Cryo-EM Structure of the Photosynthetic LH1-RC Complex from <i>Rhodospirillum rubrum</i>

Tani, Kazuhide; Kanno, Ryo; Ji, Xuan-Cheng; Hall, Malgorzata; Yu, Long-Jiang; Kimura, Yukihiro; Madigan, Michael T.; Mizoguchi, Akira; Humbel, Bruno M.; Wang-Otomo, Zheng-Yu

doi:10.1101/2021.05.30.446358

Cited by 6 publications

(8 citation statements)

References 31 publications

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“…On the other hand, the process parameters require optimization. Therefore, based on original research [9,10,28,31,32], model broths were prepared. The initial dark fermentation broth was composed of a sterile minimal medium Buffered Peptone Water (Biomaxima, Gdańsk, Poland) and lignocellulosic biomass hydrolysates, as the sole carbon source for hydrogen-generating anaerobic microorganisms; i.e., Enterobacter aerogenes ATCC 13048 [10].…”

Section: Model Photo Fermentation Broth Characterizationmentioning

confidence: 99%

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Management of Dark Fermentation Broth via Bio Refining and Photo Fermentation

et al. 2021

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Lignocellulose and starch-based raw materials are often applied in the investigations regarding biohydrogen generation using dark fermentation. Management of the arising post-fermentation broth becomes a problem. The Authors proposed sequential processes, to improve the efficiency of both hydrogen generation and by-products management carried under model conditions. During the proposed procedure, the simple sugars remaining in broth are converted into organic acids, and when these products are used as substrates for the photo fermentation process. To enhance the broth management also conditions promoting Deep Eutectic Solvents (DES) precursors synthesis are simultaneously applied. Application of Box-Behnken design allows defining of the optimal conditions for conversion to DESs precursors. During the procedure hydrogen was obtained, the concentration of hydrogen in the photo fermentation reached up to 819 mL H2/L medium/7 d, depending on the broth type, i.e., when the broth was optimized for formic acid concentration. The DESs precursors were separated and engaged in DESs synthesis. To confirm the formation of the DESs, FT-IR analyses were performed. The Chemical Oxygen Demand of post-fermentation broths after dark fermentation optimized for formic acid was reduced by ca. 82%. The proposed procedure can be successfully used as a method of post-fermentation broth management.

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Section: Model Photo Fermentation Broth Characterizationmentioning

confidence: 99%

“…Rhodospirillum rubrum is a frequently studied species [31], exhibiting unique nitrogenase activity, reducing both molecular nitrogen and protons to molecular hydrogen. In addition to the ability to bind carbon dioxide, it can bind nitrogen.…”

Section: Photo Fermentationmentioning

confidence: 99%

Management of Dark Fermentation Broth via Bio Refining and Photo Fermentation

et al. 2021

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“…The compositions and architectures of RC–LH1 supercomplexes exhibit a diversity among various bacterial species 2 . Many RC–LH1 complexes occur as monomers, in which the RC is encircled by a closed LH1 ring of 16 αβ-heterodimers 7 – 11 , or an open LH1 ring of 15–16 αβ-polypeptides with a gap formed by specific transmembrane (TM) polypeptides 12 – 17 . The Rhodobacter genus is characterized by the presence of a PufX polypeptide in RC–LH1, which functions as a molecular cross brace to stabilize the monomeric core complex of Rhodobacter ( Rba .)…”

Section: Introductionmentioning

confidence: 99%

Structural basis for the assembly and quinone transport mechanisms of the dimeric photosynthetic RC–LH1 supercomplex

et al. 2022

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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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“…The recent determination of several LH1 structures using cryo-EM provides opportunities for further exploration. 19 Our previous study on LH2 demonstrated that the absorption spectrum of B850 cannot be replicated by the conventional exciton model (referred to as the monomer exciton model in this paper). 32 To address this issue, we developed a dimer exciton model, wherein the BChl a dimer was treated as a unified fragment.…”

Section: Introductionmentioning

confidence: 79%

Prominent Role of Charge Transfer in the Spectral Tuning of Photosynthetic Light-Harvesting I Complex

Fujimoto,

Tsuji,

Wang-Otomo

et al. 2024

ACS Phys. Chem Au

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Purple bacteria possess two ring-shaped protein complexes, light-harvesting 1 (LH1) and 2 (LH2), both of which function as antennas for solar energy utilization for photosynthesis but exhibit distinct absorption properties. The two antennas have differing amounts of bacteriochlorophyll (BChl) a; however, their significance in spectral tuning remains elusive. Here, we report a high-precision evaluation of the physicochemical factors contributing to the variation in absorption maxima between LH1 and LH2, namely, BChl a structural distortion, protein electrostatic interaction, excitonic coupling, and charge transfer (CT) effects, as derived from detailed spectral calculations using an extended version of the exciton model, in the model purple bacterium Rhodospirillum rubrum. Spectral analysis confirmed that the electronic structure of the excited state in LH1 extended to the BChl a 16-mer. Further analysis revealed that the LH1-specific redshift (∼61% in energy) is predominantly accounted for by the CT effect resulting from the closer inter-BChl distance in LH1 than in LH2. Our analysis explains how LH1 and LH2, both with chemically identical BChl a chromophores, use distinct physicochemical effects to achieve a progressive redshift from LH2 to LH1, ensuring efficient energy transfer to the reaction center special pair.

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Cryo-EM Structure of the Photosynthetic LH1-RC Complex from Rhodospirillum rubrum

Cited by 6 publications

References 31 publications

Management of Dark Fermentation Broth via Bio Refining and Photo Fermentation

Management of Dark Fermentation Broth via Bio Refining and Photo Fermentation

Structural basis for the assembly and quinone transport mechanisms of the dimeric photosynthetic RC–LH1 supercomplex

Prominent Role of Charge Transfer in the Spectral Tuning of Photosynthetic Light-Harvesting I Complex

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