Hydroxyl Radical Generation by Photosystem II

Pospı́šil, Pavel; Arató, András; Krieger‐Liszkay, Anja; Rutherford, A. William

doi:10.1021/bi036219i

Cited by 120 publications

(90 citation statements)

References 73 publications

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“…1 is not observed. The high-pO 2 effects in the X-ray data can be rationalized by Mn oxidation by ROS formed upon flash illumination (39)(40)(41)43) and/or dark oxidation of the S 0 and S 1 -state, the 2 lowpotential S-states (5). Either option is sufficient to model adequately the X-ray data.…”

Section: Discussionmentioning

confidence: 99%

Photosynthetic water oxidation at elevated dioxygen partial pressure monitored by time-resolved X-ray absorption measurements

Haumann

Grundmeier

Zaharieva

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

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The atmospheric dioxygen (O2) is produced at a tetramanganese complex bound to the proteins of photosystem II (PSII). To investigate product inhibition at elevated oxygen partial pressure (pO 2 ranging from 0.2 to 16 bar), we monitored specifically the redox reactions of the Mn complex in its catalytic S-state cycle by rapid-scan and time-resolved X-ray absorption near-edge spectroscopy (XANES) at the Mn K-edge. By using a pressure cell for X-ray measurements after laser-flash excitation of PSII particles, we found a clear pO 2 influence on the redox reactions of the Mn complex, with a similar half-effect pressure as determined (2-3 bar). However, XANES spectra and the time courses of the X-ray fluorescence collected with microsecond resolution suggested that the O 2 evolution transition itself (S3fS0؉O2) was not affected. Additional (nonstandard) oxidation of the Mn complex at high pO 2 explains our experimental findings more readily. Our results suggest that photosynthesis at ambient conditions is not limited by product inhibition of the O 2 formation step. manganese complex ͉ photosystem II ͉ X-ray spectroscopy ͉ bioinorganic chemistry ͉ oxygen pressure I n oxygenic photosynthesis, plants, algae, and cyanobacteria facilitate the primary biomass formation by exploiting solar energy for driving the conversion of water (H 2 O) and carbon dioxide (CO 2 ) into carbohydrates (C n H 2n O n ). Dioxygen (O 2 ) is formed as product of the water oxidation chemistry of the photosystem II (PSII) protein complex (1-5). Photosynthetic CO 2 fixation and O 2 formation have shaped the Earth's atmosphere (6) by (i) lowering the CO 2 level to Ͻ0.04% and (ii) creation of a maximal O 2 concentration of 35% (7), Ϸ300 million years before the present and a current level of Ϸ20%.In photosynthetic organisms, the low level of atmospheric CO 2 can limit photosynthesis, related to the activity of CO 2 -fixing ribulose bisphosphate carboxylase (8, 9). It is less clear whether water oxidation by PSII is directly affected by the concentration of O 2 , the immediate product of light-driven water splitting. This question was only recently addressed experimentally by Clausen and Junge (10). They exposed PSII from cyanobacteria to oxygen partial pressures (pO 2 ) ranging from 0.2 to 30 bar and, analyzing flash-induced near-UV absorption changes, discovered a pO 2 effect with a half-saturation pressure of only Ϸ2 bar (10). Subsequently, in measurements of delayed Chl fluorescence, together with Clausen and Junge we confirmed that also the donor side of the plant PSII in its native membrane environment is affected by elevated pO 2 (11). The surprisingly low halfpressure of only 2-3 bar was taken as an indication that the efficiency of the O 2 formation step could be reduced significantly by product inhibition. Such a limitation of the water oxidation chemistry may have imposed restraints on the evolution of oxygenic photosynthesis (10). Notably, the pO 2 inside of photosynthetic cells in microbial mats and bioreactors can be severalfold higher th...

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Section: Discussionmentioning

confidence: 99%

Photosynthetic water oxidation at elevated dioxygen partial pressure monitored by time-resolved X-ray absorption measurements

Haumann

Grundmeier

Zaharieva

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

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“…•− with the nonheme iron (14). In this reaction, a ferric-peroxo species is formed, the protonation of which produces a ferric-hydroperoxo species.…”

Section: •−mentioning

confidence: 99%

Amino acid oxidation of the D1 and D2 proteins by oxygen radicals during photoinhibition of Photosystem II

Kale

Hebert

Frankel

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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134

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The Photosystem II reaction center is vulnerable to photoinhibition. The D1 and D2 proteins, lying at the core of the photosystem, are susceptible to oxidative modification by reactive oxygen species that are formed by the photosystem during illumination. Using spin probes and EPR spectroscopy, we have determined that both O 2 . The identification of specific amino acid residues oxidized by reactive oxygen species provides insights into the mechanism of damage to the D1 and D2 proteins under light stress.photosynthesis | Photosystem II | reactive oxygen species | photo inhibition | mass spectrometry P hotosystem II (PSII) functions as a water-plastoquinone oxidoreductase (1, 2) and is a thylakoid membrane pigmentprotein complex present in all oxygenic photosynthetic organisms (cyanobacteria, algae, and higher plants). Current high-resolution structures of thermophilic cyanobacterial PSII (3, 4), and lower resolution structures of the red algal (5) and higher plant photosystems (6), have been critically important in furthering our understanding of the molecular organization of PSII. Structurally, the PSII reaction center core is composed of five proteins: D1, D2, the α-and β-subunits of cytochrome b 559 , and PsbI. These components bind all of the redox-active cofactors of PSII.Excitation energy transfer and electron transport within PSII are unavoidably associated with production of reactive oxygen species (ROS) when the absorption of light by the chlorophyll antenna exceeds the capacity for energy utilization. Many mechanisms for ROS production have been proposed (for reviews, see refs. 7 and 8). Briefly, singlet oxygen ( 1 O 2 ) may be formed by excitation energy transfer from triplet chlorophylls (formed either by the change in orientation of the spin of an excited electron in the PSII antenna complex, or via charge recombination of the primary radical pair 3 [P 680 •+ Pheo •− ]) to O 2 (9, 10). ROS production by electron transport involves either the two-electron oxidation of water or the one-electron reduction of O 2 on the PSII electron donor and acceptor sides, respectively. On the PSII electron donor side, a twoelectron oxidation of water leads to the formation of hydrogen peroxide (H 2 O 2 ), which may be oxidized to the superoxide anion radical (O 2•−

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“…Superoxide (O 2 2 ) and nonheme Fe can interact and generate a chain reaction producing hydroxyl radicals ( . OH) through Fenton chemistry (Pospisil et al, 2004).…”

Section: Generation Of Hydroxyl Radicals By the Nonheme Fe Of Psiimentioning

confidence: 99%

Metal Homeostasis in Cyanobacteria and Chloroplasts. Balancing Benefits and Risks to the Photosynthetic Apparatus

2006

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Iron (Fe), manganese (Mn), magnesium (Mg), and copper (Cu) are essential cofactors for the operation of the oxygenic photosynthetic electron transfer apparatus. The overall metal quota required by photosynthetic organisms because of these processes is much larger than the requirement of nonphotosynthetic organisms. To ensure an adequate supply of metals, photosynthetic organisms from cyanobacteria to vascular plants have developed efficient strategies for metal uptake and accumulation. However, the photosynthetic apparatus presents unique challenges to metal homeostasis. Whereas metals play a key role as cofactors in oxygenic photosynthesis, they pose at the same time a major oxidative risk factor due to their deleterious interaction with oxygen. The extreme redox chemistry performed by the two photosystems provides multiple sites at which reactive oxygen species (ROS) can be generated. Therefore, metal transport and storage need to be tightly regulated to ensure adequate supply and to protect against oxidative damage. The proliferation of all photosynthetic organisms depends on this delicate balance between the metal requirements and oxidative damage. This Update focuses on metal biology from a photosynthetic perspective, detailing strategies for metal uptake, accumulation, and cofactor assembly, as well as the inherent risks of metal homeostasis in cyanobacteria and chloroplasts.Oxygenic photosynthesis exerts unique stresses on photosynthetic organisms. The photosynthetic apparatus is composed of a number of membrane-embedded protein supercomplexes that contain many cofactors (Fig.

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Hydroxyl Radical Generation by Photosystem II

Cited by 120 publications

References 73 publications

Photosynthetic water oxidation at elevated dioxygen partial pressure monitored by time-resolved X-ray absorption measurements

Photosynthetic water oxidation at elevated dioxygen partial pressure monitored by time-resolved X-ray absorption measurements

Amino acid oxidation of the D1 and D2 proteins by oxygen radicals during photoinhibition of Photosystem II

Metal Homeostasis in Cyanobacteria and Chloroplasts. Balancing Benefits and Risks to the Photosynthetic Apparatus

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