and Earth System, Ocean University of China, Qingdao 266003, China.
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13
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Kimura Y, Tani K, Madigan MT, Wang-Otomo ZY. Advances in the Spectroscopic and Structural Characterization of Core Light-Harvesting Complexes from Purple Phototrophic Bacteria. J Phys Chem B 2023; 127:6-17. [PMID: 36594654 DOI: 10.1021/acs.jpcb.2c06638] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Purple phototrophic bacteria are ancient anoxygenic phototrophs and attractive research tools because they capture light energy in the near-infrared (NIR) region of the spectrum and transform it into chemical energy by way of uphill energy transfers. The heart of this reaction occurs in light-harvesting 1-reaction center (LH1-RC) complexes, which are the simplest model systems for understanding basic photosynthetic reactions within type-II (quinone-utilizing) reaction centers. In this Perspective, we highlight structure-function relationships concerning unresolved fundamental processes in purple bacterial photosynthesis, including the diversified light-harvesting capacity of LH1-associated BChl molecules, energies necessary for photoelectric conversion in the RC special pairs, and quinone transport mechanisms. Based on recent progress in the spectroscopic and structural analysis of LH1-RC complexes from a variety of purple phototrophs, we discuss several key factors for understanding how purple bacteria resource light energy in the inherently energy-poor NIR region of the electromagnetic spectrum.
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Affiliation(s)
- Yukihiro Kimura
- Department of Agrobioscience, Graduate School of Agriculture, Kobe University, Nada, Kobe 657-8501, Japan
| | - Kazutoshi Tani
- Graduate School of Medicine, Mie University, Tsu 514-8507, Japan
| | - Michael T Madigan
- Department of Microbiology, School of Biological Sciences, Southern Illinois University, Carbondale, Illinois 62901, United States
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14
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Structure of the Acidobacteria homodimeric reaction center bound with cytochrome c. Nat Commun 2022; 13:7745. [PMID: 36517472 PMCID: PMC9751088 DOI: 10.1038/s41467-022-35460-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2022] [Accepted: 12/02/2022] [Indexed: 12/23/2022] Open
Abstract
Photosynthesis converts light energy to chemical energy to fuel life on earth. Light energy is harvested by antenna pigments and transferred to reaction centers (RCs) to drive the electron transfer (ET) reactions. Here, we present cryo-electron microscopy (cryo-EM) structures of two forms of the RC from the microaerophilic Chloracidobacterium thermophilum (CabRC): one containing 10 subunits, including two different cytochromes; and the other possessing two additional subunits, PscB and PscZ. The larger form contained 2 Zn-bacteriochlorophylls, 16 bacteriochlorophylls, 10 chlorophylls, 2 lycopenes, 2 hemes, 3 Fe4S4 clusters, 12 lipids, 2 Ca2+ ions and 6 water molecules, revealing a type I RC with an ET chain involving two hemes and a hybrid antenna containing bacteriochlorophylls and chlorophylls. Our results provide a structural basis for understanding the excitation energy and ET within the CabRC and offer evolutionary insights into the origin and adaptation of photosynthetic RCs.
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15
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Tani K, Kanno R, Kurosawa K, Takaichi S, Nagashima KVP, Hall M, Yu LJ, Kimura Y, Madigan MT, Mizoguchi A, Humbel BM, Wang-Otomo ZY. An LH1–RC photocomplex from an extremophilic phototroph provides insight into origins of two photosynthesis proteins. Commun Biol 2022; 5:1197. [DOI: 10.1038/s42003-022-04174-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Accepted: 10/26/2022] [Indexed: 11/09/2022] Open
Abstract
AbstractRhodopila globiformis is the most acidophilic of anaerobic purple phototrophs, growing optimally in culture at pH 5. Here we present a cryo-EM structure of the light-harvesting 1–reaction center (LH1–RC) complex from Rhodopila globiformis at 2.24 Å resolution. All purple bacterial cytochrome (Cyt, encoded by the gene pufC) subunit-associated RCs with known structures have their N-termini truncated. By contrast, the Rhodopila globiformis RC contains a full-length tetra-heme Cyt with its N-terminus embedded in the membrane forming an α-helix as the membrane anchor. Comparison of the N-terminal regions of the Cyt with PufX polypeptides widely distributed in Rhodobacter species reveals significant structural similarities, supporting a longstanding hypothesis that PufX is phylogenetically related to the N-terminus of the RC-bound Cyt subunit and that a common ancestor of phototrophic Proteobacteria contained a full-length tetra-heme Cyt subunit that evolved independently through partial deletions of its pufC gene. Eleven copies of a novel γ-like polypeptide were also identified in the bacteriochlorophyll a-containing Rhodopila globiformis LH1 complex; γ-polypeptides have previously been found only in the LH1 of bacteriochlorophyll b-containing species. These features are discussed in relation to their predicted functions of stabilizing the LH1 structure and regulating quinone transport under the warm acidic conditions.
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16
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Proteomic Time-Course Analysis of the Filamentous Anoxygenic Phototrophic Bacterium, Chloroflexus aurantiacus, during the Transition from Respiration to Phototrophy. Microorganisms 2022; 10:microorganisms10071288. [PMID: 35889008 PMCID: PMC9316378 DOI: 10.3390/microorganisms10071288] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Revised: 06/21/2022] [Accepted: 06/22/2022] [Indexed: 02/05/2023] Open
Abstract
Chloroflexus aurantiacus is a filamentous anoxygenic phototrophic bacterium that grows chemotrophically under oxic conditions and phototrophically under anoxic conditions. Because photosynthesis-related genes are scattered without any gene clusters in the genome, it is still unclear how this bacterium regulates protein expression in response to environmental changes. In this study, we performed a proteomic time-course analysis of how C. aurantiacus expresses proteins to acclimate to environmental changes, namely the transition from chemoheterotrophic respiratory to photoheterotrophic growth mode. Proteomic analysis detected a total of 2520 proteins out of 3934 coding sequences in the C. aurantiacus genome from samples collected at 13 time points. Almost all proteins for reaction centers, light-harvesting chlorosomes, and carbon fixation pathways were successfully detected during the growing phases in which optical densities and relative bacteriochlorophyll c contents increased simultaneously. Combination of proteomics and pigment analysis suggests that the self-aggregation of bacteriochlorophyllide c could precede the esterification of the hydrophobic farnesyl tail in cells. Cytoplasmic subunits of alternative complex III were interchanged between oxic and anoxic conditions, although membrane-bound subunits were used for both conditions. These data highlight the protein expression dynamics of phototrophy-related genes during the transition from respiration to phototrophy.
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17
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Du J, Xin J, Liu M, Zhang X, He H, Wu J, Xu X. Preparation of Photo-Bioelectrochemical Cells With the RC-LH Complex From Roseiflexus castenholzii. Front Microbiol 2022; 13:928046. [PMID: 35783423 PMCID: PMC9243436 DOI: 10.3389/fmicb.2022.928046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Accepted: 05/30/2022] [Indexed: 11/13/2022] Open
Abstract
Roseiflexus castenholzii is an ancient green non-sulfur bacteria that absorbs the solar energy through bacteriochlorophylls (BChls) bound in the only light harvesting (LH) complex, and transfers to the reaction center (RC), wherein primary charge separation occurs and transforms the energy into electrochemical potentials. In contrast to purple bacteria, R. castenholzii RC-LH (rcRC-LH) does not contain an H subunit. Instead, a tightly bound tetraheme cytochrome c subunit is exposed on the P-side of the RC, which contains three BChls, three bacteriopheophytins (BPheos), two menaquinones, and one iron for electron transfer. These novel structural features of the rcRC-LH are advantageous for enhancing the electron transfer efficiency and subsequent photo-oxidation of the c-type hemes. However, the photochemical properties of rcRC-LH and its applications in developing the photo-bioelectrochemical cells (PBECs) have not been characterized. Here, we prepared a PBEC using overlapped fluorine-doped tin oxide (FTO) glass and Pt-coated glass as electrodes, and rcRC-LH mixed with varying mediators as the electrolyte. Absence of the H subunit allows rcRC-LH to be selectively adhered onto the hydrophilic surface of the front electrode with its Q-side. Upon illumination, the photogenerated electrons directly enter the front electrode and transfer to the counter electrode, wherein the accepted electrons pass through the exposed c-type hemes to reduce the excited P+, generating a steady-state current of up to 320 nA/cm2 when using 1-Methoxy-5-methylphenazinium methyl sulfate (PMS) as mediator. This study demonstrated the novel photoelectric properties of rcRC-LH and its advantages in preparing effective PBECs, showcasing a potential of this complex in developing new type PBECs.
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Affiliation(s)
- Jinsong Du
- Photosynthesis Research Center, Hangzhou Normal University, Hangzhou, China
| | - Jiyu Xin
- Photosynthesis Research Center, Hangzhou Normal University, Hangzhou, China
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, The Affiliated Hospital of Hangzhou Normal University, Hangzhou, China
| | - Menghua Liu
- Photosynthesis Research Center, Hangzhou Normal University, Hangzhou, China
| | - Xin Zhang
- Photosynthesis Research Center, Hangzhou Normal University, Hangzhou, China
| | - Huimin He
- Photosynthesis Research Center, Hangzhou Normal University, Hangzhou, China
| | - Jingyi Wu
- Photosynthesis Research Center, Hangzhou Normal University, Hangzhou, China
| | - Xiaoling Xu
- Photosynthesis Research Center, Hangzhou Normal University, Hangzhou, China
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, The Affiliated Hospital of Hangzhou Normal University, Hangzhou, China
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18
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Structural basis for the assembly and quinone transport mechanisms of the dimeric photosynthetic RC-LH1 supercomplex. Nat Commun 2022; 13:1977. [PMID: 35418573 PMCID: PMC9007983 DOI: 10.1038/s41467-022-29563-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Accepted: 03/22/2022] [Indexed: 12/15/2022] Open
Abstract
The reaction center (RC) and light-harvesting complex 1 (LH1) form a RC-LH1 core supercomplex that is vital for the primary reactions of photosynthesis in purple phototrophic bacteria. Some species possess the dimeric RC-LH1 complex with a transmembrane polypeptide PufX, representing the largest photosynthetic complex in anoxygenic phototrophs. However, the details of the architecture and assembly mechanism of the RC-LH1 dimer are unclear. Here we report seven cryo-electron microscopy (cryo-EM) structures of RC-LH1 supercomplexes from Rhodobacter sphaeroides. Our structures reveal that two PufX polypeptides are positioned in the center of the S-shaped RC-LH1 dimer, interlocking association between the components and mediating RC-LH1 dimerization. Moreover, we identify another transmembrane peptide, designated PufY, which is located between the RC and LH1 subunits near the LH1 opening. PufY binds a quinone molecule and prevents LH1 subunits from completely encircling the RC, creating a channel for quinone/quinol exchange. Genetic mutagenesis, cryo-EM structures, and computational simulations provide a mechanistic understanding of the assembly and electron transport pathways of the RC-LH1 dimer and elucidate the roles of individual components in ensuring the structural and functional integrity of the photosynthetic supercomplex.
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19
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Kimura Y, Imanishi M, Li Y, Yura Y, Ohno T, Saga Y, Madigan MT, Wang-Otomo ZY. Identification of metal-sensitive structural changes in the Ca 2+-binding photocomplex from Thermochromatium tepidum by isotope-edited vibrational spectroscopy. J Chem Phys 2022; 156:105101. [DOI: 10.1063/5.0075600] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Calcium ions play a dual role in expanding the spectral diversity and structural stability of photocomplexes from several Ca2+-requiring purple sulfur phototrophic bacteria. Here, metal-sensitive structural changes in the isotopically labeled light-harvesting 1 reaction center (LH1-RC) complexes from the thermophilic purple sulfur bacterium Thermochromatium ( Tch.) tepidum were investigated by perfusion-induced attenuated total reflection (ATR) Fourier transform infrared (FTIR) spectroscopy. The ATR-FTIR difference spectra induced by exchanges between native Ca2+ and exogenous Ba2+ exhibited interconvertible structural and/or conformational changes in the metal binding sites at the LH1 C-terminal region. Most of the characteristic Ba2+/Ca2+ difference bands were detected even when only Ca ions were removed from the LH1-RC complexes, strongly indicating the pivotal roles of Ca2+ in maintaining the LH1-RC structure of Tch. tepidum. Upon 15N-, 13C- or 2H-labeling, the LH1-RC complexes exhibited characteristic 15N/14N-, 13C/12C-, or 2H/1H-isotopic shifts for the Ba2+/Ca2+ difference bands. Some of the 15N/14N or 13C/12C bands were also sensitive to further 2H-labelings. Given the band frequencies and their isotopic shifts along with the structural information of the Tch. tepidum LH1-RC complexes, metal-sensitive FTIR bands were tentatively identified to the vibrational modes of the polypeptide main chains and side chains comprising the metal binding sites. Furthermore, important new IR marker bands highly sensitive to the LH1 BChl a conformation in the Ca2+-bound states were revealed based on both ATR-FTIR and near-infrared Raman analyses. The present approach provides valuable insights concerning the dynamic equilibrium between the Ca2+- and Ba2+-bound states statically resolved by x-ray crystallography.
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Affiliation(s)
- Yukihiro Kimura
- Graduate School of Agricultural Science, Kobe University, Kobe 657-8501, Japan
| | - Michie Imanishi
- Graduate School of Agricultural Science, Kobe University, Kobe 657-8501, Japan
| | - Yong Li
- Graduate School of Agricultural Science, Kobe University, Kobe 657-8501, Japan
| | - Yuki Yura
- Graduate School of Agricultural Science, Kobe University, Kobe 657-8501, Japan
| | - Takashi Ohno
- Graduate School of Agricultural Science, Kobe University, Kobe 657-8501, Japan
| | - Yoshitaka Saga
- Department of Chemistry, Faculty of Science and Engineering, Kindai University, Higashi-Osaka 577-8502, Japan
| | - Michael T. Madigan
- School of Biological Sciences, Department of Microbiology, Southern Illinois University, Carbondale, Illinois 62901, USA
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20
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Qian P, Gardiner AT, Šímová I, Naydenova K, Croll TI, Jackson PJ, Nupur, Kloz M, Čubáková P, Kuzma M, Zeng Y, Castro-Hartmann P, van Knippenberg B, Goldie KN, Kaftan D, Hrouzek P, Hájek J, Agirre J, Siebert CA, Bína D, Sader K, Stahlberg H, Sobotka R, Russo CJ, Polívka T, Hunter CN, Koblížek M. 2.4-Å structure of the double-ring Gemmatimonas phototrophica photosystem. SCIENCE ADVANCES 2022; 8:eabk3139. [PMID: 35171663 PMCID: PMC8849296 DOI: 10.1126/sciadv.abk3139] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Accepted: 12/22/2021] [Indexed: 07/21/2023]
Abstract
Phototrophic Gemmatimonadetes evolved the ability to use solar energy following horizontal transfer of photosynthesis-related genes from an ancient phototrophic proteobacterium. The electron cryo-microscopy structure of the Gemmatimonas phototrophica photosystem at 2.4 Å reveals a unique, double-ring complex. Two unique membrane-extrinsic polypeptides, RC-S and RC-U, hold the central type 2 reaction center (RC) within an inner 16-subunit light-harvesting 1 (LH1) ring, which is encircled by an outer 24-subunit antenna ring (LHh) that adds light-gathering capacity. Femtosecond kinetics reveal the flow of energy within the RC-dLH complex, from the outer LHh ring to LH1 and then to the RC. This structural and functional study shows that G. phototrophica has independently evolved its own compact, robust, and highly effective architecture for harvesting and trapping solar energy.
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Affiliation(s)
- Pu Qian
- Materials and Structural Analysis, Thermo Fisher Scientific, Achtseweg Noord 5, 5651 GG Eindhoven, Netherlands
- School of Biosciences, University of Sheffield, Sheffield S10 2TN, UK
| | - Alastair T. Gardiner
- Center Algatech, Institute of Microbiology, Czech Academy of Sciences, 37981 Třeboň, Czechia
| | - Ivana Šímová
- Faculty of Science, University of South Bohemia, 37005 České Budějovice, Czechia
| | - Katerina Naydenova
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Tristan I. Croll
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge CB2 0XY, UK
| | - Philip J. Jackson
- School of Biosciences, University of Sheffield, Sheffield S10 2TN, UK
| | - Nupur
- Center Algatech, Institute of Microbiology, Czech Academy of Sciences, 37981 Třeboň, Czechia
| | - Miroslav Kloz
- ELI Beamlines, Institute of Physics of the Czech Academy of Sciences, Na Slovance 1999/2, 182 21 Prague, Czechia
| | - Petra Čubáková
- ELI Beamlines, Institute of Physics of the Czech Academy of Sciences, Na Slovance 1999/2, 182 21 Prague, Czechia
| | - Marek Kuzma
- Lab of Molecular Structure, Institute of Microbiology, Czech Academy of Sciences, Prague, Czechia
| | - Yonghui Zeng
- Department of Plant and Environmental Sciences, University of Copenhagen, Nørregade 10, DK-1165 Copenhagen, Denmark
| | - Pablo Castro-Hartmann
- Materials and Structural Analysis, Thermo Fisher Scientific, Achtseweg Noord 5, 5651 GG Eindhoven, Netherlands
| | - Bart van Knippenberg
- Materials and Structural Analysis, Thermo Fisher Scientific, Achtseweg Noord 5, 5651 GG Eindhoven, Netherlands
| | - Kenneth N. Goldie
- BioEM lab, Biozentrum, University of Basel, Mattenstrasse 26, 4058 Basel, Switzerland
| | - David Kaftan
- Center Algatech, Institute of Microbiology, Czech Academy of Sciences, 37981 Třeboň, Czechia
| | - Pavel Hrouzek
- Center Algatech, Institute of Microbiology, Czech Academy of Sciences, 37981 Třeboň, Czechia
| | - Jan Hájek
- Center Algatech, Institute of Microbiology, Czech Academy of Sciences, 37981 Třeboň, Czechia
| | - Jon Agirre
- Department of Chemistry, University of York, York YO10 5DD, UK
| | | | - David Bína
- Faculty of Science, University of South Bohemia, 37005 České Budějovice, Czechia
| | - Kasim Sader
- Materials and Structural Analysis, Thermo Fisher Scientific, Achtseweg Noord 5, 5651 GG Eindhoven, Netherlands
| | - Henning Stahlberg
- Laboratory of Biological Electron Microscopy, Institute of Physics, SB, EPFL, and Faculty of Biology and Medicine, Uni Lausanne, CH-1015 Lausanne, Switzerland
| | - Roman Sobotka
- Center Algatech, Institute of Microbiology, Czech Academy of Sciences, 37981 Třeboň, Czechia
- Faculty of Science, University of South Bohemia, 37005 České Budějovice, Czechia
| | - Christopher J. Russo
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Tomáš Polívka
- Faculty of Science, University of South Bohemia, 37005 České Budějovice, Czechia
| | - C. Neil Hunter
- School of Biosciences, University of Sheffield, Sheffield S10 2TN, UK
| | - Michal Koblížek
- Center Algatech, Institute of Microbiology, Czech Academy of Sciences, 37981 Třeboň, Czechia
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21
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Sutherland GA, Qian P, Hunter CN, Swainsbury DJ, Hitchcock A. Engineering purple bacterial carotenoid biosynthesis to study the roles of carotenoids in light-harvesting complexes. Methods Enzymol 2022; 674:137-184. [DOI: 10.1016/bs.mie.2022.04.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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22
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A previously unrecognized membrane protein in the Rhodobacter sphaeroides LH1-RC photocomplex. Nat Commun 2021; 12:6300. [PMID: 34728609 PMCID: PMC8564508 DOI: 10.1038/s41467-021-26561-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Accepted: 10/01/2021] [Indexed: 11/27/2022] Open
Abstract
Rhodobacter (Rba.) sphaeroides is the most widely used model organism in bacterial photosynthesis. The light-harvesting-reaction center (LH1-RC) core complex of this purple phototroph is characterized by the co-existence of monomeric and dimeric forms, the presence of the protein PufX, and approximately two carotenoids per LH1 αβ-polypeptides. Despite many efforts, structures of the Rba. sphaeroides LH1-RC have not been obtained at high resolutions. Here we report a cryo-EM structure of the monomeric LH1-RC from Rba. sphaeroides strain IL106 at 2.9 Å resolution. The LH1 complex forms a C-shaped structure composed of 14 αβ-polypeptides around the RC with a large ring opening. From the cryo-EM density map, a previously unrecognized integral membrane protein, referred to as protein-U, was identified. Protein-U has a U-shaped conformation near the LH1-ring opening and was annotated as a hypothetical protein in the Rba. sphaeroides genome. Deletion of protein-U resulted in a mutant strain that expressed a much-reduced amount of the dimeric LH1-RC, indicating an important role for protein-U in dimerization of the LH1-RC complex. PufX was located opposite protein-U on the LH1-ring opening, and both its position and conformation differed from that of previous reports of dimeric LH1-RC structures obtained at low-resolution. Twenty-six molecules of the carotenoid spheroidene arranged in two distinct configurations were resolved in the Rba. sphaeroides LH1 and were positioned within the complex to block its channels. Our findings offer an exciting new view of the core photocomplex of Rba. sphaeroides and the connections between structure and function in bacterial photocomplexes in general. Rhodobacter (Rba.) sphaeroides is a model organism for studying bacterial photosynthesis. Here, the authors present the 2.9 Å cryo-EM structure of the monomeric light-harvesting-reaction center core complex from Rba. sphaeroides strain IL106, which revealed the position and conformation of PufX and the presence of an additional component protein-U, an integral membrane protein.
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23
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Cryo-EM structure of the monomeric Rhodobacter sphaeroides RC-LH1 core complex at 2.5 Å. Biochem J 2021; 478:3775-3790. [PMID: 34590677 PMCID: PMC8589327 DOI: 10.1042/bcj20210631] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2021] [Revised: 09/22/2021] [Accepted: 09/30/2021] [Indexed: 12/02/2022]
Abstract
Reaction centre light-harvesting 1 (RC–LH1) complexes are the essential components of bacterial photosynthesis. The membrane-intrinsic LH1 complex absorbs light and the energy migrates to an enclosed RC where a succession of electron and proton transfers conserves the energy as a quinol, which is exported to the cytochrome bc1 complex. In some RC–LH1 variants quinols can diffuse through small pores in a fully circular, 16-subunit LH1 ring, while in others missing LH1 subunits create a gap for quinol export. We used cryogenic electron microscopy to obtain a 2.5 Å resolution structure of one such RC–LH1, a monomeric complex from Rhodobacter sphaeroides. The structure shows that the RC is partly enclosed by a 14-subunit LH1 ring in which each αβ heterodimer binds two bacteriochlorophylls and, unusually for currently reported complexes, two carotenoids rather than one. Although the extra carotenoids confer an advantage in terms of photoprotection and light harvesting, they could impede passage of quinones through small, transient pores in the LH1 ring, necessitating a mechanism to create a dedicated quinone channel. The structure shows that two transmembrane proteins play a part in stabilising an open ring structure; one of these components, the PufX polypeptide, is augmented by a hitherto undescribed protein subunit we designate as protein-Y, which lies against the transmembrane regions of the thirteenth and fourteenth LH1α polypeptides. Protein-Y prevents LH1 subunits 11–14 adjacent to the RC QB site from bending inwards towards the RC and, with PufX preventing complete encirclement of the RC, this pair of polypeptides ensures unhindered quinone diffusion.
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24
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Cryo-EM structure of the Rhodospirillum rubrum RC-LH1 complex at 2.5 Å. Biochem J 2021; 478:3253-3263. [PMID: 34402504 PMCID: PMC8454704 DOI: 10.1042/bcj20210511] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2021] [Revised: 08/12/2021] [Accepted: 08/17/2021] [Indexed: 12/03/2022]
Abstract
The reaction centre light-harvesting 1 (RC–LH1) complex is the core functional component of bacterial photosynthesis. We determined the cryo-electron microscopy (cryo-EM) structure of the RC–LH1 complex from Rhodospirillum rubrum at 2.5 Å resolution, which reveals a unique monomeric bacteriochlorophyll with a phospholipid ligand in the gap between the RC and LH1 complexes. The LH1 complex comprises a circular array of 16 αβ-polypeptide subunits that completely surrounds the RC, with a preferential binding site for a quinone, designated QP, on the inner face of the encircling LH1 complex. Quinols, initially generated at the RC QB site, are proposed to transiently occupy the QP site prior to traversing the LH1 barrier and diffusing to the cytochrome bc1 complex. Thus, the QP site, which is analogous to other such sites in recent cryo-EM structures of RC–LH1 complexes, likely reflects a general mechanism for exporting quinols from the RC–LH1 complex.
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25
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Zabelin AA, Shkuropatov AY. Pigment-modified reaction centers of Chloroflexus aurantiacus: chemical exchange of bacteriopheophytins with plant-type pheophytins. PHOTOSYNTHESIS RESEARCH 2021; 149:313-328. [PMID: 34138452 DOI: 10.1007/s11120-021-00855-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Accepted: 06/06/2021] [Indexed: 06/12/2023]
Abstract
The pigment composition of isolated reaction centers (RCs) of the green filamentous bacterium Chloroflexus (Cfl.) aurantiacus was changed by chemical exchange of native bacteriopheophytin a (BPheo) molecules with externally added pheophytin a (Pheo) or [3-acetyl]-Pheo upon incubation of RC/pheophytin mixtures at room temperature and 45 °C. The modified RCs were characterized by Vis/NIR absorption spectroscopy, and the effect of pigment exchange on RC photochemical activity was assessed by measuring the photoaccumulation of the reduced pigment at the binding site HA. It is shown that both pheophytins can be exchanged into the HA site instead of BPheo by incubation at room temperature. While the newly introduced Pheo molecule is not active in electron transfer, the [3-acetyl]-Pheo molecule is able to replace functionally the photoreducible HA BPheo molecule with the formation of the [3-acetyl]-Pheo- radical anion instead of the BPheo-. After incubation at 45 °C, the majority (~ 90%) of HA BPheo molecules is replaced by both Pheo and [3-acetyl]-Pheo. Only a partial replacement of inactive BPheo molecules with pheophytins is observed even when the incubation temperature is raised to 50 °C. The results are discussed in terms of (i) differences in the accessibility of BPheo binding sites for extraneous pigments depending on structural constraints and incubation temperature and (ii) the effect of the reduction potential of pigments introduced into the HA site on the energetics of the charge separation process. The possible implication of Pheo-exchanged preparations for studying early electron-transfer events in Cfl. aurantiacus RCs is considered.
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Affiliation(s)
- Alexey A Zabelin
- Federal Research Center "Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences", Institute of Basic Biological Problems of the Russian Academy of Sciences, 142290, Pushchino, Moscow Region, Russian Federation
| | - Anatoly Ya Shkuropatov
- Federal Research Center "Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences", Institute of Basic Biological Problems of the Russian Academy of Sciences, 142290, Pushchino, Moscow Region, Russian Federation.
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26
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Kimura Y, Nojima S, Nakata K, Yamashita T, Wang XP, Takenaka S, Akimoto S, Kobayashi M, Madigan MT, Wang-Otomo ZY, Yu LJ. Electrostatic charge controls the lowest LH1 Q y transition energy in the triply extremophilic purple phototrophic bacterium, Halorhodospira halochloris. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2021; 1862:148473. [PMID: 34310933 DOI: 10.1016/j.bbabio.2021.148473] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Revised: 06/18/2021] [Accepted: 07/19/2021] [Indexed: 10/20/2022]
Abstract
Halorhodospira (Hlr.) halochloris is a unique phototrophic purple bacterium because it is a triple extremophile-the organism is thermophilic, alkalophilic, and halophilic. The most striking photosynthetic feature of Hlr. halochloris is that the bacteriochlorophyll (BChl) b-containing core light-harvesting (LH1) complex surrounding its reaction center (RC) exhibits its LH1 Qy absorption maximum at 1016 nm, which is the lowest transition energy among phototrophic organisms. Here we report that this extraordinarily red-shifted LH1 Qy band of Hlr. halochloris exhibits interconvertible spectral shifts depending on the electrostatic charge distribution around the BChl b molecules. The 1016 nm band of the Hlr. halochloris LH1-RC complex was blue-shifted to 958 nm upon desalting or pH decrease but returned to its original position when supplemented with salts or pH increase. Resonance Raman analysis demonstrated that these interconvertible spectral shifts are not associated with the strength of hydrogen-bonding interactions between BChl b and LH1 polypeptides. Furthermore, circular dichroism signals for the LH1 Qy transition of Hlr. halochloris appeared with a positive sign (as in BChl b-containing Blastochloris species) and opposite those of BChl a-containing purple bacteria, possibly due to a combined effect of slight differences in the transition dipole moments between BChl a and BChl b and in the interactions between adjacent BChls in their assembled state. Based on these findings and LH1 amino acid sequences, it is proposed that Hlr. halochloris evolved its unique and tunable light-harvesting system with electrostatic charges in order to carry out photosynthesis and thrive in its punishing hypersaline and alkaline habitat.
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Affiliation(s)
- Yukihiro Kimura
- Department of Agrobioscience, Graduate School of Agriculture, Kobe University, Nada, Kobe 657-8501, Japan.
| | - Shingo Nojima
- Department of Agrobioscience, Graduate School of Agriculture, Kobe University, Nada, Kobe 657-8501, Japan
| | - Kazuna Nakata
- Department of Agrobioscience, Graduate School of Agriculture, Kobe University, Nada, Kobe 657-8501, Japan
| | | | - Xiang-Ping Wang
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | - Shinji Takenaka
- Department of Agrobioscience, Graduate School of Agriculture, Kobe University, Nada, Kobe 657-8501, Japan
| | - Seiji Akimoto
- Department of Science, Graduate School of Science, Kobe University, Nada, Kobe 657-8501, Japan
| | | | - Michael T Madigan
- Department of Microbiology, Southern Illinois University, Carbondale, IL 62901, USA
| | | | - Long-Jiang Yu
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China.
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27
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Bracun L, Yamagata A, Christianson BM, Terada T, Canniffe DP, Shirouzu M, Liu LN. Cryo-EM structure of the photosynthetic RC-LH1-PufX supercomplex at 2.8-Å resolution. SCIENCE ADVANCES 2021; 7:7/25/eabf8864. [PMID: 34134992 PMCID: PMC8208714 DOI: 10.1126/sciadv.abf8864] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Accepted: 05/04/2021] [Indexed: 05/07/2023]
Abstract
The reaction center (RC)-light-harvesting complex 1 (LH1) supercomplex plays a pivotal role in bacterial photosynthesis. Many RC-LH1 complexes integrate an additional protein PufX that is key for bacterial growth and photosynthetic competence. Here, we present a cryo-electron microscopy structure of the RC-LH1-PufX supercomplex from Rhodobacter veldkampii at 2.8-Å resolution. The RC-LH1-PufX monomer contains an LH ring of 15 αβ-polypeptides with a 30-Å gap formed by PufX. PufX acts as a molecular "cross brace" to reinforce the RC-LH1 structure. The unusual PufX-mediated large opening in the LH1 ring and defined arrangement of proteins and cofactors provide the molecular basis for the assembly of a robust RC-LH1-PufX supercomplex and efficient quinone transport and electron transfer. These architectural features represent the natural strategies for anoxygenic photosynthesis and environmental adaptation.
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Affiliation(s)
- Laura Bracun
- Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool L69 7ZB, UK
- Laboratory for Protein Functional and Structural Biology, RIKEN Center for Biosystems Dynamics Research, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan
| | - Atsushi Yamagata
- Laboratory for Protein Functional and Structural Biology, RIKEN Center for Biosystems Dynamics Research, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan
| | - Bern M Christianson
- Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool L69 7ZB, UK
| | - Tohru Terada
- Department of Biotechnology, Graduate School of Agricultural and Life Sciences, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Daniel P Canniffe
- Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool L69 7ZB, UK
| | - Mikako Shirouzu
- Laboratory for Protein Functional and Structural Biology, RIKEN Center for Biosystems Dynamics Research, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan
| | - Lu-Ning Liu
- Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool L69 7ZB, UK.
- College of Marine Life Sciences and Frontiers Science Center for Deep Ocean Multispheres and Earth System, Ocean University of China, Qingdao 266003, China
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28
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Swainsbury DJK, Qian P, Jackson PJ, Faries KM, Niedzwiedzki DM, Martin EC, Farmer DA, Malone LA, Thompson RF, Ranson NA, Canniffe DP, Dickman MJ, Holten D, Kirmaier C, Hitchcock A, Hunter CN. Structures of Rhodopseudomonas palustris RC-LH1 complexes with open or closed quinone channels. SCIENCE ADVANCES 2021; 7:7/3/eabe2631. [PMID: 33523887 PMCID: PMC7806223 DOI: 10.1126/sciadv.abe2631] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Accepted: 11/18/2020] [Indexed: 05/23/2023]
Abstract
The reaction-center light-harvesting complex 1 (RC-LH1) is the core photosynthetic component in purple phototrophic bacteria. We present two cryo-electron microscopy structures of RC-LH1 complexes from Rhodopseudomonas palustris A 2.65-Å resolution structure of the RC-LH114-W complex consists of an open 14-subunit LH1 ring surrounding the RC interrupted by protein-W, whereas the complex without protein-W at 2.80-Å resolution comprises an RC completely encircled by a closed, 16-subunit LH1 ring. Comparison of these structures provides insights into quinone dynamics within RC-LH1 complexes, including a previously unidentified conformational change upon quinone binding at the RC QB site, and the locations of accessory quinone binding sites that aid their delivery to the RC. The structurally unique protein-W prevents LH1 ring closure, creating a channel for accelerated quinone/quinol exchange.
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Affiliation(s)
- David J K Swainsbury
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield, S10 2TN, UK.
| | - Pu Qian
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield, S10 2TN, UK
- Materials and Structural Analysis, Thermo Fisher Scientific, Achtseweg Noord 5, 5651 GG Eindhoven, Netherlands
| | - Philip J Jackson
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield, S10 2TN, UK
- Department of Chemical and Biological Engineering, University of Sheffield, Sheffield, S1 3JD, UK
| | - Kaitlyn M Faries
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Dariusz M Niedzwiedzki
- Center for Solar Energy and Energy Storage, Washington University in St. Louis, St. Louis, MO 63130, USA
- Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Elizabeth C Martin
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield, S10 2TN, UK
| | - David A Farmer
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield, S10 2TN, UK
| | - Lorna A Malone
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield, S10 2TN, UK
| | - Rebecca F Thompson
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, University of Leeds, Leeds, LS2 9JT, UK
| | - Neil A Ranson
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, University of Leeds, Leeds, LS2 9JT, UK
| | - Daniel P Canniffe
- Department of Biochemistry and Systems Biology, Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool, L69 7ZB, UK
| | - Mark J Dickman
- Department of Chemical and Biological Engineering, University of Sheffield, Sheffield, S1 3JD, UK
| | - Dewey Holten
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Christine Kirmaier
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Andrew Hitchcock
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield, S10 2TN, UK
| | - C Neil Hunter
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield, S10 2TN, UK.
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29
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Liang B, Zhao Y, Yang J. Recent Advances in Developing Artificial Autotrophic Microorganism for Reinforcing CO 2 Fixation. Front Microbiol 2020; 11:592631. [PMID: 33240247 PMCID: PMC7680860 DOI: 10.3389/fmicb.2020.592631] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Accepted: 10/21/2020] [Indexed: 11/13/2022] Open
Abstract
With the goal of achieving carbon sequestration, emission reduction and cleaner production, biological methods have been employed to convert carbon dioxide (CO2) into fuels and chemicals. However, natural autotrophic organisms are not suitable cell factories due to their poor carbon fixation efficiency and poor growth rate. Heterotrophic microorganisms are promising candidates, since they have been proven to be efficient biofuel and chemical production chassis. This review first briefly summarizes six naturally occurring CO2 fixation pathways, and then focuses on recent advances in artificially designing efficient CO2 fixation pathways. Moreover, this review discusses the transformation of heterotrophic microorganisms into hemiautotrophic microorganisms and delves further into fully autotrophic microorganisms (artificial autotrophy) by use of synthetic biological tools and strategies. Rapid developments in artificial autotrophy have laid a solid foundation for the development of efficient carbon fixation cell factories. Finally, this review highlights future directions toward large-scale applications. Artificial autotrophic microbial cell factories need further improvements in terms of CO2 fixation pathways, reducing power supply, compartmentalization and host selection.
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Affiliation(s)
- Bo Liang
- Energy-rich Compounds Production by Photosynthetic Carbon Fixation Research Center, Qingdao Agricultural University, Qingdao, China
- Shandong Key Lab of Applied Mycology, College of Life Sciences, Qingdao Agricultural University, Qingdao, China
| | - Yukun Zhao
- Pony Testing International Group, Qingdao, China
| | - Jianming Yang
- Energy-rich Compounds Production by Photosynthetic Carbon Fixation Research Center, Qingdao Agricultural University, Qingdao, China
- Shandong Key Lab of Applied Mycology, College of Life Sciences, Qingdao Agricultural University, Qingdao, China
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30
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Orf GS, Redding KE. Perturbation of the primary acceptor chlorophyll site in the heliobacterial reaction center by coordinating amino acid substitution. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2020; 1862:148324. [PMID: 33039349 DOI: 10.1016/j.bbabio.2020.148324] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Revised: 10/01/2020] [Accepted: 10/05/2020] [Indexed: 11/19/2022]
Abstract
All known Type I photochemical reaction center protein complexes contain a form of the pigment chlorophyll a in their primary electron acceptor site (termed ec3). In the reaction center from the primitive heliobacteria (HbRC), all of the pigment cofactors are bacteriochlorophyll g except in the ec3 sites, which contain 81-hydroxychlorophyll a. To explore the energetic flexibility of this site, we performed site-directed mutagenesis on two of the amino acids of the PshA core polypeptide responsible for coordinating the 81-hydroxychlorophyll a. These two amino acids are serine-545, which coordinates the central Mg(II) through an intermediary water molecule, and serine-553, which participates in a hydrogen bond with the 131-keto O atom. Mutagenesis of serine-545 to histidine (S545H) changes how the chlorophyll's central Mg(II) is coordinated, with the result of decreasing the chlorophyll's site energy. Mutagenesis of serine-545 to methionine (S545M), which was made to mimic the ec3 site of Photosystem I, abolishes chlorophyll binding and charge separation altogether. Mutagenesis of serine-553 to alanine (S553A) removes the aforementioned hydrogen bond, increasing the site energy of the chlorophyll. In the S545H and S553A mutants, the forward and reverse electron transfer rates from ec3 are both faster. This coincides with a decrease in both the quantum yield of initial charge separation and the overall photochemical quantum yield. Taken together, these data indicate that wild-type HbRC is optimized for overall photochemical efficiency, rather than just for maximizing the forward electron transfer rate. The necessity for a chlorophyll a derivative at the ec3 site is also discussed.
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Affiliation(s)
- Gregory S Orf
- Center for Bioenergy and Photosynthesis, School of Molecular Sciences, Arizona State University, Tempe, AZ 85287, USA
| | - Kevin E Redding
- Center for Bioenergy and Photosynthesis, School of Molecular Sciences, Arizona State University, Tempe, AZ 85287, USA.
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31
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Quinone transport in the closed light-harvesting 1 reaction center complex from the thermophilic purple bacterium Thermochromatium tepidum. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2020; 1862:148307. [PMID: 32926863 DOI: 10.1016/j.bbabio.2020.148307] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 07/11/2020] [Revised: 09/03/2020] [Accepted: 09/09/2020] [Indexed: 11/22/2022]
Abstract
Redox-active quinones play essential roles in efficient light energy conversion in type-II reaction centers of purple phototrophic bacteria. In the light-harvesting 1 reaction center (LH1-RC) complex of purple bacteria, QB is converted to QBH2 upon light-induced reduction and QBH2 is transported to the quinone pool in the membrane through the LH1 ring. In the purple bacterium Rhodobacter sphaeroides, the C-shaped LH1 ring contains a gap for quinone transport. In contrast, the thermophilic purple bacterium Thermochromatium (Tch.) tepidum has a closed O-shaped LH1 ring that lacks a gap, and hence the mechanism of photosynthetic quinone transport is unclear. Here we detected light-induced Fourier transform infrared (FTIR) signals responsible for changes of QB and its binding site that accompany photosynthetic quinone reduction in Tch. tepidum and characterized QB and QBH2 marker bands based on their 15N- and 13C-isotopic shifts. Quinone exchanges were monitored using reconstituted photosynthetic membranes comprised of solubilized photosynthetic proteins, membrane lipids, and exogenous ubiquinone (UQ) molecules. In combination with 13C-labeling of the LH1-RC and replacement of native UQ8 by ubiquinones of different tail lengths, we demonstrated that quinone exchanges occur efficiently within the hydrophobic environment of the lipid membrane and depend on the side chain length of UQ. These results strongly indicate that unlike the process in Rba. sphaeroides, quinone transport in Tch. tepidum occurs through the size-restricted hydrophobic channels in the closed LH1 ring and are consistent with structural studies that have revealed narrow hydrophobic channels in the Tch. tepidum LH1 transmembrane region.
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32
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Abstract
Photosynthetic membranes are typically densely packed with proteins, and this is crucial for their function in efficient trapping of light energy. Despite being crowded with protein, the membranes are fluid systems in which proteins and smaller molecules can diffuse. Fluidity is also crucial for photosynthetic function, as it is essential for biogenesis, electron transport, and protein redistribution for functional regulation. All photosynthetic membranes seem to maintain a delicate balance between crowding, order, and fluidity. How does this work in phototrophic bacteria? In this review, we focus on two types of intensively studied bacterial photosynthetic membranes: the chromatophore membranes of purple bacteria and the thylakoid membranes of cyanobacteria. Both systems are distinct from the plasma membrane, and both have a distinctive protein composition that reflects their specialized roles. Chromatophores are formed from plasma membrane invaginations, while thylakoid membranes appear to be an independent intracellular membrane system. We discuss the techniques that can be applied to study the organization and dynamics of these membrane systems, including electron microscopy techniques, atomic force microscopy, and many variants of fluorescence microscopy. We go on to discuss the insights that havebeen acquired from these techniques, and the role of membrane dynamics in the physiology of photosynthetic membranes. Membrane dynamics on multiple timescales are crucial for membrane function, from electron transport on timescales of microseconds to milliseconds to regulation and biogenesis on timescales of minutes to hours. We emphasize the open questions that remain in the field.
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Affiliation(s)
- Conrad W. Mullineaux
- School of Biological and Chemical Sciences, Queen Mary University of London, London E1 4NS, United Kingdom
| | - Lu-Ning Liu
- Institute of Integrative Biology, University of Liverpool, Liverpool L69 7ZB, United Kingdom
- College of Marine Life Sciences, and Frontiers Science Center for Deep Ocean Multispheres and Earth System, Ocean University of China, Qingdao 266003, China
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33
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Maróti P, Kovács IA, Kis M, Smart JL, Iglói F. Correlated clusters of closed reaction centers during induction of intact cells of photosynthetic bacteria. Sci Rep 2020; 10:14012. [PMID: 32814810 PMCID: PMC7438532 DOI: 10.1038/s41598-020-70966-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2020] [Accepted: 07/29/2020] [Indexed: 01/18/2023] Open
Abstract
Antenna systems serve to absorb light and to transmit excitation energy to the reaction center (RC) in photosynthetic organisms. As the emitted (bacterio)chlorophyll fluorescence competes with the photochemical utilization of the excitation, the measured fluorescence yield is informed by the migration of the excitation in the antenna. In this work, the fluorescence yield concomitant with the oxidized dimer (P+) of the RC were measured during light excitation (induction) and relaxation (in the dark) for whole cells of photosynthetic bacterium Rhodobacter sphaeroides lacking cytochrome c2 as natural electron donor to P+ (mutant cycA). The relationship between the fluorescence yield and P+ (fraction of closed RC) showed deviations from the standard Joliot-Lavergne-Trissl model: (1) the hyperbola is not symmetric and (2) exhibits hysteresis. These phenomena originate from the difference between the delays of fluorescence relative to P+ kinetics during induction and relaxation, and in structural terms from the non-random distribution of the closed RCs during induction. The experimental findings are supported by Monte Carlo simulations and by results from statistical physics based on random walk approximations of the excitation in the antenna. The applied mathematical treatment demonstrates the generalization of the standard theory and sets the stage for a more adequate description of the long-debated kinetics of fluorescence and of the delicate control and balance between efficient light harvest and photoprotection in photosynthetic organisms.
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Affiliation(s)
- Péter Maróti
- Department of Medical Physics and Informatics, Szeged University, Rerrich Béla tér 1., 6720, Szeged, Hungary.
| | - István A Kovács
- Department of Physics and Astronomy, Northwestern University, Evanston, IL, 60208-3112, USA
- Wigner Research Centre for Physics, Institute for Solid State Physics and Optics, P.O. Box 49, 1525, Budapest, Hungary
- Department of Network and Data Science, Central European University, Budapest, 1051, Hungary
| | - Mariann Kis
- Department of Medical Physics and Informatics, Szeged University, Rerrich Béla tér 1., 6720, Szeged, Hungary
| | - James L Smart
- Department of Biological Sciences, University of Tennessee at Martin, Martin, TN, 38238, USA
| | - Ferenc Iglói
- Wigner Research Centre for Physics, Institute for Solid State Physics and Optics, P.O. Box 49, 1525, Budapest, Hungary
- Institute of Theoretical Physics, Szeged University, 6720, Szeged, Hungary
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Gardiner AT, Nguyen-Phan TC, Cogdell RJ. A comparative look at structural variation among RC-LH1 'Core' complexes present in anoxygenic phototrophic bacteria. PHOTOSYNTHESIS RESEARCH 2020; 145:83-96. [PMID: 32430765 PMCID: PMC7423801 DOI: 10.1007/s11120-020-00758-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2020] [Accepted: 05/10/2020] [Indexed: 05/30/2023]
Abstract
All purple photosynthetic bacteria contain RC-LH1 'Core' complexes. The structure of this complex from Rhodobacter sphaeroides, Rhodopseudomonas palustris and Thermochromatium tepidum has been solved using X-ray crystallography. Recently, the application of single particle cryo-EM has revolutionised structural biology and the structure of the RC-LH1 'Core' complex from Blastochloris viridis has been solved using this technique, as well as the complex from the non-purple Chloroflexi species, Roseiflexus castenholzii. It is apparent that these structures are variations on a theme, although with a greater degree of structural diversity within them than previously thought. Furthermore, it has recently been discovered that the only phototrophic representative from the phylum Gemmatimonadetes, Gemmatimonas phototrophica, also contains a RC-LH1 'Core' complex. At present only a low-resolution EM-projection map exists but this shows that the Gemmatimonas phototrophica complex contains a double LH1 ring. This short review compares these different structures and looks at the functional significance of these variations from two main standpoints: energy transfer and quinone exchange.
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Affiliation(s)
- Alastair T Gardiner
- Institute of Molecular, Cellular and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, G12 8QQ, UK.
- Laboratory of Anoxygenic Phototrophs, Centre Algatech, Institute of Microbiology of the Czech Academy of Sciences, Novohradska 237, 379 01, Třeboň, Czech Republic.
| | - Tu C Nguyen-Phan
- Institute of Molecular, Cellular and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, G12 8QQ, UK
| | - Richard J Cogdell
- Institute of Molecular, Cellular and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, G12 8QQ, UK
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Shi Y, Xin Y, Wang C, Blankenship RE, Sun F, Xu X. Cryo-EM structures of the air-oxidized and dithionite-reduced photosynthetic alternative complex III from Roseiflexus castenholzii. SCIENCE ADVANCES 2020; 6:eaba2739. [PMID: 32832681 PMCID: PMC7439408 DOI: 10.1126/sciadv.aba2739] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2020] [Accepted: 06/11/2020] [Indexed: 05/27/2023]
Abstract
Alternative complex III (ACIII) is a multisubunit quinol:electron acceptor oxidoreductase that couples quinol oxidation with transmembrane proton translocation in both the respiratory and photosynthetic electron transport chains of bacteria. The coupling mechanism, however, is poorly understood. Here, we report the cryo-EM structures of air-oxidized and dithionite-reduced ACIII from the photosynthetic bacterium Roseiflexus castenholzii at 3.3- and 3.5-Å resolution, respectively. We identified a menaquinol binding pocket and an electron transfer wire comprising six hemes and four iron-sulfur clusters that is capable of transferring electrons to periplasmic acceptors. We detected a proton translocation passage in which three strictly conserved, mid-passage residues are likely essential for coupling the redox-driven proton translocation across the membrane. These results allow us to propose a previously unrecognized coupling mechanism that links the respiratory and photosynthetic functions of ACIII. This study provides a structural basis for further investigation of the energy transformation mechanisms in bacterial photosynthesis and respiration.
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Affiliation(s)
- Yang Shi
- National Laboratory of Biomacromolecules, National Center of Protein Science-Beijing, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yueyong Xin
- Hangzhou Normal University, 2318 Yuhangtang Road, Cangqian, Yuhang District, Hangzhou 311121, Zhejiang Province, China
- Photosynthesis Research Center, College of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou 311121, Zhejiang, China
| | - Chao Wang
- Hangzhou Normal University, 2318 Yuhangtang Road, Cangqian, Yuhang District, Hangzhou 311121, Zhejiang Province, China
| | - Robert E. Blankenship
- Departments of Biology and Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Fei Sun
- National Laboratory of Biomacromolecules, National Center of Protein Science-Beijing, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
- University of Chinese Academy of Sciences, Beijing 100049, China
- Center for Biological Imaging, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Xiaoling Xu
- Hangzhou Normal University, 2318 Yuhangtang Road, Cangqian, Yuhang District, Hangzhou 311121, Zhejiang Province, China
- Photosynthesis Research Center, College of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou 311121, Zhejiang, China
- Key Laboratory of Aging and Cancer Biology of Zhejiang Province, School of Medicine and The Affiliated Hospital, Hangzhou Normal University, Hangzhou 311121, Zhejiang, China
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Jun D, Richardson-Sanchez T, Mahey A, Murphy MEP, Fernandez RC, Beatty JT. Introduction of the Menaquinone Biosynthetic Pathway into Rhodobacter sphaeroides and de Novo Synthesis of Menaquinone for Incorporation into Heterologously Expressed Integral Membrane Proteins. ACS Synth Biol 2020; 9:1190-1200. [PMID: 32271543 DOI: 10.1021/acssynbio.0c00066] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Quinones are redox-active molecules that transport electrons and protons in organelles and cell membranes during respiration and photosynthesis. In addition to the fundamental importance of these processes in supporting life, there has been considerable interest in exploiting their mechanisms for diverse applications ranging from medical advances to innovative biotechnologies. Such applications include novel treatments to target pathogenic bacterial infections and fabricating biohybrid solar cells as an alternative renewable energy source. Ubiquinone (UQ) is the predominant charge-transfer mediator in both respiration and photosynthesis. Other quinones, such as menaquinone (MK), are additional or alternative redox mediators, for example in bacterial photosynthesis of species such as Thermochromatium tepidum and Chloroflexus aurantiacus. Rhodobacter sphaeroides has been used extensively to study electron transfer processes, and recently as a platform to produce integral membrane proteins from other species. To expand the diversity of redox mediators in R. sphaeroides, nine Escherichia coli genes encoding the synthesis of MK from chorismate and polyprenyl diphosphate were assembled into a synthetic operon in a newly designed expression plasmid. We show that the menFDHBCE, menI, menA, and ubiE genes are sufficient for MK synthesis when expressed in R. sphaeroides cells, on the basis of high performance liquid chromatography and mass spectrometry. The T. tepidum and C. aurantiacus photosynthetic reaction centers produced in R. sphaeroides were found to contain MK. We also measured in vitro charge recombination kinetics of the T. tepidum reaction center to demonstrate that the MK is redox-active and incorporated into the QA pocket of this heterologously expressed reaction center.
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Affiliation(s)
- Daniel Jun
- Department of Microbiology and Immunology, University of British Columbia, 2350 Health Sciences Mall, Vancouver, British Columbia V6T 1Z3, Canada
| | - Tomas Richardson-Sanchez
- Department of Microbiology and Immunology, University of British Columbia, 2350 Health Sciences Mall, Vancouver, British Columbia V6T 1Z3, Canada
| | - Amita Mahey
- Department of Microbiology and Immunology, University of British Columbia, 2350 Health Sciences Mall, Vancouver, British Columbia V6T 1Z3, Canada
| | - Michael E. P. Murphy
- Department of Microbiology and Immunology, University of British Columbia, 2350 Health Sciences Mall, Vancouver, British Columbia V6T 1Z3, Canada
| | - Rachel C. Fernandez
- Department of Microbiology and Immunology, University of British Columbia, 2350 Health Sciences Mall, Vancouver, British Columbia V6T 1Z3, Canada
| | - J. Thomas Beatty
- Department of Microbiology and Immunology, University of British Columbia, 2350 Health Sciences Mall, Vancouver, British Columbia V6T 1Z3, Canada
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Miller LC, Zhao L, Canniffe DP, Martin D, Liu LN. Unfolding pathway and intermolecular interactions of the cytochrome subunit in the bacterial photosynthetic reaction center. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2020; 1861:148204. [PMID: 32305414 PMCID: PMC7322399 DOI: 10.1016/j.bbabio.2020.148204] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Revised: 03/15/2020] [Accepted: 04/14/2020] [Indexed: 11/25/2022]
Abstract
Precise folding of photosynthetic proteins and organization of multicomponent assemblies to form functional entities are fundamental to efficient photosynthetic electron transfer. The bacteriochlorophyll b-producing purple bacterium Blastochloris viridis possesses a simplified photosynthetic apparatus. The light-harvesting (LH) antenna complex surrounds the photosynthetic reaction center (RC) to form the RC-LH1 complex. A non-membranous tetraheme cytochrome (4Hcyt) subunit is anchored at the periplasmic surface of the RC, functioning as the electron donor to transfer electrons from mobile electron carriers to the RC. Here, we use atomic force microscopy (AFM) and single-molecule force spectroscopy (SMFS) to probe the long-range organization of the photosynthetic apparatus from Blc. viridis and the unfolding pathway of the 4Hcyt subunit in its native supramolecular assembly with its functional partners. AFM images reveal that the RC-LH1 complexes are densely organized in the photosynthetic membranes, with restricted lateral protein diffusion. Unfolding of the 4Hcyt subunit represents a multi-step process and the unfolding forces of the 4Hcyt α-helices are approximately 121 picoNewtons. Pulling of 4Hcyt could also result in the unfolding of the RC L subunit that binds with the N-terminus of 4Hcyt, suggesting strong interactions between RC subunits. This study provides new insights into the protein folding and interactions of photosynthetic multicomponent complexes, which are essential for their structural and functional integrity to conduct photosynthetic electron flow. AFM and single-molecule force spectroscopy reveal the membrane organization and unfolding process of Blastochloris viridis RC RC-light-harvesting 1 complexes are densely organized in photosynthetic membranes, with restricted lateral diffusion Unfolding of the non-membranous cytochrome (4Hcyt) subunit represents a multi-step process; The average unfolding forces of the 4Hcyt α-helices are ~121 pN; Pulling of 4Hcyt from the RC suggests strong interactions (> 150 pN) between 4Hcyt and L subunits in the RC structure.
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Affiliation(s)
- Leanne C Miller
- Institute of Integrative Biology, University of Liverpool, Liverpool L69 7ZB, United Kingdom; Department of Physics, University of Liverpool, Liverpool L69 7ZE, United Kingdom
| | - Longsheng Zhao
- Institute of Integrative Biology, University of Liverpool, Liverpool L69 7ZB, United Kingdom; State Key Laboratory of Microbial Technology, Marine Biotechnology Research Center, Shandong University, Qingdao 266237, China; Laboratory for Marine Biology and Biotechnology, Pilot National Laboratory for Marine Science and Technology, Qingdao 266237, China
| | - Daniel P Canniffe
- Institute of Integrative Biology, University of Liverpool, Liverpool L69 7ZB, United Kingdom
| | - David Martin
- Department of Physics, University of Liverpool, Liverpool L69 7ZE, United Kingdom
| | - Lu-Ning Liu
- Institute of Integrative Biology, University of Liverpool, Liverpool L69 7ZB, United Kingdom; College of Marine Life Sciences, and Frontiers Science Center for Deep Ocean Multispheres and Earth System, Ocean University of China, Qingdao 266003, China.
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38
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Wang C, Xin Y, Min Z, Qi J, Zhang C, Xu X. Structural basis underlying the electron transfer features of a blue copper protein auracyanin from the photosynthetic bacterium Roseiflexus castenholzii. PHOTOSYNTHESIS RESEARCH 2020; 143:301-314. [PMID: 31933173 DOI: 10.1007/s11120-020-00709-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2019] [Accepted: 01/07/2020] [Indexed: 06/10/2023]
Abstract
Auracyanin (Ac) is a blue copper protein that mediates the electron transfer between Alternative Complex III (ACIII) and downstream electron acceptors in both fort chains of filamentous anoxygenic phototrophs. Here, we extracted and purified the air-oxidized RfxAc from the photoheterotrophically grown Roseiflexus castenholzii, and we illustrated the structural basis underlying its electron transferring features. Spectroscopic and enzymatic analyses demonstrated the reduction of air-oxidized RfxAc by the ACIII upon oxidation of menaquinol-4 and menaquinol-7. Crystal structures of the air-oxidized and Na-dithionite-reduced RfxAc at 2.2 and 2.0 Å resolutions, respectively, showed that the copper ions are coordinated by His77, His146, Cys141, and Met151 in minor different geometries. The Cu1-Sδ bond length increase of Met151, and the electron density Fourier differences at Cu1 and His77 demonstrated their essential roles in the dithionite-induced reduction. Structural comparisons further revealed that the RfxAc contains a Chloroflexus aurantiacus Ac-A-like copper binding pocket and a hydrophobic patch surrounding the exposed edge of His146 imidazole, as well as an Ac-B-like Ser- and Thr-rich polar patch located at a different site on the surface. These spectroscopic and structural features allow RfxAc to mediate electron transfers between the ACIII and redox partners different from those of Ac-A and Ac-B. These results provide a structural basis for further investigating the electron transfer and energy transformation mechanism of bacterial photosynthesis, and the diversity and evolution of electron transport chains.
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Affiliation(s)
- Chao Wang
- Institute of Ageing Research, School of Medicine, Hangzhou Normal University, Hangzhou, 311121, Zhejiang, China
| | - Yueyong Xin
- College of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou, 311121, Zhejiang, China
- Photosynthesis Research Center, College of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou, 311121, Zhejiang, China
| | - Zhenzhen Min
- Institute of Ageing Research, School of Medicine, Hangzhou Normal University, Hangzhou, 311121, Zhejiang, China
| | - Junjie Qi
- College of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou, 311121, Zhejiang, China
| | - Chenyun Zhang
- Institute of Ageing Research, School of Medicine, Hangzhou Normal University, Hangzhou, 311121, Zhejiang, China
| | - Xiaoling Xu
- Institute of Ageing Research, School of Medicine, Hangzhou Normal University, Hangzhou, 311121, Zhejiang, China.
- Institute of Cardiovascular Disease Research, The Affiliated Hospital of Hangzhou Normal University, Hangzhou, 311121, Zhejiang, China.
- Key Laboratory of Aging and Cancer Biology of Zhejiang Province, Hangzhou Normal University School of Medicine, Hangzhou, 311121, Zhejiang, China.
- Photosynthesis Research Center, College of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou, 311121, Zhejiang, China.
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Ward LM, Cardona T, Holland-Moritz H. Evolutionary Implications of Anoxygenic Phototrophy in the Bacterial Phylum Candidatus Eremiobacterota (WPS-2). Front Microbiol 2019; 10:1658. [PMID: 31396180 PMCID: PMC6664022 DOI: 10.3389/fmicb.2019.01658] [Citation(s) in RCA: 61] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2019] [Accepted: 07/04/2019] [Indexed: 12/15/2022] Open
Abstract
Genome-resolved environmental metagenomic sequencing has uncovered substantial previously unrecognized microbial diversity relevant for understanding the ecology and evolution of the biosphere, providing a more nuanced view of the distribution and ecological significance of traits including phototrophy across diverse niches. Recently, the capacity for bacteriochlorophyll-based anoxygenic photosynthesis has been proposed in the uncultured bacterial WPS-2 phylum (recently proposed as Candidatus Eremiobacterota) that are in close association with boreal moss. Here, we use phylogenomic analysis to investigate the diversity and evolution of phototrophic WPS-2. We demonstrate that phototrophic WPS-2 show significant genetic and metabolic divergence from other phototrophic and non-phototrophic lineages. The genomes of these organisms encode a new family of anoxygenic Type II photochemical reaction centers and other phototrophy-related proteins that are both phylogenetically and structurally distinct from those found in previously described phototrophs. We propose the name Candidatus Baltobacterales for the order-level aerobic WPS-2 clade which contains phototrophic lineages, from the Greek for "bog" or "swamp," in reference to the typical habitat of phototrophic members of this clade.
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Affiliation(s)
- Lewis M. Ward
- Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA, United States
| | - Tanai Cardona
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Hannah Holland-Moritz
- Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, CO, United States
- Department of Ecology and Evolutionary Biology, University of Colorado Boulder, Boulder, CO, United States
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Yu LJ, Suga M, Wang-Otomo ZY, Shen JR. Novel features of LH1-RC from Thermochromatium tepidum revealed from its atomic resolution structure. FEBS J 2018; 285:4359-4366. [PMID: 30328658 DOI: 10.1111/febs.14679] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Accepted: 10/09/2018] [Indexed: 11/28/2022]
Abstract
Light-harvesting-1 (LH1)-reaction center (RC) super-complex is a membrane protein-pigment complex existing in purple photosynthetic bacteria, where LH1 absorbs light energy and transfers them rapidly and efficiently to RC to initiate the charge separation and electron transfer reactions. The structure of LH1-RC has been reported at relatively low resolutions from several different species of bacteria previously, but was solved at an atomic resolution recently from a thermophilic photosynthetic bacterium Thermochromatium tepidum. This high-resolution structure revealed the detailed organization of the super-complex including a number of unique features that are important for its functioning, such as a more intact RC structure, transporting routes for quinones to replace the bound QB as well as for the in-and-out of the closed LH1 ring, detailed coordinating environment of the Ca2+ ions in LH1 important for the remarkable red shift of the absorption spectrum, as well as for the enhanced thermostability. These results thus greatly advance our understanding on the mechanisms of energy transfer, quinone exchange, the red shift in the LH1-Qy transition and the enhanced thermal stability, in this super-complex.
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Affiliation(s)
- Long-Jiang Yu
- Research Institute for Interdisciplinary Science, Graduate School of Natural Science and Technology, Okayama University, Japan
| | - Michihiro Suga
- Research Institute for Interdisciplinary Science, Graduate School of Natural Science and Technology, Okayama University, Japan
| | | | - Jian-Ren Shen
- Research Institute for Interdisciplinary Science, Graduate School of Natural Science and Technology, Okayama University, Japan
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