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Photosynthesis Research Oct 2019Biological water oxidation, performed by a single enzyme, photosystem II, is a central research topic not only in understanding the photosynthetic apparatus but also for... (Review)
Review
Biological water oxidation, performed by a single enzyme, photosystem II, is a central research topic not only in understanding the photosynthetic apparatus but also for the development of water splitting catalysts for technological applications. Great progress has been made in this endeavor following the report of a high-resolution X-ray crystallographic structure in 2011 resolving the cofactor site (Umena et al. in Nature 473:55-60, 2011), a tetra-manganese calcium complex. The electronic properties of the protein-bound water oxidizing MnOCa complex are crucial to understand its catalytic activity. These properties include: its redox state(s) which are tuned by the protein matrix, the distribution of the manganese valence and spin states and the complex interactions that exist between the four manganese ions. In this short review we describe how magnetic resonance techniques, particularly EPR, complemented by quantum chemical calculations, have played an important role in understanding the electronic structure of the cofactor. Together with isotope labeling, these techniques have also been instrumental in deciphering the binding of the two substrate water molecules to the cluster. These results are briefly described in the context of the history of biological water oxidation with special emphasis on recent work using time resolved X-ray diffraction with free electron lasers. It is shown that these data are instrumental for developing a model of the biological water oxidation cycle.
Topics: Bacterial Proteins; Crystallography, X-Ray; Cyanobacteria; Kinetics; Models, Biological; Models, Chemical; Models, Molecular; Oxidation-Reduction; Oxygen; Photosystem II Protein Complex; Protein Structure, Tertiary; Thermosynechococcus; Water
PubMed: 31187340
DOI: 10.1007/s11120-019-00648-3 -
Biochimica Et Biophysica Acta.... Apr 2020Photosynthesis is a fundamental biological process involving the conversion of solar energy into chemical energy. The initial photochemical and photophysical events of... (Comparative Study)
Comparative Study Review
Photosynthesis is a fundamental biological process involving the conversion of solar energy into chemical energy. The initial photochemical and photophysical events of photosynthesis are mediated by photosystem II (PSII) and photosystem I (PSI). Both PSII and PSI are multi-subunit supramolecular machineries composed of a core complex and a peripheral antenna system. The antenna system serves to capture light energy and transfer it to the core efficiently. Both PSII and PSI in the green lineage (plants and green algae) and PSI in red algae have an antenna system comprising a series of chlorophyll- and carotenoid-binding membrane proteins belonging to the light-harvesting complex (LHC) superfamily, including LHCII and LHCI. However, the antenna size and subunit composition vary considerably in the two photosystems from diverse organisms. On the basis of the plant and algal LHCII and LHCI structures that have been solved by X-ray crystallography and single-particle cryo-electron microscopy we review the detailed structural features and characteristic pigment properties of these LHCs in PSII and PSI. This article is part of a Special Issue entitled Light harvesting, edited by Dr. Roberta Croce.
Topics: Amino Acid Sequence; Apoproteins; Chlamydomonas reinhardtii; Chlorophyll; Light-Harvesting Protein Complexes; Models, Molecular; Photosystem I Protein Complex; Photosystem II Protein Complex; Protein Subunits; Rhodophyta
PubMed: 31229568
DOI: 10.1016/j.bbabio.2019.06.010 -
Scientific Reports Jun 2022Plant growth under spectrally-enriched low light conditions leads to adjustment in the relative abundance of the two photosystems in an acclimatory response known as...
Plant growth under spectrally-enriched low light conditions leads to adjustment in the relative abundance of the two photosystems in an acclimatory response known as photosystem stoichiometry adjustment. Adjustment of photosystem stoichiometry improves the quantum efficiency of photosynthesis but how this process perceives light quality changes and how photosystem amount is regulated remain largely unknown. By using a label-free quantitative mass spectrometry approach in Arabidopsis here we show that photosystem stoichiometry adjustment is primarily driven by the regulation of photosystem I content and that this forms the major thylakoid proteomic response under light quality. Using light and redox signaling mutants, we further show that the light quality-responsive accumulation of photosystem I gene transcripts and proteins requires phytochrome B photoreceptor but not plastoquinone redox signaling as previously suggested. In far-red light, the increased acceptor side limitation might deplete active photosystem I pool, further contributing to the adjustment of photosystem stoichiometry.
Topics: Arabidopsis; Arabidopsis Proteins; Light; Oxidation-Reduction; Photosynthesis; Photosystem I Protein Complex; Photosystem II Protein Complex; Proteomics; Thylakoids
PubMed: 35768472
DOI: 10.1038/s41598-022-14967-4 -
Trends in Plant Science Nov 2019One of the earliest events in the molecular evolution of photosynthesis is the structural and functional specialisation of type I (ferredoxin-reducing) and type II... (Review)
Review
One of the earliest events in the molecular evolution of photosynthesis is the structural and functional specialisation of type I (ferredoxin-reducing) and type II (quinone-reducing) reaction centres. In this opinion article we point out that the homodimeric type I reaction centre of heliobacteria has a calcium-binding site with striking structural similarities to the MnCaO cluster of photosystem II. These similarities indicate that most of the structural elements required to evolve water oxidation chemistry were present in the earliest reaction centres. We suggest that the divergence of type I and type II reaction centres was made possible by a drastic structural shift linked to a change in redox properties that coincided with or facilitated the origin of photosynthetic water oxidation.
Topics: Evolution, Molecular; Oxidation-Reduction; Oxygen; Photosynthesis; Photosystem II Protein Complex; Water
PubMed: 31351761
DOI: 10.1016/j.tplants.2019.06.016 -
Plant Physiology Apr 2021
Topics: Abelmoschus; Biological Transport; Chlamydomonas; Fruit; Heat-Shock Proteins; Heat-Shock Response; Solanum lycopersicum; Nitrogen; Phenotype; Phospholipases; Photosystem II Protein Complex; Plant Roots; Quercetin; Seeds
PubMed: 35237825
DOI: 10.1093/plphys/kiaa112 -
Photosynthesis Research Jun 2023Photosynthetic water oxidation by Photosystem II (PSII) is a fascinating process because it sustains life on Earth and serves as a blue print for scalable synthetic... (Review)
Review
Photosynthetic water oxidation by Photosystem II (PSII) is a fascinating process because it sustains life on Earth and serves as a blue print for scalable synthetic catalysts required for renewable energy applications. The biophysical, computational, and structural description of this process, which started more than 50 years ago, has made tremendous progress over the past two decades, with its high-resolution crystal structures being available not only of the dark-stable state of PSII, but of all the semi-stable reaction intermediates and even some transient states. Here, we summarize the current knowledge on PSII with emphasis on the basic principles that govern the conversion of light energy to chemical energy in PSII, as well as on the illustration of the molecular structures that enable these reactions. The important remaining questions regarding the mechanism of biological water oxidation are highlighted, and one possible pathway for this fundamental reaction is described at a molecular level.
Topics: Photosystem II Protein Complex; Solar Energy; Photosynthesis; Oxidation-Reduction; Water; Oxygen
PubMed: 36826741
DOI: 10.1007/s11120-022-00991-y -
Biophysical Reviews Aug 2022Certain microalgae species are capable of light-dependent hydrogen production under conditions of dark anaerobic incubation or nutrient deprivation. From the... (Review)
Review
Certain microalgae species are capable of light-dependent hydrogen production under conditions of dark anaerobic incubation or nutrient deprivation. From the biotechnological point of view, this phenomenon is a process of synthesizing the energy carrier H while consuming light energy. Here, we overview the functional connection between the photosynthetic machinery and light-dependent hydrogen production and assess the physiological significance of this process. We characterize events involved in PSII downregulation, as well as the relationship between PSII regulation mechanisms and hydrogen generation. We suggest that the light-dependent hydrogen production forms part and parcel of the sophisticated regulatory network ensuring adaptation of microalgae to such environmental stresses as anaerobiosis or nutrient deprivation.
PubMed: 36124275
DOI: 10.1007/s12551-022-00977-z -
The New Phytologist May 2022Paulinella represents the only known case of an independent primary plastid endosymbiosis, outside Archaeplastida, that occurred c. 120 (million years ago) Ma. These...
Paulinella represents the only known case of an independent primary plastid endosymbiosis, outside Archaeplastida, that occurred c. 120 (million years ago) Ma. These photoautotrophs grow very slowly in replete culture medium with a doubling time of 6-7 d at optimal low light, and are highly sensitive to photodamage under moderate light levels. We used genomic and biophysical methods to investigate the extreme slow growth rate and light sensitivity of Paulinella, which are key to photosymbiont integration. All photosystem II (PSII) genes except psb28-2 and all cytochrome b f complex genes except petM and petL are present in Paulinella micropora KR01 (hereafter, KR01). Biophysical measurements of the water oxidation complex, variable chlorophyll fluorescence, and photosynthesis-irradiance curves show no obvious evidence of PSII impairment. Analysis of photoacclimation under high-light suggests that although KR01 can perform charge separation, it lacks photoprotection mechanisms present in cyanobacteria. We hypothesize that Paulinella species are restricted to low light environments because they are deficient in mitigating the formation of reactive oxygen species formed within the photosystems under peak solar intensities. The finding that many photoprotection genes have been lost or transferred to the host-genome during endosymbiont genome reduction, and may lack light-regulation, is consistent with this hypothesis.
Topics: Amoeba; Chromatophores; Light; Photosynthesis; Photosystem II Protein Complex; Phylogeny
PubMed: 35211975
DOI: 10.1111/nph.18052 -
Angewandte Chemie (International Ed. in... Apr 2022Photosystem-II uses sunlight to trigger charge separation and catalyze water oxidation. Intrinsic properties of chlorophyll a pigments define a natural "red limit" of...
Photosystem-II uses sunlight to trigger charge separation and catalyze water oxidation. Intrinsic properties of chlorophyll a pigments define a natural "red limit" of photosynthesis at ≈680 nm. Nevertheless, charge separation can be triggered with far-red photons up to 800 nm, without altering the nature of light-harvesting pigments. Here we identify the electronic origin of this remarkable phenomenon using quantum chemical and multiscale simulations on a native Photosystem-II model. We find that the reaction center is preorganized for charge separation in the far-red region by specific chlorophyll-pheophytin pairs, potentially bypassing the light-harvesting apparatus. Charge transfer can occur along two distinct pathways with one and the same pheophytin acceptor (Pheo ). The identity of the donor chlorophyll (Chl or P ) is wavelength-dependent and conformational dynamics broaden the sampling of the far-red region by the two charge-transfer states. The two pathways rationalize spectroscopic observations and underpin designed extensions of the photosynthetically active radiation limit.
Topics: Chlorophyll; Chlorophyll A; Electronics; Oxygen; Photosynthesis; Photosystem II Protein Complex
PubMed: 35142017
DOI: 10.1002/anie.202200356 -
Nature Communications Mar 2022Cyclophilins, or immunophilins, are proteins found in many organisms including bacteria, plants and humans. Most of them display peptidyl-prolyl cis-trans isomerase...
Cyclophilins, or immunophilins, are proteins found in many organisms including bacteria, plants and humans. Most of them display peptidyl-prolyl cis-trans isomerase activity, and play roles as chaperones or in signal transduction. Here, we show that cyclophilin anaCyp40 from the cyanobacterium Anabaena sp. PCC 7120 is enzymatically active, and seems to be involved in general stress responses and in assembly of photosynthetic complexes. The protein is associated with the thylakoid membrane and interacts with phycobilisome and photosystem components. Knockdown of anacyp40 leads to growth defects under high-salt and high-light conditions, and reduced energy transfer from phycobilisomes to photosystems. Elucidation of the anaCyp40 crystal structure at 1.2-Å resolution reveals an N-terminal helical domain with similarity to PsbQ components of plant photosystem II, and a C-terminal cyclophilin domain with a substrate-binding site. The anaCyp40 structure is distinct from that of other multi-domain cyclophilins (such as Arabidopsis thaliana Cyp38), and presents features that are absent in single-domain cyclophilins.
Topics: Cyanobacteria; Cyclophilins; Humans; Photosystem II Protein Complex; Phycobilisomes; Thylakoids
PubMed: 35354803
DOI: 10.1038/s41467-022-29211-w