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Bicarbonate-controlled reduction of oxygen by the Q A semiquinone in Photosystem II in membranes. Proc Natl Acad Sci U S A 2022; 119:2116063119. [PMID: 35115403 PMCID: PMC8833163 DOI: 10.1073/pnas.2116063119] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/23/2021] [Indexed: 12/15/2022] Open
Abstract
In Photosystem II (PSII), O2 reduction by QA•− is often discussed but has not been demonstrated. Here, we show in PSII membranes that QA•− can reduce O2 to superoxide, but only when bicarbonate is absent from its binding site on the nonheme Fe2+. Bicarbonate’s role in PSII was recently shown to involve a regulatory/protective redox-tuning mechanism linking PSII function to CO2 concentration. A key aspect is the presence of stable QA•− causing release of bicarbonate from its site on Fe2+. Here, we show that under these conditions, O2 binds to the empty site on the Fe2+ and is reduced by QA•−. This unexpected reaction may be a further indication of cross-talk between the regulation of PSII and CO2 fixation. Photosystem II (PSII), the water/plastoquinone photo-oxidoreductase, plays a key energy input role in the biosphere. QA•−, the reduced semiquinone form of the nonexchangeable quinone, is often considered capable of a side reaction with O2, forming superoxide, but this reaction has not yet been demonstrated experimentally. Here, using chlorophyll fluorescence in plant PSII membranes, we show that O2 does oxidize QA•− at physiological O2 concentrations with a t1/2 of 10 s. Superoxide is formed stoichiometrically, and the reaction kinetics are controlled by the accessibility of O2 to a binding site near QA•−, with an apparent dissociation constant of 70 ± 20 µM. Unexpectedly, QA•− could only reduce O2 when bicarbonate was absent from its binding site on the nonheme iron (Fe2+) and the addition of bicarbonate or formate blocked the O2-dependant decay of QA•−. These results, together with molecular dynamics simulations and hybrid quantum mechanics/molecular mechanics calculations, indicate that electron transfer from QA•− to O2 occurs when the O2 is bound to the empty bicarbonate site on Fe2+. A protective role for bicarbonate in PSII was recently reported, involving long-lived QA•− triggering bicarbonate dissociation from Fe2+ [Brinkert et al., Proc. Natl. Acad. Sci. U.S.A. 113, 12144–12149 (2016)]. The present findings extend this mechanism by showing that bicarbonate release allows O2 to bind to Fe2+ and to oxidize QA•−. This could be beneficial by oxidizing QA•− and by producing superoxide, a chemical signal for the overreduced state of the electron transfer chain.
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Karacan MS, Rodionova MV, Tunç T, Venedik KB, Mamaş S, Shitov AV, Zharmukhamedov SK, Klimov VV, Karacan N, Allakhverdiev SI. Characterization of nineteen antimony(III) complexes as potent inhibitors of photosystem II, carbonic anhydrase, and glutathione reductase. PHOTOSYNTHESIS RESEARCH 2016; 130:167-182. [PMID: 26932934 DOI: 10.1007/s11120-016-0236-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Accepted: 02/12/2016] [Indexed: 05/16/2023]
Abstract
Nineteen antimony(III) complexes were obtained and examined as possible herbicides. Six of these were synthesized for the first time, and their structures were identified using elemental analyses, 1H-NMR, 13C-NMR, FTIR, LCMS, magnetic susceptibility, and conductivity measurement techniques. For the nineteen examined antimony(III) complexes their most-stable forms were determined by DFT/B3LYP/LanL2DZ calculation method. These compounds were examined for effects on photosynthetic electron transfer and carbonic anhydrase activity of photosystem II, and glutathione reductase from chloroplast as well were investigated. Our results indicated that all antimony(III) complexes inhibited glutathione reductase activity of chloroplast. A number of these also exhibited good inhibitory efficiency of the photosynthetic and carbonic anhydrase activity of Photosystem II.
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Affiliation(s)
- Mehmet Sayım Karacan
- Department of Chemistry, Science Faculty, Gazi University, Teknikokullar, Ankara, Turkey.
| | - Margarita V Rodionova
- Controlled Photobiosynthesis Laboratory, Institute of Plant Physiology, Russian Academy of Sciences, Botanicheskaya Street 35, Moscow, Russia, 127276
| | - Turgay Tunç
- Department of Chemistry and Process Engineering, Engineering and Architecture Faculty, Ahi Evran University, Kırşehir, Turkey
| | - Kübra Begüm Venedik
- Department of Chemistry, Science Faculty, Gazi University, Teknikokullar, Ankara, Turkey
| | - Serhat Mamaş
- Department of Chemistry, Science Faculty, Gazi University, Teknikokullar, Ankara, Turkey
| | - Alexandr V Shitov
- Institute of Basic Biological Problems, Russian Academy of Sciences, Institutskaya Street 2, Pushchino, Moscow Region, Russia, 142290
| | - Sergei K Zharmukhamedov
- Institute of Basic Biological Problems, Russian Academy of Sciences, Institutskaya Street 2, Pushchino, Moscow Region, Russia, 142290
| | - Vyacheslav V Klimov
- Institute of Basic Biological Problems, Russian Academy of Sciences, Institutskaya Street 2, Pushchino, Moscow Region, Russia, 142290
| | - Nurcan Karacan
- Department of Chemistry, Science Faculty, Gazi University, Teknikokullar, Ankara, Turkey.
| | - Suleyman I Allakhverdiev
- Controlled Photobiosynthesis Laboratory, Institute of Plant Physiology, Russian Academy of Sciences, Botanicheskaya Street 35, Moscow, Russia, 127276.
- Institute of Basic Biological Problems, Russian Academy of Sciences, Institutskaya Street 2, Pushchino, Moscow Region, Russia, 142290.
- Department of Plant Physiology, Faculty of Biology, M.V. Lomonosov Moscow State University, Leninskie Gory 1-12, Moscow, Russia, 119991.
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Ananyev G, Gates C, Dismukes GC. The Oxygen quantum yield in diverse algae and cyanobacteria is controlled by partitioning of flux between linear and cyclic electron flow within photosystem II. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2016; 1857:1380-1391. [PMID: 27117512 DOI: 10.1016/j.bbabio.2016.04.056] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2015] [Revised: 04/20/2016] [Accepted: 04/21/2016] [Indexed: 01/07/2023]
Abstract
We have measured flash-induced oxygen quantum yields (O2-QYs) and primary charge separation (Chl variable fluorescence yield, Fv/Fm) in vivo among phylogenetically diverse microalgae and cyanobacteria. Higher O2-QYs can be attained in cells by releasing constraints on charge transfer at the Photosystem II (PSII) acceptor side by adding membrane-permeable benzoquinone (BQ) derivatives that oxidize plastosemiquinone QB(-) and QBH2. This method allows uncoupling PSII turnover from its natural regulation in living cells, without artifacts of isolating PSII complexes. This approach reveals different extents of regulation across species, controlled at the QB(-) acceptor site. Arthrospira maxima is confirmed as the most efficient PSII-WOC (water oxidizing complex) and exhibits the least regulation of flux. Thermosynechococcus elongatus exhibits an O2-QY of 30%, suggesting strong downregulation. WOC cycle simulations with the most accurate model (VZAD) show that a light-driven backward transition (net addition of an electron to the WOC, distinct from recombination) occurs in up to 25% of native PSIIs in the S2 and S3 states, while adding BQ prevents backward transitions and increases the lifetime of S2 and S3 by 10-fold. Backward transitions occur in PSIIs that have plastosemiquinone radicals in the QB site and are postulated to be physiologically regulated pathways for storing light energy as proton gradient through direct PSII-cyclic electron flow (PSII-CEF). PSII-CEF is independent of classical PSI/cyt-b6f-CEF and provides an alternative proton translocation pathway for energy conversion. PSII-CEF enables variable fluxes between linear and cyclic electron pathways, thus accommodating species-dependent needs for redox and ion-gradient energy sources powered by a single photosystem.
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Affiliation(s)
- Gennady Ananyev
- The Waksman Institute of Microbiology and the Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, NJ 08854, United States
| | - Colin Gates
- The Waksman Institute of Microbiology and the Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, NJ 08854, United States
| | - G Charles Dismukes
- The Waksman Institute of Microbiology and the Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, NJ 08854, United States.
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Longatte G, Rappaport F, Wollman FA, Guille-Collignon M, Lemaître F. Mechanism and analyses for extracting photosynthetic electrons using exogenous quinones – what makes a good extraction pathway? Photochem Photobiol Sci 2016; 15:969-79. [DOI: 10.1039/c6pp00076b] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The extraction of photosynthetic electrons by exogenous quinones on unicellular green algae was investigated with fluorescence measurements. Zone diagrams were built for defining the most appropriate harvesting conditions.
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Affiliation(s)
- G. Longatte
- Ecole normale supérieure
- PSL Research University
- UPMC Univ Paris 06
- CNRS
- Département de Chimie
| | - F. Rappaport
- Laboratoire de physiologie membranaire et moléculaire du chloroplaste
- CNRS
- UPMC UMR 7141
- I.B.PC
- 75005 Paris
| | - F.-A. Wollman
- Laboratoire de physiologie membranaire et moléculaire du chloroplaste
- CNRS
- UPMC UMR 7141
- I.B.PC
- 75005 Paris
| | - M. Guille-Collignon
- Ecole normale supérieure
- PSL Research University
- UPMC Univ Paris 06
- CNRS
- Département de Chimie
| | - F. Lemaître
- Ecole normale supérieure
- PSL Research University
- UPMC Univ Paris 06
- CNRS
- Département de Chimie
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Torre P, Sassano CE, Sato S, Converti A, Gioielli LA, Carvalho JC. Fed-batch addition of urea for Spirulina platensis cultivation. Enzyme Microb Technol 2003. [DOI: 10.1016/s0141-0229(03)00217-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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7
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van Rensen JJ, Tonk WJ, de Bruijn SM. Involvement of bicarbonate in the protonation of the secondary quinone electron acceptor of photosystem II via the non-haem iron of the quinone-iron acceptor complex. FEBS Lett 2001. [DOI: 10.1016/0014-5793(88)81452-2] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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8
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Volkov AG, Gugeshashvili MI, Deamer DW. Energy conversion at liquid/liquid interfaces: artificial photosynthetic systems. Electrochim Acta 2001; 40:2849-68. [PMID: 11540307 DOI: 10.1016/0013-4686(95)00214-y] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
This chapter focuses on multielectron reactions in organized assemblies of molecules at the liquid/liquid interface. We describe the thermodynamic and kinetic parameters of such reactions, including the structure of the reaction centers, charge movement along the electron transfer pathways, and the role of electric double layers in artificial photosynthesis. Some examples of artificial photosynthesis at the oil/water interface are considered, including water photooxidation to the molecular oxygen, oxygen photoreduction, photosynthesis of amphiphilic compounds and proton evolution by photochemical processes.
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Affiliation(s)
- A G Volkov
- Department of Chemistry, University of California, Santa Cruz 95064, USA
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Wiessner W, Mende D, Demeter S. Thermoluminescence study of the in vivo effects of bicarbonate depletion and acetate/formate presence in the two algae Chlamydobotrys stellata and Chlamydomonas reinhardtii. PHOTOSYNTHESIS RESEARCH 1992; 34:279-285. [PMID: 24408779 DOI: 10.1007/bf00033445] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/1992] [Accepted: 07/01/1992] [Indexed: 06/03/2023]
Abstract
We investigated the influence of CO2/HCO3 (-)-depletion and of the presence of acetate and formate on the in vivo photosynthetic electron transport in the two green algae Chlamydobotrys stellata and Chlamydomonas reinhardtii by means of thermoluminescence technique and mathematical glow curve analysis. The main effects of the removal of CO2 from the algal cultures was: (1) A shift of the glow curve peak position to lower temperatures resulting from a decrease of the B band and an increase of the Q band. (2) Treatment of CO2-deficient Chl. stellata with DCMU yielded two thermoluminescence bands in the Q band region peaking at around +12°C and +5°C; in case of Chl. reinhardtii DCMU treatment induced only one band with an emission maximum at +5°C. The presence of acetate or formate in CO2-depleted algal cultures lowered the intensities of all of the individual TL bands but that of a HT band (TL+37). The effects of CO2-depletion and of the presence of anions were fully reversible.
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Affiliation(s)
- W Wiessner
- Pflanzenphysiologisches Institut der Universität Göttingen, Untere Karspüle 2, D-3400, Göttingen, Germany
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11
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Drechsler Z, Neumann J. A differential effect of 3-(3'4' dichlorophenyl)-1,1 dimethyl urea and atrazine on fluorescence kinetics in chloroplasts. PHOTOSYNTHESIS RESEARCH 1992; 31:139-148. [PMID: 24407985 DOI: 10.1007/bf00028790] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/1991] [Accepted: 11/07/1991] [Indexed: 06/03/2023]
Abstract
It was found that DCMU had a differential effect at two concentration ranges on variable fluorescence kinetics in isolated chloroplasts. The increase in fluorescence rate at low concentrations of DCMU was abolished by preincubation of chloroplasts with ferricyanide or formate, treatments which were shown to convert Fe in the PS II reaction center (i.e., the FeQA complex) into a non-oxidizable form, but it was not affected by Tris treatment. Increase in fluorescence kinetics (at the initial linear rate) at high concentrations of DCMU was found to be abolished by Tris treatment but it was only marginally affected by ferricyanide or formate treatments. The effect of Tris could be abolished by addition of hydroquinone-ascorbate, which restored electron flow to the pool of secondary acceptors.Contrary to the effect of DCMU, no such differential concentration dependence of the variable fluorescence kinetics was found for atrazine.The increase in fluorescence kinetics (at the initial linear rate) at a low concentration rate of DCMU is presumably restricted to units which contain an oxidizable Fe in the FeQA complex. Increase in fluorescence kinetics (at the initial linear rate) at high DCMU concentration is probably related to the effect of DCMU at the QB site.
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Affiliation(s)
- Z Drechsler
- Department of Botany, The George S. Wise Faculty of Life Sciences, Tel Aviv University, 69978, Tel Aviv, Israel
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12
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Xu C, Taoka S, Crofts AR, Govindjee. Kinetic characteristics of formate/formic acid binding at the plastoquinone reductase site in spinach thylakoids. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1991. [DOI: 10.1016/0005-2728(91)90006-a] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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13
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El-Shintinawy F. Bicarbonate effects in leaf discs from spinach. PHOTOSYNTHESIS RESEARCH 1990; 24:189-200. [PMID: 24420071 DOI: 10.1007/bf00032306] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/1989] [Accepted: 12/12/1989] [Indexed: 05/08/2023]
Abstract
In this paper, we show the unique role of bicarbonate ion in stimulating the electron transfer of photosystem II (PS II) in formate-treated leaf discs from spinach. This is referred to as the "bicarbonate effect" and is independent of the role of CO2 in CO2 fixation. It is shown to have two sites of action: (1) the first, described here for the first time, stimulates the electron flow between the hydroxylamine donation site ("Z" or "D") and QA, the first plastoquinone electron acceptor and (2) the other accelerates the electron flow beyond QA, perhaps at the QA QB complex, where QB is the second plastoquinone electron acceptor. The first site of inhibition by formate-treatment is detected by the decrease of the rate of oxygen evolution and the simultaneous quenching of the variable chlorophyll a (Chl a) fluorescence of leaf discs infiltrated with 100 mM formate for about 10 s followed by storage for 10 min in dark. This is referred to as short-term formate treatment. Addition of bicarbonate reverses this short-term formate effect and restores fully both Chl a fluorescence and oxygen evolution rate. Reversible quenching of variable Chl a fluorescence of heated and short-term formate treated leaf discs, in the presence of hydroxylamine as an artificial electron donor to PS II, is also observed. This suggests that the first site of action of the anion effect is indeed between the site of donation of hydroxylamine to PS II (i.e. "Z" or "D") and QA. The second site of the effect, where bicarbonate depletion has its most dramatic effect, as well known in thylakoids, is shown by an increase of Chl a fluorescence of leaf discs infiltrated with 100 mM formate for about 10 min followed by storage for 10 min in dark. This is referred to as the long-term formate treatment. Addition of bicarbonate fully restores the variable Chl a fluorescence of these leaf discs. Chl a fluorescence transient of DCMU-infiltrated (10 min) leaf discs is similar to that of long-term formate-treated one suggesting that the absence of bicarbonate, like the presence of DCMU, inhibits the electron flow beyond QA.
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Affiliation(s)
- F El-Shintinawy
- Department of Physiology & Biophysics and Plant Biology, University of Illinois, 289 Morrill Hall, 505 South Goodwin Avenue, 61801-3793, Urbana, Illinois, USA
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14
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Hansson O, Wydrzynski T. Current perceptions of Photosystem II. PHOTOSYNTHESIS RESEARCH 1990; 23:131-162. [PMID: 24421057 DOI: 10.1007/bf00035006] [Citation(s) in RCA: 134] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/02/1989] [Accepted: 06/05/1989] [Indexed: 06/03/2023]
Abstract
In the last few years our knowledge of the structure and function of Photosystem II in oxygen-evolving organisms has increased significantly. The biochemical isolation and characterization of essential protein components and the comparative analysis from purple photosynthetic bacteria (Deisenhofer, Epp, Miki, Huber and Michel (1984) J Mol Biol 180: 385-398) have led to a more concise picture of Photosystem II organization. Thus, it is now generally accepted that the so-called D1 and D2 intrinsic proteins bind the primary reactants and the reducing-side components. Simultaneously, the nature and reaction kinetics of the major electron transfer components have been further clarified. For example, the radicals giving rise to the different forms of EPR Signal II have recently been assigned to oxidized tyrosine residues on the D1 and D2 proteins, while the so-called Q400 component has been assigned to the ferric form of the acceptor-side iron. The primary charge-separation has been meaured to take place in about 3 ps. However, despite all recent major efforts, the location of the manganese ions and the water-oxidation mechanism still remain largely unknown. Other topics which lately have received much attention include the organization of Photosystem II in the thylakoid membrane and the role of lipids and ionic cofactors like bicarbonate, calcium and chloride. This article attempts to give an overall update in this rapidly expanding field.
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Affiliation(s)
- O Hansson
- Department of Biochemistry and Biophysics, Chalmers University of Technology, S-412 96, Göteborg, Sweden
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15
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Havaux M. Photoacoustic characteristics of leaves of atrazine-resistant weed mutants. PHOTOSYNTHESIS RESEARCH 1989; 21:51-59. [PMID: 24424493 DOI: 10.1007/bf00047175] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/1988] [Accepted: 09/26/1988] [Indexed: 06/03/2023]
Abstract
The photosynthetic characteristics of leaves of atrazine-resistant and-susceptible biotypes of several weed species (Solanum nigrum, Senecio vulgaris, Epilobium ciliatum and Chenopodium album) were compared using the photoacoustic method. Analysis of the dependence of the photoacoustic signal of the modulation frequency indicated that, in Solanum, Epilobium and Senecio, the relative quantum yield of O2 evolution ϕ (estimated by the ratio of the amplitude of the O2 signal, AOX, to that of the photothermal signal, APT) was substantially reduced in the atrazine-resistant mutant, without any changes in the O2 diffusion characteristics of the leaves. In contrast, in Chenopodium, atrazine-resistance was associated with a concomitant change in ϕ and in the leaf diffusion parameters. This latter change suggests that the leaf internal anatomy was modified in the resistant Chenopodium. Measurements of the Emerson enhancement indicated that the reduction of ϕ observed in the atrazine-resistant mutants was caused by a marked decrease in the photochemical potential of PS II (β). The study of the light intensity dependence of the AOX/APT ratio showed that saturation of O2 evolution occurred at the same light level (around 2000 μmol m(-2) s(-1)) in both types of plants. However, the relative maximal rate of O2 evolution was slightly lower (-10%) in the atrazine-resistant biotype as compared to the wild type. Reduced ϕ and light-saturated rate of O2 evolution were also measured in atrazine-resistant weed biotypes using a conventional Clark-type O2 electrode.
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Affiliation(s)
- M Havaux
- Laboratoire de Physiologie végétale (CP 169), Université Libre de Bruxelles, 28 Avenue P. Heger, B-1050, Brussels, Belgium
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Shopes RJ, Blubaugh DJ, Wraight CA, Govindjee. Absence of a bicarbonate-depletion effect in electron transfer between quinones in chromatophores and reaction centers of Rhodobacter sphaeroides. BIOCHIMICA ET BIOPHYSICA ACTA 1989; 974:114-8. [PMID: 2647143 DOI: 10.1016/s0005-2728(89)80171-9] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Higher plants, algae, and cyanobacteria are known to require bicarbonate ions for electron flow from the first stable electron acceptor quinone QA to the second electron acceptor quinone QB, and to the intersystem quinone pool. It has been suggested that in Photosystem II of oxygenic photosynthesis, bicarbonate ion functions to maintain the reaction center in a proper conformation and, perhaps, to provide the protons needed to stabilize the semiquinone (QB-). In this paper, we show that bicarbonate ions do not influence the electron flow, from the quinone QA to QB and beyond, in the photosynthetic bacterium Rhodobacter sphaeroides. No measurable effect of bicarbonate depletion, obtained by competition with formate, was observed on cytochrome b-561 reduction in chromatophores; on the flash-dependent oscillation of semiquinone formation in reaction centers; on electron transfer from QA- to QB; or on either the fast or slow recovery of the oxidized primary donor (P+) which reflects the P+QA- ----PQA or the P+QB- ----PQB reaction. The lack of an observed effect in Rhodobacter sphaeroides in contrast to the effect seen in Photosystem II is suggested to be due to the amino-acid sequence differences between the reaction centers of the two systems.
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Affiliation(s)
- R J Shopes
- Department of Physiology and Biophysics, University of Illinois, Urbana
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17
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Bicarbonate does not influence electron transfer to the reaction center chlorophyll a of photosystem II. Naturwissenschaften 1989. [DOI: 10.1007/bf00366603] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Volkov AG. Oxygen evolution in the course of photosynthesis: molecular mechanisms. J Electroanal Chem (Lausanne) 1989. [DOI: 10.1016/0022-0728(89)87188-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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20
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Blubaugh DJ, Govindjee. Kinetics of the bicarbonate effect and the number of bicarbonate-binding sites in thylakoid membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1988. [DOI: 10.1016/0005-2728(88)90237-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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21
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Eaton-Rye JJ, Govindjee. Electron transfer through the quinone acceptor complex of Photosystem II after one or two actinic flashes in bicarbonate-depleted spinach thylakoid membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1988. [DOI: 10.1016/0005-2728(88)90221-6] [Citation(s) in RCA: 62] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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22
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Garab G, Rozsa Z, Govindjee. Carbon dioxide affects charge accumulation in leaves. Naturwissenschaften 1988. [DOI: 10.1007/bf00361289] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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23
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Electron transfer through the quinone acceptor complex of Photosystem II in bicarbonate-depleted spinach thylakoid membranes as a function of actinic flash number and frequency. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1988. [DOI: 10.1016/0005-2728(88)90220-4] [Citation(s) in RCA: 66] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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24
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Blubaugh DJ. The molecular mechanism of the bicarbonate effect at the plastoquinone reductase site of photosynthesis. PHOTOSYNTHESIS RESEARCH 1988; 19:85-128. [PMID: 24425370 DOI: 10.1007/bf00114571] [Citation(s) in RCA: 62] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/1987] [Accepted: 03/30/1988] [Indexed: 05/12/2023]
Abstract
It has been known for some time that bicarbonate reverses the inhibition, by formate under HCO3 (-)-depletion conditions, of electron transport in thylakoid membranes. It has been shown that the major effect is on the electron acceptor side of photosystem II, at the site of plastoquinone reduction. After presenting a historical introduction, and a minireview of the bicarbonate effect, we present a hypothesis on how HCO3 (-) functions in vivo as (a) a proton donor to the plastoquinone reductase site in the D1-D2 protein; and (b) a ligand to Fe(2+) in the QA-Fe-QB complex that keeps the D1-D2 proteins in their proper functional conformation. They key points of the hypothesis are: (1) HCO3 (-) forms a salt bridge between Fe(2+) and the D2 protein. The carboxyl group of HCO3 (-) is a bidentate ligand to Fe(2+), while the hydroxyl group H-bonds to a protein residue. (2) A second HCO3 (-) is involved in protonating a histidine near the QB site to stabilize the negative charge on QB. HCO3 (-) provides a rapidly available source of H(+) for this purpose. (3) After donation of a H(+), CO3 (2-) is replaced by another HCO3 (-). The high pKa of CO3 (2-) ensures rapid reprotonation from the bulk phase. (4) An intramembrane pool of HCO3 (-) is in equilibrium with a large number of low affinity sites. This pool is a H(+) buffering domain functionally connecting the external bulk phase with the quinones. The low affinity sites buffer the intrathylakoid [HCO3 (-)] against fluctuations in the intracellular CO2. (5) Low pH and high ionic strength are suggested to disrupt the HCO3 (-) salt bridge between Fe(2+) and D2. The resulting conformational change exposes the intramembrane HCO3 (-) pool and low affinity sites to the bulk phase.Two contrasting hypotheses for the action of formate are: (a) it functions to remove bicarbonate, and the low electron transport left in such samples is due to the left-over (or endogenous) bicarbonate in the system; or (b) bicarbonate is less of an inhibitor and so appears to relieve the inhibition by formate. Hypothesis (a) implies that HCO3 (-) is an essential requirement for electron transport through the plastoquinones (bound plastoquinones QA and QB and the plastoquinone pool) of photosystem II. Hypothesis (b) implies that HCO3 (-) does not play any significant role in vivo. Our conclusion is that hypothesis (a) is correct and HCO3 (-) is an essential requirement for electron transport on the electron acceptor side of PS II. This is based on several observations: (i) since HCO3 (-), not CO2, is the active species involved (Blubaugh and Govindjee 1986), the calculated concentration of this species (220 μM at pH 8, pH of the stroma) is much higher than the calculated dissociation constant (Kd) of 35-60 μM; thus, the likelihood of bound HCO3 (-) in ambient air is high; (ii) studies on HCO3 (-) effect in thylakoid samples with different chlorophyll concentrations suggest that the "left-over" (or "endogenous") electron flow in bicarbonate-depleted chloroplasts is due to "left-over" (or endogenous) HCO3 (-) remaining bound to the system (Blubaugh 1987).
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Affiliation(s)
- D J Blubaugh
- Department of Physiology & Biophysics, University of Illinois, 289 Morrill Hall, 505, South Goodwin Avenue, 61801, Urbana, IL, USA
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Jursinic P, Stemler A. Multiple anion effects on photosystem II in chloroplast membranes. PHOTOSYNTHESIS RESEARCH 1988; 15:41-56. [PMID: 24430791 DOI: 10.1007/bf00054987] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/1987] [Accepted: 08/07/1987] [Indexed: 06/03/2023]
Abstract
We investigated the activity of several anions at various sites on photosystem II, in particular those associated with the Cl(-) effect (anion binding-site I) and the HCO3 (-) effect (anion binding-site II). Chlorophyll a fluorescence changes were used to monitor partial photosystem II reactions either in the oxygen-evolving mechanism or involving endogenous quinone electron acceptors. We find that anions such as NO3 (-), HCO3 (-), HCO2 (-), F(-), NO2 (-), and acetate can, depending on conditions, bind to either anion binding-site I, anion binding-site II, or both sites simultaneously. The anions N3 (-) and Au(CN)2 (-) are exceptions. In their presence, oxygen-consumption reactions are enhanced. The results demonstrate that an exclusive site or mode of action of an anion on photosystem II cannot be determined by measuring the Hill reaction alone. Anion interactions with photosystem II are shown to be very complex and, therefore, caution is advisable in interpreting related experiments. Carbonic anhydrase associated with photosystem II was also investigated as a possible target for some anion effects. In Cl(-)-depleted thylakoids, NO3 (-), stimulated both electron transport and carbonic anhydrase activity at low concentrations, while higher concentrations inhibited both. However, carbonic anhydrase was more sensitive to inhibition by NO3 (-) than was electron flow. Possible interpretations are discussed; the electron transport and carbonic anhydrase activity appear not to be functionally linked.
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Affiliation(s)
- P Jursinic
- Department de Biologie, Service de Radioagronomie, Centre d'Etudes Nucléaires de Cadarache, F-13108, Saint-Paul-Lez-Durance, France
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Ireland CR, Baker NR, Long SP. Evidence for a physiological role of CO2 in the regulation of photosynthetic electron transport in intact leaves. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1987. [DOI: 10.1016/0005-2728(87)90095-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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