Oxygen release time in leaf discs and thylakoids of peas and Photosystem II membrane fragments of spinach

Jursinic, Paul A.; Dennenberg, Ronald J.

doi:10.1016/0005-2728(90)90051-5

Cited by 37 publications

(27 citation statements)

References 30 publications

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“…The first is the normal process of photosynthetic 02 evolution from water that can be seen in control PS II membrane fragments and in treated membranes on the third and subsequent flashes. This type of 02 production is associated with 02 release times on the order of 3-6 ms as has been reported by other groups (see Jursinic andDennenberg 1990, Lavorel 1992, and references therein). Two mechanisms of anomalous 02 release are seen in NH2OH-and HzO2-treated PS II membranes and are characterized by O2-release times of around 20 ms and 120 ms, respectively.…”

Section: Discussionsupporting

confidence: 49%

“…2 and 3; Table 1) were obtained with a modified bare platinum electrode as described previously (Jursinic and Dennenberg 1990) except that the above mentioned flow buffer was used, the flashes were spaced 1 s apart, and the bias voltage applied to the Pt was -0.6 V versus the Ag/AgC1 electrode. The apparatus had an electronic response time of 0.5 ms. PS II membranes were incubated in buffer A containing either NH2OH or no addition for 5 min in the dark and then transferred to a syringe.…”

Section: Methodsmentioning

confidence: 99%

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Slow oxygen release on the first two flashes in chemically stressed Photosystem II membrane fragments results from hydrogen peroxide oxidation

1993

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Flash-induced amperometric signals were measured with a Joliot-type O2 rate electrode in spinach Photosystem II (PS II) membrane fragments exposed to very low concentrations of added hydroxylamine or hydrogen peroxide. In both cases 'anomalous O2 signals' were observed on the first two flashes, and oscillating four-flash patterns were observed on subsequent flashes. The anomalous signals were eliminated in the presence of catalase but not EDTA. The rise times of the O2-release kinetics associated with the anomalous signals were slow (ca. 20 ms with NH2OH and ca. 120 ms with H2O2) compared to the kinetics of O2 release on subsequent flashes and in control membranes (3-6 ms). It is proposed that when the intact PS II O2-evolving complex is perturbed with small concentrations of added reductant, H2O2 can gain access and bind to the complex. Bound H2O2 can then reduce lower S states in some centers leading to anomalous O2 signals on the first two flashes. A model is presented to explain both types of anomalous O2 production. Oxygen observed on the third and subsequent flashes is due to the normal photosynthetic O2-evolution process arising from the S3-state. Anomalous O2 production could be a protective mechanism in PS II centers subjected to stress conditions.

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Section: Discussionsupporting

confidence: 49%

Section: Methodsmentioning

confidence: 99%

Slow oxygen release on the first two flashes in chemically stressed Photosystem II membrane fragments results from hydrogen peroxide oxidation

1993

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“…This coincidence has been well documented by a wealth of independent techniques. (i) The appearance of O 2 in solution was time resolved by four different techniques, namely continuous flow (9), EPR (10,11), polarography with a bare Pt electrode (2,(12)(13)(14) and via absorption changes of intracellular cytochrome c oxidase (15). (ii) The reduction of Y Z ox was detected by timeresolved EPR (10,16,17), and (iii) the reduction of the Mn 4 O x Ca cluster by UV absorption (7,12,(18)(19)(20), delayed chlorophyll fluorescence (DF) (21), and time-resolved Mn-K-edge spectroscopy (8,22).…”

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confidence: 99%

Membrane-inlet mass spectrometry reveals a high driving force for oxygen production by photosystem II

Shevela

Beckmann

Clausen

et al. 2011

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

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Oxygenic photosynthesis is the basis for aerobic life on earth. The catalytic Mn 4 O x CaY Z center of photosystem II (PSII), after fourfold oxidation, extracts four electrons from two water molecules to yield dioxygen. This reaction cascade has appeared as a single four-electron transfer that occurs in typically 1 ms. Inevitable redox intermediates have so far escaped detection, probably because of very short lifetime. Previous attempts to stabilize intermediates by high O 2 -back pressure have revealed controversial results. Here we monitored by membrane-inlet mass spectrometry (MIMS) the production of 18 O 2 from 18 O-labeled water against a high background of 16 O 2 in a suspension of PSII-core complexes. We found neither an inhibition nor an altered pattern of O 2 production by up to 50-fold increased concentration of dissolved O 2 . Lack of inhibition is in line with results from previous X-ray absorption and visible-fluorescence experiments, but contradictory to the interpretation of previous UV-absorption data. Because we used essentially identical experimental conditions in MIMS as had been used in the UV work, the contradiction was serious, and we found it was not to be resolved by assuming a significant slowdown of the O 2 release kinetics or a subsequent slow conformational relaxation. This calls for reevaluation of the less direct UV experiments. The direct detection of O 2 release by MIMS shows unequivocally that O 2 release in PSII is highly exothermic. Under the likely assumption that one H þ is released in the S 4 → S 0 transition, the driving force at pH 6.5 and atmospheric O 2 pressure is at least 220 meV, otherwise 160 meV.water oxidation | oxygen evolution | isotope-ratio mass spectrometry | bioenergetics O xygenic photosynthesis is the metabolic basis for the most successful forms of life on earth. In cyanobacteria, algae and plants photosystem II (PSII) uses sunlight to split water into dioxygen and reducing equivalents, and it generates proton motive force. The catalytic centre of O 2 production in PSII, coined the OEC (oxygen evolving complex), comprises the manganese-oxygen-calcium (Mn 4 O x Ca) complex and its ligands, which include two substrate "water" molecules of undefined protonation state. It also includes a redox-active tyrosine residue, coined tyrosine ZðY Z Þ, which is the essential electron transfer link to the photoactive reaction center of PSII. Over 40 years ago Kok et al. (1) proposed-on the basis of flash-induced O 2 -evolution patterns (2)-that PSII, clocked and driven by four quanta of light, cycles through five different redox states, named S i (i ¼ 0;…;4), where i is the number of stored oxidizing equivalents. Once four oxidizing equivalents are accumulated O 2 is produced in the spontaneous reaction from S 4 to yield S 0 .In this S i state transition four electrons are transferred from two bound substrate water molecules that were partially or fully deprotonated (m ¼ 0-2) during the S i state cycle. In addition, one or two new substrate water molecules (n ¼ 1;2) bin...

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“…The depletion of bicarbonate by its analogue formate results in a significant inhibition of the electron transfer on the acceptor side, i.e., from QA to the plastoquinone pool (see references in Blubaugh & Govindjee, 1988a;Govindjee & van Rensen, 1993). Studies have also suggested that bicarbonate may affect the donor side function of PSII (El-Shintinawy & Govindjee, 1990;Jursinic & Dennenberg, 1990;Stemler & Jursinic, 1993;Klimov et al, 1995;Wincencjusz et al, 1996).…”

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confidence: 99%

Modeling of the D1/D2 proteins and cofactors of the photosystem II reaction center: Implications for herbicide and bicarbonate binding

1996

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A three-dimensional model of the photosystem I1 (PSII) reaction center from the cyanobacterium Synechocystis sp. PCC 6803 was generated based on homology with the anoxygenic purple bacterial photosynthetic reaction centers of Rhodobacter sphaeroides and Rhodopseudomonas viridis, for which the X-ray crystallographic structures are available. The model was constructed with an alignment of Dl and D2 sequences with the L and M subunits of the bacterial reaction center, respectively, and by using as a scaffold the structurally conserved regions (SCRs) from bacterial templates. The structurally variant regions were built using a novel sequence-specific approach of searching for the best-matched protein segments in the Protein Data Bank with the "basic local alignment search tool" (Altschul SF, Gish W, Miller W, Myers EW, Lipman DJ, 1990, J Mol Biol 215:403-410). and imposing the matching conformational preference on the corresponding D l and D2 regions. The structure thus obtained was refined by energy minimization. The modeled D l and D2 proteins contain five transmembrane a-helices each, with cofactors (4 chlorophylls, 2 pheophytins, 2 plastoquinones, and a non-heme iron) essential for PSII primary photochemistry embedded in them. A p-carotene, considered important for PSII photoprotection, was also included in the model. Four different possible conformations of the primary electron donor P680 chlorophylls were proposed, one based on the homology with the bacterial template and the other three on existing experimental suggestions in literature. The P680 conformation based on homology was preferred because it has the lowest energy.Redox active tyrosine residues important for P680' reduction as well as residues important for PSI1 cofactor binding were analyzed. Residues involved in interprotein interactions in the model were also identified. Herbicide 3-(3,4-dichlorophenyI)-I , 1 -dimethylurea (DCMU) was also modeled in the plastoquinone QB binding niche using the structural information available from a DCMU-binding bacterial reaction center.A bicarbonate anion, known to play a role in PSII, but not in anoxygenic photosynthetic bacteria, was modeled in the non-heme iron site, providing a bidentate ligand to the iron. By modifying the previous hypothesis of Blubaugh and Govindjee (1988, Photosyn Res 1 9 3 -1 2 8 ) , we modeled a second bicarbonate and a water molecule in the Qe site and we proposed a hypothesis to explain the mechanism of QB protonation mediated by bicarbonate and water. The bicarbonate, stabilized by DLR257, donates a proton to Qi-through the intermediate of DLH252; and a water molecule donates another proton to Qi-. Based on the discovery of a "water transport channel" in the bacterial reaction center, an analogous channel for transporting water and bicarbonate is proposed in our PSII model. The putative channel appears to be primarily positively charged near QB and the non-heme iron, in contrast to the polarity distribution in the bacterial water transport channel. The constructed model has ...

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Oxygen release time in leaf discs and thylakoids of peas and Photosystem II membrane fragments of spinach

Cited by 37 publications

References 30 publications

Slow oxygen release on the first two flashes in chemically stressed Photosystem II membrane fragments results from hydrogen peroxide oxidation

Slow oxygen release on the first two flashes in chemically stressed Photosystem II membrane fragments results from hydrogen peroxide oxidation

Membrane-inlet mass spectrometry reveals a high driving force for oxygen production by photosystem II

Modeling of the D1/D2 proteins and cofactors of the photosystem II reaction center: Implications for herbicide and bicarbonate binding

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