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Lyratzakis A, Daskalakis V, Xie H, Tsiotis G. The synergy between the PscC subunits for electron transfer to the P 840 special pair in Chlorobaculum tepidum. PHOTOSYNTHESIS RESEARCH 2024; 160:87-96. [PMID: 38625595 PMCID: PMC11108878 DOI: 10.1007/s11120-024-01093-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2023] [Accepted: 03/08/2024] [Indexed: 04/17/2024]
Abstract
The primary photochemical reaction of photosynthesis in green sulfur bacteria occurs in the homodimer PscA core proteins by a special chlorophyll pair. The light induced excited state of the special pair producing P840+ is rapidly reduced by electron transfer from one of the two PscC subunits. Molecular dynamics (MD) simulations are combined with bioinformatic tools herein to provide structural and dynamic insight into the complex between the two PscA core proteins and the two PscC subunits. The microscopic dynamic model involves extensive sampling at atomic resolution and at a cumulative time-scale of 22µs and reveals well defined protein-protein interactions. The membrane complex is composed of the two PscA and the two PscC subunits and macroscopic connections are revealed within a putative electron transfer pathway from the PscC subunit to the special pair P840 located within the PscA subunits. Our results provide a structural basis for understanding the electron transport to the homodimer RC of the green sulfur bacteria. The MD based approach can provide the basis to further probe the PscA-PscC complex dynamics and observe electron transfer therein at the quantum level. Furthermore, the transmembrane helices of the different PscC subunits exert distinct dynamics in the complex.
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Affiliation(s)
- Alexandros Lyratzakis
- Department of Chemistry, School of Science and Engineering, University of Crete, Heraklion, 70013, Greece
| | - Vangelis Daskalakis
- Department of Chemical Engineering, School of Engineering, University of Patras, Rion, Patras, 26504, Greece
| | - Hao Xie
- Max Planck Institute of Biophysics, 60438, Frankfurt am Main, Germany
| | - Georgios Tsiotis
- Department of Chemistry, School of Science and Engineering, University of Crete, Heraklion, 70013, Greece.
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Nelson N. Investigating the Balance between Structural Conservation and Functional Flexibility in Photosystem I. Int J Mol Sci 2024; 25:5073. [PMID: 38791114 PMCID: PMC11121529 DOI: 10.3390/ijms25105073] [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: 02/27/2024] [Revised: 04/16/2024] [Accepted: 04/30/2024] [Indexed: 05/26/2024] Open
Abstract
Photosynthesis, as the primary source of energy for all life forms, plays a crucial role in maintaining the global balance of energy, entropy, and enthalpy in living organisms. Among its various building blocks, photosystem I (PSI) is responsible for light-driven electron transfer, crucial for generating cellular reducing power. PSI acts as a light-driven plastocyanin-ferredoxin oxidoreductase and is situated in the thylakoid membranes of cyanobacteria and the chloroplasts of eukaryotic photosynthetic organisms. Comprehending the structure and function of the photosynthetic machinery is essential for understanding its mode of action. New insights are offered into the structure and function of PSI and its associated light-harvesting proteins, with a specific focus on the remarkable structural conservation of the core complex and high plasticity of the peripheral light-harvesting complexes.
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Affiliation(s)
- Nathan Nelson
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
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Fujii S, Tamiaki H. Self-aggregation of zinc bacteriochlorophyll-d analogs with an acylhydrazone moiety as the 13-keto-carbonyl alternative. Photochem Photobiol 2024. [PMID: 38581225 DOI: 10.1111/php.13949] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2024] [Revised: 03/11/2024] [Accepted: 03/26/2024] [Indexed: 04/08/2024]
Abstract
Zinc methyl 3-hydroxymethyl-pyropheophorbides-a possessing an acylhydrazinylidene group at the 131-position were prepared by chemically modifying chlorophyll-a, which were models of bacteriochlorophyll-d as one of the light-harvesting pigments in photosynthetic green bacteria. Similar to the self-aggregation of natural bacteriochlorophyll-d in the antenna systems called chlorosomes, some of the synthetic models self-aggregated in an aqueous Triton X-100 solution to give red-shifted and broadened visible absorption bands. The newly appeared oligomeric bands were ascribable to the exciton coupling of the chlorin π-systems along the molecular y-axis, leading to intense circular dichroism bands in the red-shifted Qy and Soret regions. The self-aggregation in the aqueous micelle was dependent on the steric size of the terminal substituent at the 13-acylhydrazone moiety. An increase in the length of the oligomethylene chain as the terminal moved the red-shifted Qy maxima to shorter wavelengths, and branched alkyl and benzyl substitutes afforded no more self-aggregates to leave monomeric species in the hydrophobic environment inside the micelle. These results indicated that the acyl groups on the 13-hydrazone as the alternative of the natural 13-ketone regulated the chlorosome-like self-aggregation.
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Affiliation(s)
- Satoru Fujii
- Graduate School of Life Sciences, Ritsumeikan University, Kusatsu, Shiga, Japan
| | - Hitoshi Tamiaki
- Graduate School of Life Sciences, Ritsumeikan University, Kusatsu, Shiga, Japan
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Yasui M, Tamiaki H. Supramolecular chirality in self-assembly of zinc protobacteriochlorophyll-d analogs possessing enantiomeric esterifying groups. Photochem Photobiol Sci 2024; 23:421-434. [PMID: 38265754 DOI: 10.1007/s43630-023-00528-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Accepted: 12/19/2023] [Indexed: 01/25/2024]
Abstract
Zinc 3-hydroxymethyl-pyroprotopheophorbides-a esterified with a chiral secondary alcohol at the 17-propionate residue were prepared as bacteriochlorophyll-d analogs. The synthetic zinc 31-hydroxy-131-oxo-porphyrins self-aggregated in an aqueous Triton X-100 micellar solution to give red-shifted and broadened Soret and Qy absorption bands in comparison with their monomeric bands. The intense, exciton-coupled circular dichroism spectra of their self-aggregates were dependent on the chirality of the esterifying groups. The observation indicated that the self-aggregates based on the J-type stacking of the porphyrin cores were sensitive to the peripheral 17-propionate residues. The supramolecular structures of the present J-aggregates as models of bacteriochlorophyll aggregates in natural chlorosomes were remotely regulated by the esterifying groups.
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Affiliation(s)
- Mizuki Yasui
- Graduate School of Life Sciences, Ritsumeikan University, Kusatsu, Shiga, 525-8577, Japan
| | - Hitoshi Tamiaki
- Graduate School of Life Sciences, Ritsumeikan University, Kusatsu, Shiga, 525-8577, Japan.
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Tsuji JM, Shaw NA, Nagashima S, Venkiteswaran JJ, Schiff SL, Watanabe T, Fukui M, Hanada S, Tank M, Neufeld JD. Anoxygenic phototroph of the Chloroflexota uses a type I reaction centre. Nature 2024; 627:915-922. [PMID: 38480893 PMCID: PMC10972752 DOI: 10.1038/s41586-024-07180-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Accepted: 02/08/2024] [Indexed: 04/01/2024]
Abstract
Scientific exploration of phototrophic bacteria over nearly 200 years has revealed large phylogenetic gaps between known phototrophic groups that limit understanding of how phototrophy evolved and diversified1,2. Here, through Boreal Shield lake water incubations, we cultivated an anoxygenic phototrophic bacterium from a previously unknown order within the Chloroflexota phylum that represents a highly novel transition form in the evolution of photosynthesis. Unlike all other known phototrophs, this bacterium uses a type I reaction centre (RCI) for light energy conversion yet belongs to the same bacterial phylum as organisms that use a type II reaction centre (RCII) for phototrophy. Using physiological, phylogenomic and environmental metatranscriptomic data, we demonstrate active RCI-utilizing metabolism by the strain alongside usage of chlorosomes3 and bacteriochlorophylls4 related to those of RCII-utilizing Chloroflexota members. Despite using different reaction centres, our phylogenomic data provide strong evidence that RCI-utilizing and RCII-utilizing Chloroflexia members inherited phototrophy from a most recent common phototrophic ancestor. The Chloroflexota phylum preserves an evolutionary record of the use of contrasting phototrophic modes among genetically related bacteria, giving new context for exploring the diversification of phototrophy on Earth.
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Affiliation(s)
- J M Tsuji
- University of Waterloo, Waterloo, Ontario, Canada.
- Institute of Low Temperature Science, Hokkaido University, Sapporo, Japan.
- Japan Agency for Marine-Earth Science and Technology, Yokosuka, Japan.
| | - N A Shaw
- University of Waterloo, Waterloo, Ontario, Canada
| | - S Nagashima
- Tokyo Metropolitan University, Tokyo, Japan
- Kanagawa University, Yokohama, Japan
| | - J J Venkiteswaran
- University of Waterloo, Waterloo, Ontario, Canada
- Wilfrid Laurier University, Waterloo, Ontario, Canada
| | - S L Schiff
- University of Waterloo, Waterloo, Ontario, Canada
| | - T Watanabe
- Institute of Low Temperature Science, Hokkaido University, Sapporo, Japan
| | - M Fukui
- Institute of Low Temperature Science, Hokkaido University, Sapporo, Japan
| | - S Hanada
- Tokyo Metropolitan University, Tokyo, Japan
- Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan
| | - M Tank
- Tokyo Metropolitan University, Tokyo, Japan
- Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures GmbH, Braunschweig, Germany
| | - J D Neufeld
- University of Waterloo, Waterloo, Ontario, Canada.
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Kimura A, Kitoh-Nishioka H, Kondo T, Oh-Oka H, Itoh S, Azai C. Experimental and Theoretical Mutation of Exciton States on the Smallest Type-I Photosynthetic Reaction Center Complex of a Green Sulfur Bacterium Chlorobaclum tepidum. J Phys Chem B 2024; 128:731-743. [PMID: 38198639 DOI: 10.1021/acs.jpcb.3c07424] [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: 01/12/2024]
Abstract
The exciton states on the smallest type-I photosynthetic reaction center complex of a green sulfur bacterium Chlorobaculum tepidum (GsbRC) consisting of 26 bacteriochlorophylls a (BChl a) and four chlorophylls a (Chl a) located on the homodimer of two PscA reaction center polypeptides were investigated. This analysis involved the study of exciton states through a combination of theoretical modeling and the genetic removal of BChl a pigments at eight sites. (1) A theoretical model of the pigment assembly exciton state on GsbRC was constructed using Poisson TrESP (P-TrESP) and charge density coupling (CDC) methods based on structural information. The model reproduced the experimentally obtained absorption spectrum, circular dichroism spectrum, and excitation transfer dynamics, as well as explained the effects of mutation. (2) Eight BChl a molecules at different locations on the GsbRC were selectively removed by genetic exchange of the His residue, which ligates the central Mg atom of BChl a, with the Leu residue on either one or two PscAs in the RC. His locations are conserved among all type-I RC plant polypeptide, cyanobacteria, and bacteria amino acid sequences. (3) Purified mutant-GsbRCs demonstrated distinct absorption and fluorescence spectra at 77 K, which were different from each other, suggesting successful pigment removal. (4) The same mutations were applied to the constructed theoretical model to analyze the outcomes of these mutations. (5) The combination of theoretical predictions and experimental mutations based on structural information is a new tool for studying the function and evolution of photosynthetic reaction centers.
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Affiliation(s)
- Akihiro Kimura
- Department of Physics, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
| | - Hirotaka Kitoh-Nishioka
- Department of Energy and Materials, Faculty of Science and Engineering, Kindai University, Osaka 577-8502, Japan
| | - Toru Kondo
- School of Life Science and Technology, Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8550, Japan
| | - Hirozo Oh-Oka
- Department of Biological Sciences, Graduate School of Science, Osaka University, Osaka 560-0043, Japan
| | - Shigeru Itoh
- Department of Physics, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
| | - Chihiro Azai
- Department of Biological Sciences, Faculty of Science and Engineering, Chuo University, Tokyo 112-8551, Japan
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