1
|
Manoj KM, Gideon DA, Parashar A, Nirusimhan V, Annadurai P, Jacob VD, Manekkathodi A. Validating the predictions of murburn model for oxygenic photosynthesis: Analyses of ligand-binding to protein complexes and cross-system comparisons. J Biomol Struct Dyn 2022; 40:11024-11056. [PMID: 34328391 DOI: 10.1080/07391102.2021.1953607] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
In this second half of our treatise on oxygenic photosynthesis, we provide support for the murburn model of the light reaction of photosynthesis and ratify key predictions made in the first part. Molecular docking and visualization of various ligands of quinones/quinols (and their derivatives) with PS II/Cytochrome b6f complexes did not support chartered 2e-transport role of quinols. A broad variety of herbicides did not show any affinity/binding-based rationales for inhibition of photosynthesis. We substantiate the proposal that disubstituted phenolics (perceived as protonophores/uncouplers or affinity-based inhibitors in the classical purview) serve as interfacial modulators of diffusible reactive (oxygen) species or DR(O)S. The DRS-based murburn model is evidenced by the identification of multiple ADP-binding sites on the extra-membraneous projection of protein complexes and structure/distribution of the photo/redox catalysts. With a panoramic comparison of the redox metabolic machinery across diverse organellar/cellular systems, we highlight the ubiquitous one-electron murburn facets (cofactors of porphyrin, flavin, FeS, other metal centers and photo/redox active pigments) that enable a facile harnessing of the utility of DRS. In the summative analyses, it is demonstrated that the murburn model of light reaction explains the structures of membrane supercomplexes recently observed in thylakoids and also accounts for several photodynamic experimental observations and evolutionary considerations. In toto, the work provides a new orientation and impetus to photosynthesis research. Communicated by Ramaswamy H. Sarma.
Collapse
Affiliation(s)
- Kelath Murali Manoj
- RedOx Lab, Department of Life Sciences, Satyamjayatu: The Science & Ethics Foundation, Palakkad District, Kerala, India
| | - Daniel Andrew Gideon
- RedOx Lab, Department of Life Sciences, Satyamjayatu: The Science & Ethics Foundation, Palakkad District, Kerala, India
| | - Abhinav Parashar
- RedOx Lab, Department of Life Sciences, Satyamjayatu: The Science & Ethics Foundation, Palakkad District, Kerala, India
| | - Vijay Nirusimhan
- RedOx Lab, Department of Life Sciences, Satyamjayatu: The Science & Ethics Foundation, Palakkad District, Kerala, India
| | - Pushparaj Annadurai
- RedOx Lab, Department of Life Sciences, Satyamjayatu: The Science & Ethics Foundation, Palakkad District, Kerala, India
| | - Vivian David Jacob
- RedOx Lab, Department of Life Sciences, Satyamjayatu: The Science & Ethics Foundation, Palakkad District, Kerala, India
| | - Afsal Manekkathodi
- RedOx Lab, Department of Life Sciences, Satyamjayatu: The Science & Ethics Foundation, Palakkad District, Kerala, India
| |
Collapse
|
2
|
Molecular electrets – Why do dipoles matter for charge transfer and excited-state dynamics? J Photochem Photobiol A Chem 2020. [DOI: 10.1016/j.jphotochem.2020.112779] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
|
3
|
Geometric and electronic structure of a crystallographically characterized thiolate-ligated binuclear peroxo-bridged cobalt(III) complex. J Biol Inorg Chem 2019; 24:919-926. [PMID: 31342141 DOI: 10.1007/s00775-019-01686-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2019] [Accepted: 07/11/2019] [Indexed: 10/26/2022]
Abstract
In order to shed light on metal-dependent mechanisms for O-O bond cleavage, and its microscopic reverse, we compare herein the electronic and geometric structures of O2-derived binuclear Co(III)- and Mn(III)-peroxo compounds. Binuclear metal peroxo complexes are proposed to form as intermediates during Mn-promoted photosynthetic H2O oxidation, and a Co-containing artificial leaf inspired by nature's photosynthetic H2O oxidation catalyst. Crystallographic characterization of an extremely activated peroxo is made possible by working with substitution-inert, low-spin Co(III). Density functional theory (DFT) calculations show that the frontier orbitals of the Co(III)-peroxo compound differ noticeably from the analogous Mn(III)-peroxo compound. The highest occupied molecular orbital (HOMO) associated with the Co(III)-peroxo is more localized on the peroxo in an antibonding π*(O-O) orbital, whereas the HOMO of the structurally analogous Mn(III)-peroxo is delocalized over both the metal d-orbitals and peroxo π*(O-O) orbital. With low-spin d6 Co(III), filled t2g orbitals prevent π-back-donation from the doubly occupied antibonding π*(O-O) orbital onto the metal ion. This is not the case with high-spin d4 Mn(III), since these orbitals are half-filled. This weakens the peroxo O-O bond of the former relative to the latter.
Collapse
|
4
|
Schwieterman EW, Kiang NY, Parenteau MN, Harman CE, DasSarma S, Fisher TM, Arney GN, Hartnett HE, Reinhard CT, Olson SL, Meadows VS, Cockell CS, Walker SI, Grenfell JL, Hegde S, Rugheimer S, Hu R, Lyons TW. Exoplanet Biosignatures: A Review of Remotely Detectable Signs of Life. ASTROBIOLOGY 2018; 18:663-708. [PMID: 29727196 PMCID: PMC6016574 DOI: 10.1089/ast.2017.1729] [Citation(s) in RCA: 97] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Accepted: 12/10/2017] [Indexed: 05/04/2023]
Abstract
In the coming years and decades, advanced space- and ground-based observatories will allow an unprecedented opportunity to probe the atmospheres and surfaces of potentially habitable exoplanets for signatures of life. Life on Earth, through its gaseous products and reflectance and scattering properties, has left its fingerprint on the spectrum of our planet. Aided by the universality of the laws of physics and chemistry, we turn to Earth's biosphere, both in the present and through geologic time, for analog signatures that will aid in the search for life elsewhere. Considering the insights gained from modern and ancient Earth, and the broader array of hypothetical exoplanet possibilities, we have compiled a comprehensive overview of our current understanding of potential exoplanet biosignatures, including gaseous, surface, and temporal biosignatures. We additionally survey biogenic spectral features that are well known in the specialist literature but have not yet been robustly vetted in the context of exoplanet biosignatures. We briefly review advances in assessing biosignature plausibility, including novel methods for determining chemical disequilibrium from remotely obtainable data and assessment tools for determining the minimum biomass required to maintain short-lived biogenic gases as atmospheric signatures. We focus particularly on advances made since the seminal review by Des Marais et al. The purpose of this work is not to propose new biosignature strategies, a goal left to companion articles in this series, but to review the current literature, draw meaningful connections between seemingly disparate areas, and clear the way for a path forward. Key Words: Exoplanets-Biosignatures-Habitability markers-Photosynthesis-Planetary surfaces-Atmospheres-Spectroscopy-Cryptic biospheres-False positives. Astrobiology 18, 663-708.
Collapse
Affiliation(s)
- Edward W. Schwieterman
- Department of Earth Sciences, University of California, Riverside, California
- NASA Postdoctoral Program, Universities Space Research Association, Columbia, Maryland
- NASA Astrobiology Institute, Virtual Planetary Laboratory Team, Seattle, Washington
- NASA Astrobiology Institute, Alternative Earths Team, Riverside, California
- Blue Marble Space Institute of Science, Seattle, Washington
| | - Nancy Y. Kiang
- NASA Astrobiology Institute, Virtual Planetary Laboratory Team, Seattle, Washington
- NASA Goddard Institute for Space Studies, New York, New York
| | - Mary N. Parenteau
- NASA Astrobiology Institute, Virtual Planetary Laboratory Team, Seattle, Washington
- NASA Ames Research Center, Exobiology Branch, Mountain View, California
| | - Chester E. Harman
- NASA Astrobiology Institute, Virtual Planetary Laboratory Team, Seattle, Washington
- NASA Goddard Institute for Space Studies, New York, New York
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York
| | - Shiladitya DasSarma
- Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, Maryland
- Institute of Marine and Environmental Technology, University System of Maryland, Baltimore, Maryland
| | - Theresa M. Fisher
- School of Earth and Space Exploration, Arizona State University, Tempe, Arizona
| | - Giada N. Arney
- NASA Astrobiology Institute, Virtual Planetary Laboratory Team, Seattle, Washington
- Planetary Systems Laboratory, NASA Goddard Space Flight Center, Greenbelt, Maryland
| | - Hilairy E. Hartnett
- School of Earth and Space Exploration, Arizona State University, Tempe, Arizona
- School of Molecular Sciences, Arizona State University, Tempe, Arizona
| | - Christopher T. Reinhard
- NASA Astrobiology Institute, Alternative Earths Team, Riverside, California
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia
| | - Stephanie L. Olson
- Department of Earth Sciences, University of California, Riverside, California
- NASA Astrobiology Institute, Alternative Earths Team, Riverside, California
| | - Victoria S. Meadows
- NASA Astrobiology Institute, Virtual Planetary Laboratory Team, Seattle, Washington
- Astronomy Department, University of Washington, Seattle, Washington
| | - Charles S. Cockell
- University of Edinburgh School of Physics and Astronomy, Edinburgh, United Kingdom
- UK Centre for Astrobiology, Edinburgh, United Kingdom
| | - Sara I. Walker
- Blue Marble Space Institute of Science, Seattle, Washington
- School of Earth and Space Exploration, Arizona State University, Tempe, Arizona
- Beyond Center for Fundamental Concepts in Science, Arizona State University, Tempe, Arizona
- ASU-Santa Fe Institute Center for Biosocial Complex Systems, Arizona State University, Tempe, Arizona
| | - John Lee Grenfell
- Institut für Planetenforschung (PF), Deutsches Zentrum für Luft und Raumfahrt (DLR), Berlin, Germany
| | - Siddharth Hegde
- Carl Sagan Institute, Cornell University, Ithaca, New York
- Cornell Center for Astrophysics and Planetary Science, Cornell University, Ithaca, New York
| | - Sarah Rugheimer
- Department of Earth and Environmental Sciences, University of St. Andrews, St. Andrews, United Kingdom
| | - Renyu Hu
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California
| | - Timothy W. Lyons
- Department of Earth Sciences, University of California, Riverside, California
- NASA Astrobiology Institute, Alternative Earths Team, Riverside, California
| |
Collapse
|
5
|
Nowicka B, Kruk J. Powered by light: Phototrophy and photosynthesis in prokaryotes and its evolution. Microbiol Res 2016; 186-187:99-118. [PMID: 27242148 DOI: 10.1016/j.micres.2016.04.001] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2015] [Revised: 02/12/2016] [Accepted: 04/01/2016] [Indexed: 11/29/2022]
Abstract
Photosynthesis is a complex metabolic process enabling photosynthetic organisms to use solar energy for the reduction of carbon dioxide into biomass. This ancient pathway has revolutionized life on Earth. The most important event was the development of oxygenic photosynthesis. It had a tremendous impact on the Earth's geochemistry and the evolution of living beings, as the rise of atmospheric molecular oxygen enabled the development of a highly efficient aerobic metabolism, which later led to the evolution of complex multicellular organisms. The mechanism of photosynthesis has been the subject of intensive research and a great body of data has been accumulated. However, the evolution of this process is not fully understood, and the development of photosynthesis in prokaryota in particular remains an unresolved question. This review is devoted to the occurrence and main features of phototrophy and photosynthesis in prokaryotes. Hypotheses concerning the origin and spread of photosynthetic traits in bacteria are also discussed.
Collapse
Affiliation(s)
- Beatrycze Nowicka
- Department of Plant Physiology and Biochemistry, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387 Kraków, Poland.
| | - Jerzy Kruk
- Department of Plant Physiology and Biochemistry, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387 Kraków, Poland.
| |
Collapse
|
6
|
Reprint of PSII manganese cluster: protonation of W2, O5, O4 and His337 in the S1 state explored by combined quantum chemical and electrostatic energy computations. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2014; 1837:1389-94. [PMID: 25065862 DOI: 10.1016/j.bbabio.2014.07.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2013] [Revised: 02/17/2014] [Accepted: 03/29/2014] [Indexed: 11/22/2022]
Abstract
Photosystem II (PSII) is a membrane-bound protein complex that oxidizes water to produce energized protons, which are used to built up a proton gradient across the thylakoidal membrane in the leafs of plants. This light-driven reaction is catalyzed by withdrawing electrons from the Mn₄CaO₅-cluster (Mn-cluster) in four discrete oxidation steps [S₁-(S₄/S₀)] characterized in the Kok-cycle. In order to understand in detail the proton release events and the subsequent translocation of such energized protons, the protonation pattern of the Mn-cluster need to be elucidated. The new high-resolution PSII crystal structure from Umena, Kawakami, Shen, and Kamiya is an excellent basis to make progress in solving this problem. Following our previous work on oxidation and protonation states of the Mn-cluster, in this work, quantum chemical/electrostatic calculations were performed in order to estimate the pKa of different protons of relevant groups and atoms of the Mn-cluster such as W2, O4, O5 and His337. In broad agreement with previous experimental and theoretical work, our data suggest that W2 and His337 are likely to be in hydroxyl and neutral form, respectively, O5 and O4 to be unprotonated. This article is part of a special issue entitled: photosynthesis research for sustainability: keys to produce clean energy.
Collapse
|
7
|
Robertazzi A, Galstyan A, Knapp EW. PSII manganese cluster: protonation of W2, O5, O4 and His337 in the S1 state explored by combined quantum chemical and electrostatic energy computations. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2014; 1837:1316-21. [PMID: 24721390 DOI: 10.1016/j.bbabio.2014.03.018] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2013] [Revised: 02/17/2014] [Accepted: 03/29/2014] [Indexed: 10/25/2022]
Abstract
Photosystem II (PSII) is a membrane-bound protein complex that oxidizes water to produce energized protons, which are used to built up a proton gradient across the thylakoidal membrane in the leafs of plants. This light-driven reaction is catalyzed by withdrawing electrons from the Mn₄CaO₅-cluster (Mn-cluster) in four discrete oxidation steps [S₁-(S₄/S₀)] characterized in the Kok-cycle. In order to understand in detail the proton release events and the subsequent translocation of such energized protons, the protonation pattern of the Mn-cluster need to be elucidated. The new high-resolution PSII crystal structure from Umena, Kawakami, Shen, and Kamiya is an excellent basis to make progress in solving this problem. Following our previous work on oxidation and protonation states of the Mn-cluster, in this work, quantum chemical/electrostatic calculations were performed in order to estimate the pKa of different protons of relevant groups and atoms of the Mn-cluster such as W2, O4, O5 and His337. In broad agreement with previous experimental and theoretical work, our data suggest that W2 and His337 are likely to be in hydroxyl and neutral form, respectively, O5 and O4 to be unprotonated. This article is part of a Special Issue entitled: Photosynthesis Research for Sustainability: Keys to Produce Clean Energy.
Collapse
Affiliation(s)
- Arturo Robertazzi
- Department of Biology, Chemistry and Pharmacy, Institute of Chemistry and Biochemistry, Freie Universität Berlin, Fabeckstr. 36a, D-14195 Berlin, Germany
| | - Artur Galstyan
- Department of Biology, Chemistry and Pharmacy, Institute of Chemistry and Biochemistry, Freie Universität Berlin, Fabeckstr. 36a, D-14195 Berlin, Germany
| | - Ernst Walter Knapp
- Department of Biology, Chemistry and Pharmacy, Institute of Chemistry and Biochemistry, Freie Universität Berlin, Fabeckstr. 36a, D-14195 Berlin, Germany.
| |
Collapse
|
8
|
Gonzalez PJ, Rivas MG, Mota CS, Brondino CD, Moura I, Moura JJ. Periplasmic nitrate reductases and formate dehydrogenases: Biological control of the chemical properties of Mo and W for fine tuning of reactivity, substrate specificity and metabolic role. Coord Chem Rev 2013. [DOI: 10.1016/j.ccr.2012.05.020] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
|
9
|
Galstyan A, Robertazzi A, Knapp EW. Oxygen-Evolving Mn Cluster in Photosystem II: The Protonation Pattern and Oxidation State in the High-Resolution Crystal Structure. J Am Chem Soc 2012; 134:7442-9. [DOI: 10.1021/ja300254n] [Citation(s) in RCA: 141] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Artur Galstyan
- Department of Biology,
Chemistry and Pharmacy, Institute
of Chemistry and Biochemistry, Freie Universität Berlin, Fabeckstrasse 36a, D-14195 Berlin, Germany
| | - Arturo Robertazzi
- Department of Biology,
Chemistry and Pharmacy, Institute
of Chemistry and Biochemistry, Freie Universität Berlin, Fabeckstrasse 36a, D-14195 Berlin, Germany
| | - Ernst Walter Knapp
- Department of Biology,
Chemistry and Pharmacy, Institute
of Chemistry and Biochemistry, Freie Universität Berlin, Fabeckstrasse 36a, D-14195 Berlin, Germany
| |
Collapse
|
10
|
Light-driven oxygen production from superoxide by Mn-binding bacterial reaction centers. Proc Natl Acad Sci U S A 2012; 109:2314-8. [PMID: 22308385 DOI: 10.1073/pnas.1115364109] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
One of the outstanding questions concerning the early Earth is how ancient phototrophs made the evolutionary transition from anoxygenic to oxygenic photosynthesis, which resulted in a substantial increase in the amount of oxygen in the atmosphere. We have previously demonstrated that reaction centers from anoxygenic photosynthetic bacteria can be modified to bind a redox-active Mn cofactor, thus gaining a key functional feature of photosystem II, which contains the site for water oxidation in cyanobacteria, algae, and plants [Thielges M, et al. (2005) Biochemistry 44:7389-7394]. In this paper, the Mn-binding reaction centers are shown to have a light-driven enzymatic function; namely, the ability to convert superoxide into molecular oxygen. This activity has a relatively high efficiency with a k(cat) of approximately 1 s(-1) that is significantly larger than typically observed for designed enzymes, and a K(m) of 35-40 μM that is comparable to the value of 50 μM for Mn-superoxide dismutase, which catalyzes a similar reaction. Unlike wild-type reaction centers, the highly oxidizing reaction centers are not stable in the light unless they have a bound Mn. The stability and enzymatic ability of this type of Mn-binding reaction centers would have provided primitive phototrophs with an environmental advantage before the evolution of organisms with a more complex Mn(4)Ca cluster needed to perform the multielectron reactions required to oxidize water.
Collapse
|
11
|
Faunce T. Towards Global Artificial Photosynthesis (Global Solar Fuels): Energy, Nanochemistry, and Governance. Aust J Chem 2012. [DOI: 10.1071/ch12193] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
|
12
|
Pereira NAM, Fonseca SM, Serra AC, Pinho e Melo TMVD, Burrows HD. [8π+2π] Cycloaddition of meso-Tetra- and 5,15-Diarylporphyrins: Synthesis and Photophysical Characterization of Stable Chlorins and Bacteriochlorins. European J Org Chem 2011. [DOI: 10.1002/ejoc.201100465] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
|
13
|
Magalon A, Fedor JG, Walburger A, Weiner JH. Molybdenum enzymes in bacteria and their maturation. Coord Chem Rev 2011. [DOI: 10.1016/j.ccr.2010.12.031] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
|
14
|
Kálmán L, Williams JC, Allen JP. Energetics for Oxidation of a Bound Manganese Cofactor in Modified Bacterial Reaction Centers. Biochemistry 2011; 50:3310-20. [PMID: 21375274 DOI: 10.1021/bi1017478] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- L. Kálmán
- Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604, United States
| | - J. C. Williams
- Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604, United States
| | - J. P. Allen
- Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604, United States
| |
Collapse
|
15
|
Rea G, Lambreva M, Polticelli F, Bertalan I, Antonacci A, Pastorelli S, Damasso M, Johanningmeier U, Giardi MT. Directed evolution and in silico analysis of reaction centre proteins reveal molecular signatures of photosynthesis adaptation to radiation pressure. PLoS One 2011; 6:e16216. [PMID: 21249156 PMCID: PMC3020971 DOI: 10.1371/journal.pone.0016216] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2010] [Accepted: 12/15/2010] [Indexed: 11/18/2022] Open
Abstract
Evolutionary mechanisms adopted by the photosynthetic apparatus to modifications in the Earth's atmosphere on a geological time-scale remain a focus of intense research. The photosynthetic machinery has had to cope with continuously changing environmental conditions and particularly with the complex ionizing radiation emitted by solar flares. The photosynthetic D1 protein, being the site of electron tunneling-mediated charge separation and solar energy transduction, is a hot spot for the generation of radiation-induced radical injuries. We explored the possibility to produce D1 variants tolerant to ionizing radiation in Chlamydomonas reinhardtii and clarified the effect of radiation-induced oxidative damage on the photosynthetic proteins evolution. In vitro directed evolution strategies targeted at the D1 protein were adopted to create libraries of chlamydomonas random mutants, subsequently selected by exposures to radical-generating proton or neutron sources. The common trend observed in the D1 aminoacidic substitutions was the replacement of less polar by more polar amino acids. The applied selection pressure forced replacement of residues more sensitive to oxidative damage with less sensitive ones, suggesting that ionizing radiation may have been one of the driving forces in the evolution of the eukaryotic photosynthetic apparatus. A set of the identified aminoacidic substitutions, close to the secondary plastoquinone binding niche and oxygen evolving complex, were introduced by site-directed mutagenesis in un-transformed strains, and their sensitivity to free radicals attack analyzed. Mutants displayed reduced electron transport efficiency in physiological conditions, and increased photosynthetic performance stability and oxygen evolution capacity in stressful high-light conditions. Finally, comparative in silico analyses of D1 aminoacidic sequences of organisms differently located in the evolution chain, revealed a higher ratio of residues more sensitive to oxidative damage in the eukaryotic/cyanobacterial proteins compared to their bacterial orthologs. These results led us to hypothesize an archaean atmosphere less challenging in terms of ionizing radiation than the present one.
Collapse
Affiliation(s)
- Giuseppina Rea
- Institute of Crystallography, National Research Council, Monterotondo, Italy.
| | | | | | | | | | | | | | | | | |
Collapse
|
16
|
Pereira NAM, Serra AC, Pinho e Melo TMVD. Novel Approach to Chlorins and Bacteriochlorins: [8π+2π] Cycloaddition of Diazafulvenium Methides with Porphyrins. European J Org Chem 2010. [DOI: 10.1002/ejoc.201001157] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
|