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Zabelin AA, Shkuropatov AY. Pigment-modified reaction centers of Chloroflexus aurantiacus: chemical exchange of bacteriopheophytins with plant-type pheophytins. PHOTOSYNTHESIS RESEARCH 2021; 149:313-328. [PMID: 34138452 DOI: 10.1007/s11120-021-00855-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Accepted: 06/06/2021] [Indexed: 06/12/2023]
Abstract
The pigment composition of isolated reaction centers (RCs) of the green filamentous bacterium Chloroflexus (Cfl.) aurantiacus was changed by chemical exchange of native bacteriopheophytin a (BPheo) molecules with externally added pheophytin a (Pheo) or [3-acetyl]-Pheo upon incubation of RC/pheophytin mixtures at room temperature and 45 °C. The modified RCs were characterized by Vis/NIR absorption spectroscopy, and the effect of pigment exchange on RC photochemical activity was assessed by measuring the photoaccumulation of the reduced pigment at the binding site HA. It is shown that both pheophytins can be exchanged into the HA site instead of BPheo by incubation at room temperature. While the newly introduced Pheo molecule is not active in electron transfer, the [3-acetyl]-Pheo molecule is able to replace functionally the photoreducible HA BPheo molecule with the formation of the [3-acetyl]-Pheo- radical anion instead of the BPheo-. After incubation at 45 °C, the majority (~ 90%) of HA BPheo molecules is replaced by both Pheo and [3-acetyl]-Pheo. Only a partial replacement of inactive BPheo molecules with pheophytins is observed even when the incubation temperature is raised to 50 °C. The results are discussed in terms of (i) differences in the accessibility of BPheo binding sites for extraneous pigments depending on structural constraints and incubation temperature and (ii) the effect of the reduction potential of pigments introduced into the HA site on the energetics of the charge separation process. The possible implication of Pheo-exchanged preparations for studying early electron-transfer events in Cfl. aurantiacus RCs is considered.
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Affiliation(s)
- Alexey A Zabelin
- Federal Research Center "Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences", Institute of Basic Biological Problems of the Russian Academy of Sciences, 142290, Pushchino, Moscow Region, Russian Federation
| | - Anatoly Ya Shkuropatov
- Federal Research Center "Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences", Institute of Basic Biological Problems of the Russian Academy of Sciences, 142290, Pushchino, Moscow Region, Russian Federation.
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Sipka G, Magyar M, Mezzetti A, Akhtar P, Zhu Q, Xiao Y, Han G, Santabarbara S, Shen JR, Lambrev PH, Garab G. Light-adapted charge-separated state of photosystem II: structural and functional dynamics of the closed reaction center. THE PLANT CELL 2021; 33:1286-1302. [PMID: 33793891 PMCID: PMC8225241 DOI: 10.1093/plcell/koab008] [Citation(s) in RCA: 55] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2020] [Accepted: 12/13/2020] [Indexed: 05/04/2023]
Abstract
Photosystem II (PSII) uses solar energy to oxidize water and delivers electrons for life on Earth. The photochemical reaction center of PSII is known to possess two stationary states. In the open state (PSIIO), the absorption of a single photon triggers electron-transfer steps, which convert PSII into the charge-separated closed state (PSIIC). Here, by using steady-state and time-resolved spectroscopic techniques on Spinacia oleracea and Thermosynechococcus vulcanus preparations, we show that additional illumination gradually transforms PSIIC into a light-adapted charge-separated state (PSIIL). The PSIIC-to-PSIIL transition, observed at all temperatures between 80 and 308 K, is responsible for a large part of the variable chlorophyll-a fluorescence (Fv) and is associated with subtle, dark-reversible reorganizations in the core complexes, protein conformational changes at noncryogenic temperatures, and marked variations in the rates of photochemical and photophysical reactions. The build-up of PSIIL requires a series of light-induced events generating rapidly recombining primary radical pairs, spaced by sufficient waiting times between these events-pointing to the roles of local electric-field transients and dielectric relaxation processes. We show that the maximum fluorescence level, Fm, is associated with PSIIL rather than with PSIIC, and thus the Fv/Fm parameter cannot be equated with the quantum efficiency of PSII photochemistry. Our findings resolve the controversies and explain the peculiar features of chlorophyll-a fluorescence kinetics, a tool to monitor the functional activity and the structural-functional plasticity of PSII in different wild-types and mutant organisms and under stress conditions.
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Affiliation(s)
- G�bor Sipka
- Institute of Plant Biology, Biological Research Centre, Szeged, Hungary
| | - Melinda Magyar
- Institute of Plant Biology, Biological Research Centre, Szeged, Hungary
| | - Alberto Mezzetti
- Universit� Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC) 91191 Gif-sur-Yvette, France
- Laboratoire de R�activit� de Surface UMR 7197, Sorbonne University, Paris, France
| | - Parveen Akhtar
- Institute of Plant Biology, Biological Research Centre, Szeged, Hungary
- ELI-ALPS, ELI-HU Nonprofit Ltd., Szeged, Hungary
| | - Qingjun Zhu
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing, China
| | - Yanan Xiao
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing, China
| | - Guangye Han
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing, China
| | - Stefano Santabarbara
- Photosynthetic Research Unit, Institute of Biophysics, National Research Council of Italy, Milano, Italy
| | - Jian-Ren Shen
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing, China
- Research Institute for Interdisciplinary Science, and Graduate School of Natural Science and Technology, Okayama University, Okayama, Japan
| | - Petar H Lambrev
- Institute of Plant Biology, Biological Research Centre, Szeged, Hungary
- Author for correspondence: (G.G.), (P.H.L.)
| | - Győző Garab
- Institute of Plant Biology, Biological Research Centre, Szeged, Hungary
- Faculty of Science, University of Ostrava, Ostrava, Czech Republic
- Author for correspondence: (G.G.), (P.H.L.)
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Oppelt KT, Wöß E, Stiftinger M, Schöfberger W, Buchberger W, Knör G. Photocatalytic reduction of artificial and natural nucleotide co-factors with a chlorophyll-like tin-dihydroporphyrin sensitizer. Inorg Chem 2013; 52:11910-22. [PMID: 24073596 PMCID: PMC3805326 DOI: 10.1021/ic401611v] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
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An
efficient photocatalytic two-electron reduction and protonation
of nicotine amide adenine dinucleotide (NAD+), as well
as the synthetic nucleotide co-factor analogue N-benzyl-3-carbamoyl-pyridinium
(BNAD+), powered by photons in the long-wavelength region
of visible light (λirr > 610 nm), is demonstrated
for the first time. This functional artificial photosynthetic counterpart
of the complete energy-trapping and solar-to-fuel conversion primary
processes occurring in natural photosystem I (PS I) is achieved with
a robust water-soluble tin(IV) complex of meso-tetrakis(N-methylpyridinium)-chlorin acting as the light-harvesting
sensitizer (threshold wavelength of λthr = 660 nm).
In buffered aqueous solution, this chlorophyll-like compound photocatalytically
recycles a rhodium hydride complex of the type [Cp*Rh(bpy)H]+, which is able to mediate regioselective hydride transfer processes.
Different one- and two-electron donors are tested for the reductive
quenching of the irradiated tin complex to initiate the secondary
dark reactions leading to nucleotide co-factor reduction. Very promising
conversion efficiencies, quantum yields, and excellent photosensitizer
stabilities are observed. As an example of a catalytic dark reaction
utilizing the reduction equivalents of accumulated NADH, an enzymatic
process for the selective transformation of aldehydes with alcohol
dehydrogenase (ADH) coupled to the primary photoreactions of the system
is also demonstrated. A tentative reaction mechanism for the transfer
of two electrons and one proton from the reductively quenched tin
chlorin sensitizer to the rhodium co-catalyst, acting as a reversible
hydride carrier, is proposed. An efficient photocatalytic
system for the two-electron
reduction of nucleotide co-factors has been characterized. For the
first time it could be demonstrated in an abiotic system that the
long-wavelength region of the visible spectrum (> 610 nm) can be
exploited
to power the accumulation of NADH. The artificial photosynthetic reaction
sequence, described here in detail, can be regarded as the first true
functional model system for the overall light reactions occurring
in natural photosystem I.
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Affiliation(s)
- Kerstin T Oppelt
- Institute of Inorganic Chemistry, and ‡Institute of Analytical Chemistry, Johannes Kepler University Linz (JKU) , A-4040 Linz, Austria
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Shkuropatov AY, Khatypov RA, Volshchukova TS, Shkuropatova VA, Owens TG, Shuvalov VA. Spectral and photochemical properties of borohydride-treated D1-D2-cytochrome b-559 complex of photosystem II. FEBS Lett 1997; 420:171-4. [PMID: 9459304 DOI: 10.1016/s0014-5793(97)01512-3] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The D1-D2-cytochrome b-559 reaction center complex of photosystem II with an altered pigment composition was prepared from the original complex by treatment with sodium borohydride (BH4-). The absorption spectra of the modified and original complexes were compared to each other and to the spectra of purified chlorophyll a and pheophytin a (Pheo a) treated with BH4- in methanolic solution. The results of these comparisons are consistent with the presence in the modified complex of an irreversibly reduced Pheo a molecule, most likely 13(1)-deoxo-13(1)-hydroxy-Pheo a, replacing one of the two native Pheo a molecules present in the original complex. Similar to the original preparation, the modified complex was capable of a steady-state photoaccumulation of Pheo- and P680+. It is concluded that the pheophytin a molecule which undergoes borohydride reduction is not involved in the primary charge separation and seems to represent a previously postulated photochemically inactive Pheo a molecule. The Qy and Qx transitions of this molecule were determined to be located at 5 degrees C at 679.5-680 nm and 542 nm, respectively.
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Affiliation(s)
- A Y Shkuropatov
- Institute of Soil Science and Photosynthesis, Russian Academy of Sciences, Pushchino, Moscow Region, Russian Federation.
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Pico- and nanosecond fluorescence kinetics of Photosystem II reaction centre and its complex with CP47 antenna. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1994. [DOI: 10.1016/0005-2728(94)90152-x] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Affiliation(s)
- P Horton
- Robert Hill Institute, Department of Molecular Biology & Biotechnology, University of Sheffield, Firth Court, PO Box 594, S10 2UH, Sheffield, UK
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De Las Rivas J, Crystall B, Booth PJ, Durrant JR, Ozer S, Porter G, Klug DR, Barber J. Long-lived primary radical pair state detected by time-resolved fluorescence and absorption spectroscopy in an isolated Photosystem two core. PHOTOSYNTHESIS RESEARCH 1992; 34:419-431. [PMID: 24408837 DOI: 10.1007/bf00029816] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/1992] [Accepted: 06/08/1992] [Indexed: 06/03/2023]
Abstract
A Photosystem two (PS II) core preparation containing the chlorophyll a binding proteins CP 47, CP 43, D1 and D2, and the non-chlorophyll binding cytochrome-b559 and 33 kDA polypeptides, has been isolated from PS II-enriched membranes of peas using the non-ionic detergent heptylthioglucopyranoside and elevated ionic strengths. The primary radical pair state, P680(+)Pheo(-), was studied by time-resolved absorption and fluorescence spectroscopy, under conditions where quinone reduction and water-splitting activities were inhibited. Charge recombination of the primary radical pair in PS II cores was found to have lifetimes of 17.5 ns measured by fluorescence and 21 ns measured by transient decay kinetics under anaerobic conditions. Transient absorption spectroscopy demonstrated that the activity of the particles, based on primary radical pair formation, was in excess of 70% (depending on the choice of kinetic model), while time-resolved fluorescence spectroscopy indicated that the particles were 91% active. These estimates of activity were further supported by steady-state measurements which quantified the amount of photoreducible pheophytin. It is concluded that the PS II core preparation we have isolated is ideal for studying primary radical pair formation and recombination as demonstrated by the correlation of our absorption and fluorescence transient data, which is the first of its kind to be reported in the literature for isolated PS II core complexes from higher plants.
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Gray KA, Wachtveitl J, Oesterhelt D. Photochemical trapping of a bacteriopheophytin anion in site-specific reaction-center mutants from the photosynthetic bacterium Rhodobacter sphaeroides. EUROPEAN JOURNAL OF BIOCHEMISTRY 1992; 207:723-31. [PMID: 1633823 DOI: 10.1111/j.1432-1033.1992.tb17102.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The mutant YY in the reaction center of Rhodobacter sphaeroides, in which Phe181 on the L chain has been replaced by Tyr, and the double mutant FY, with Tyr210 on the M chain replaced by Phe and Phe181 on the L chain replaced by Tyr, have been constructed by site-directed mutagenesis. The studies described here were performed to complement a previous mutational analysis of mutant FF with Tyr210 replaced by Phe. Both new strains grow photoheterotrophically. The optical absorption spectra of reaction centers isolated from these mutants have band shifts attributable to the monomer bacteriochlorophylls in the vicinity of the substitutions. Photochemical trapping of the bacteriopheophytin anion (I-) indicates that the bacteriopheophytin on the B branch is reduced to a much greater extent in FF and FY as compared to YY and wild-type YF. Low temperature (77 K) absorption spectra clearly show that in the wild-type (YF) and YY reaction centers only the 545-nm-absorbing bacteriopheophytin is reduced while in the FF and FY reaction centers both the 535-nm and 545-nm-absorbing bacteriopheophytins are reduced. A simple kinetic analysis is used to explain these results. This analysis suggests that, in order for the observed trapping results to occur, a decrease in the 'cycling' time must take place, that is changes in the rate(s) of charge recombination must accompany the already known decrease in the forward electron transfer rate.
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Affiliation(s)
- K A Gray
- Department of Membrane Biochemistry, Max-Planck-Institut für Biochemie, Martinsried, Federal Republic of Germany
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Damage to functional components and partial degradation of Photosystem II reaction center proteins upon chloroplast exposure to ultraviolet-B radiation. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1992. [DOI: 10.1016/0167-4838(92)90487-x] [Citation(s) in RCA: 140] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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