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Journal of Photochemistry and... Nov 2015Both photosystem I and photosystem II are considerably similar in molecular architecture but they operate at very different electrochemical potentials. The origin of the... (Review)
Review
Both photosystem I and photosystem II are considerably similar in molecular architecture but they operate at very different electrochemical potentials. The origin of the different redox properties of these RCs is not yet clear. In recent years, insight was gained into the electronic structure of photosynthetic cofactors through the application of photochemically induced dynamic nuclear polarization (photo-CIDNP) with magic-angle spinning NMR (MAS NMR). Non-Boltzmann populated nuclear spin states of the radical pair lead to strongly enhanced signal intensities that allow one to observe the solid-state photo-CIDNP effect from both photosystem I and II from isolated reaction center of spinach (Spinacia oleracea) and duckweed (Spirodela oligorrhiza) and from the intact cells of the cyanobacterium Synechocystis by (13)C and (15)N MAS NMR. This review provides an overview on the photo-CIDNP MAS NMR studies performed on PSI and PSII that provide important ingredients toward reconstruction of the electronic structures of the donors in PSI and PSII.
Topics: Electron Transport; Magnetic Resonance Spectroscopy; Oxygen; Photosynthesis; Photosystem I Protein Complex; Photosystem II Protein Complex
PubMed: 26282679
DOI: 10.1016/j.jphotobiol.2015.08.001 -
Photosynthesis Research 2008A short overview is given on the discovery of the chlorophyll d-dominated cyanobacterium Acaryochloris marina and the minor pigments that function as key components... (Review)
Review
A short overview is given on the discovery of the chlorophyll d-dominated cyanobacterium Acaryochloris marina and the minor pigments that function as key components therein. In photosystem I, chlorophyll d', chlorophyll a, and phylloquinone function as the primary electron donor, the primary electron acceptor and the secondary electron acceptor, respectively. In photosystem II, pheophytin a serves as the primary electron acceptor. The oxidation potential of chlorophyll d was higher than that of chlorophyll a in vitro, while the oxidation potential of P740 was almost the same as that of P700. These results help us to broaden our view on the questions about the unique photosystems in Acaryochloris marina.
Topics: Chlorophyll; Cyanobacteria; Photosynthesis; Photosynthetic Reaction Center Complex Proteins
PubMed: 18985431
DOI: 10.1007/s11120-008-9383-1 -
Current Opinion in Plant Biology Jun 2015In the thylakoid membrane, the two photosystems act in series to promote linear electron flow, with the concomitant production of ATP and reducing equivalents such as... (Review)
Review
In the thylakoid membrane, the two photosystems act in series to promote linear electron flow, with the concomitant production of ATP and reducing equivalents such as NADPH. Photosystem I, which is preferentially activated in far-red light, also energizes cyclic electron flow which generates only ATP. Thus, changes in light quality and cellular metabolic demand require a rapid regulation of the activity of the two photosystems. At low light intensities, this is mediated by state transitions. They allow the dynamic allocation of light harvesting antennae to the two photosystems, regulated through protein phosphorylation by a kinase and phosphatase pair that respond to the redox state of the electron transfer chain. Phosphorylation of the antennae leads to remodeling of the photosynthetic complexes.
Topics: Chlamydomonas; Light; Oxidation-Reduction; Phosphorylation; Photosystem I Protein Complex; Photosystem II Protein Complex; Plants; Thylakoids
PubMed: 26002067
DOI: 10.1016/j.pbi.2015.04.009 -
FEMS Microbiology Letters Feb 2011Current molecular analyses suggest that initial steps of the biogenesis of cyanobacterial photosystems progress in a membrane subfraction representing a biosynthetic... (Review)
Review
Current molecular analyses suggest that initial steps of the biogenesis of cyanobacterial photosystems progress in a membrane subfraction representing a biosynthetic center with contact to both plasma and thylakoid membranes. This special membrane fraction is defined by the presence of the photosystem II assembly factor PratA. The proposed model suggests that both biogenesis of protein complexes and insertion of chlorophyll molecules into the photosystems occur in this intermediate membrane system.
Topics: Cell Membrane; Chlorophyll; Cyanobacteria; Models, Biological; Periplasmic Proteins; Photosynthetic Reaction Center Complex Proteins; Synechocystis; Thylakoids
PubMed: 20831593
DOI: 10.1111/j.1574-6968.2010.02096.x -
Scientific Reports Oct 2017In oxygenic photosynthesis the initial photochemical processes are carried out by photosystem I (PSI) and II (PSII). Although subunit composition varies between...
In oxygenic photosynthesis the initial photochemical processes are carried out by photosystem I (PSI) and II (PSII). Although subunit composition varies between cyanobacterial and plastid photosystems, the core structures of PSI and PSII are conserved throughout photosynthetic eukaryotes. So far, the photosynthetic complexes have been characterised in only a small number of organisms. We performed in silico and biochemical studies to explore the organization and evolution of the photosynthetic apparatus in the chromerids Chromera velia and Vitrella brassicaformis, autotrophic relatives of apicomplexans. We catalogued the presence and location of genes coding for conserved subunits of the photosystems as well as cytochrome bf and ATP synthase in chromerids and other phototrophs and performed a phylogenetic analysis. We then characterised the photosynthetic complexes of Chromera and Vitrella using 2D gels combined with mass-spectrometry and further analysed the purified Chromera PSI. Our data suggest that the photosynthetic apparatus of chromerids underwent unique structural changes. Both photosystems (as well as cytochrome bf and ATP synthase) lost several canonical subunits, while PSI gained one superoxide dismutase (Vitrella) or two superoxide dismutases and several unknown proteins (Chromera) as new regular subunits. We discuss these results in light of the extraordinarily efficient photosynthetic processes described in Chromera.
Topics: Alveolata; Evolution, Molecular; Gene Deletion; Mass Spectrometry; Photosynthesis; Photosystem I Protein Complex; Phylogeny; Superoxide Dismutase; Thylakoids
PubMed: 29038514
DOI: 10.1038/s41598-017-13575-x -
Nature Jun 2004Photosynthesis provides at least two routes through which light energy can be used to generate a proton gradient across the thylakoid membrane of chloroplasts, which is...
Photosynthesis provides at least two routes through which light energy can be used to generate a proton gradient across the thylakoid membrane of chloroplasts, which is subsequently used to synthesize ATP. In the first route, electrons released from water in photosystem II (PSII) are eventually transferred to NADP+ by way of photosystem I (PSI). This linear electron flow is driven by two photochemical reactions that function in series. The cytochrome b6f complex mediates electron transport between the two photosystems and generates the proton gradient (DeltapH). In the second route, driven solely by PSI, electrons can be recycled from either reduced ferredoxin or NADPH to plastoquinone, and subsequently to the cytochrome b6f complex. Such cyclic flow generates DeltapH and thus ATP without the accumulation of reduced species. Whereas linear flow from water to NADP+ is commonly used to explain the function of the light-dependent reactions of photosynthesis, the role of cyclic flow is less clear. In higher plants cyclic flow consists of two partially redundant pathways. Here we have constructed mutants in Arabidopsis thaliana in which both PSI cyclic pathways are impaired, and present evidence that cyclic flow is essential for efficient photosynthesis.
Topics: Adenosine Triphosphate; Arabidopsis; Chloroplasts; Electron Transport; Ferricyanides; Genes, Plant; Hydrogen-Ion Concentration; Mutation; NADP; Oxygen; Phenotype; Photosynthesis; Photosystem I Protein Complex; Plastoquinone; Proton-Motive Force
PubMed: 15175756
DOI: 10.1038/nature02598 -
The Journal of Physical Chemistry... Apr 2016We have compared picosecond fluorescence decay kinetics for stacked and unstacked photosystem II membranes in order to evaluate the efficiency of excitation energy...
We have compared picosecond fluorescence decay kinetics for stacked and unstacked photosystem II membranes in order to evaluate the efficiency of excitation energy transfer between the neighboring layers. The measured kinetics were analyzed in terms of a recently developed fluctuating antenna model that provides information about the dimensionality of the studied system. Independently of the stacking state, all preparations exhibited virtually the same value of the apparent dimensionality, d = 1.6. Thus, we conclude that membrane stacking does not affect the efficiency of the delivery of excitation energy toward the reaction centers but ensures a more compact organization of the thylakoid membranes within the chloroplast and separation of photosystems I and II.
Topics: Energy Transfer; Models, Molecular; Photosystem II Protein Complex; Spinacia oleracea; Thylakoids
PubMed: 27014831
DOI: 10.1021/acs.jpclett.6b00474 -
Frontiers in Plant Science 2018Plant-type ferredoxins in Arabidopsis transfer electrons from the photosystem I to multiple redox-driven enzymes involved in the assimilation of carbon, nitrogen, and...
Plant-type ferredoxins in Arabidopsis transfer electrons from the photosystem I to multiple redox-driven enzymes involved in the assimilation of carbon, nitrogen, and sulfur. Leaf-type ferredoxins also modulate the switch between the linear and cyclic electron routes of the photosystems. Recently, two novel ferredoxin homologs with extra C-termini were identified in the Arabidopsis genome (AtFdC1, AT4G14890; AtFdC2, AT1G32550). FdC1 was considered as an alternative electron acceptor of PSI under extreme ferredoxin-deficient conditions. Here, we showed that FdC1 could interact with some, but not all, electron acceptors of leaf-type Fds, including the ferredoxin-thioredoxin reductase (FTR), sulfite reductase (SiR), and nitrite reductase (NiR). Photoreduction assay on cytochrome and enzyme assays confirmed its capability to receive electrons from PSI and donate electrons to the Fd-dependent SiR and NiR but not to the ferredoxin-NADP oxidoreductase (FNR). Hence, FdC1 and leaf-type Fds may play differential roles by channeling electrons from photosystem I to different downstream electron acceptors in photosynthetic tissues. In addition, the median redox potential of FdC1 may allow it to receive electrons from FNR in non-photosynthetic plastids.
PubMed: 29670639
DOI: 10.3389/fpls.2018.00410 -
ELife Jan 2013Oxygenic photosynthesis supports virtually all life forms on earth. Light energy is converted by two photosystems-photosystem I (PSI) and photosystem II (PSII)....
Oxygenic photosynthesis supports virtually all life forms on earth. Light energy is converted by two photosystems-photosystem I (PSI) and photosystem II (PSII). Globally, nearly 50% of photosynthesis takes place in the Ocean, where single cell cyanobacteria and algae reside together with their viruses. An operon encoding PSI was identified in cyanobacterial marine viruses. We generated a PSI that mimics the salient features of the viral complex, named PSI(PsaJF). PSI(PsaJF) is promiscuous for its electron donors and can accept electrons from respiratory cytochromes. We solved the structure of PSI(PsaJF) and a monomeric PSI, with subunit composition similar to the viral PSI, providing for the first time a detailed description of the reaction center and antenna system from mesophilic cyanobacteria, including red chlorophylls and cofactors of the electron transport chain. Our finding extends the understanding of PSI structure, function and evolution and suggests a unique function for the viral PSI. DOI: http://dx.doi.org/10.7554/eLife.01496.001.
Topics: Chlorophyll; Crystallization; Electron Transport; Kinetics; Models, Molecular; Oxidation-Reduction; Photosynthesis; Photosystem I Protein Complex; Protein Conformation; Structure-Activity Relationship; Synechocystis
PubMed: 24473073
DOI: 10.7554/eLife.01496 -
Science (New York, N.Y.) Aug 2020Oxygenic photosynthesis is the main process that drives life on earth. It starts with the harvesting of solar photons that, after transformation into electronic... (Review)
Review
Oxygenic photosynthesis is the main process that drives life on earth. It starts with the harvesting of solar photons that, after transformation into electronic excitations, lead to charge separation in the reaction centers of photosystems I and II (PSI and PSII). These photosystems are large, modular pigment-protein complexes that work in series to fuel the formation of carbohydrates, concomitantly producing molecular oxygen. Recent advances in cryo-electron microscopy have enabled the determination of PSI and PSII structures in complex with light-harvesting components called "supercomplexes" from different organisms at near-atomic resolution. Here, we review the structural and spectroscopic aspects of PSI and PSII from plants and algae that directly relate to their light-harvesting properties, with special attention paid to the pathways and efficiency of excitation energy transfer and the regulatory aspects.
Topics: Algal Proteins; Chlorophyta; Cryoelectron Microscopy; Energy Transfer; Oxygen; Photons; Photosynthesis; Photosystem I Protein Complex; Photosystem II Protein Complex
PubMed: 32820091
DOI: 10.1126/science.aay2058