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Canaani O. The effect of chloroplast pH on the distribution of excitation energy between photosystems I and II suggests the involvement of two kinases in state 1-state 2 transitions. FEBS Lett 2002. [DOI: 10.1016/0014-5793(85)80387-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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2
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Forti G, Vianelli A. Influence of thylakoid protein phosphorylation on photosystem I photochemistry. FEBS Lett 2001. [DOI: 10.1016/0014-5793(88)80709-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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3
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O'Connor HE, Ruffle SV, Cain AJ, Deak Z, Vass I, Nugent JH, Purton S. The 9-kDa phosphoprotein of photosystem II. Generation and characterisation of Chlamydomonas mutants lacking PSII-H and a site-directed mutant lacking the phosphorylation site. BIOCHIMICA ET BIOPHYSICA ACTA 1998; 1364:63-72. [PMID: 9554956 DOI: 10.1016/s0005-2728(98)00013-9] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The chloroplast gene psbH encodes a 9-10 kDa thylakoid membrane protein (PSII-H) that is associated with photosystem II and is subject to light-dependent phosphorylation at a threonine residue located on the stromal side of the membrane. The function of PSII-H is not known, neither is it clear what regulatory role phosphorylation may play in the control of PSII activity. Using particle gun-mediated transformation, we have created chloroplast transformants of Chlamydomonas reinhardtii in which the synthesis of PSII-H is prevented by the disruption of psbH, or in which the phosphorylatable threonine is replaced by alanine through site-directed mutagenesis of the gene. The mutants lacking PSII-H have a photosystem II-deficient phenotype, with no detectable functioning PSII complex present in whole cells or isolated thylakoid membranes. In contrast, the alanine mutant (T3A) grows photoautotrophically, and PSII activity is comparable to wild-type cells as determined by various biochemical and biophysical assays.
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Affiliation(s)
- H E O'Connor
- UCL Photosynthesis Group, Department of Biology, University College London, Gower Street, London WC1E 6BT, UK
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4
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Giardi MT, Cona A, Geiken B. Photosystem II core phosphorylation heterogeneity and the regulation of electron transfer in higher plants: a review. ACTA ACUST UNITED AC 1995. [DOI: 10.1016/0302-4598(95)01819-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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5
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Samson G, Fork DC. Simultaneous photoreduction and photooxidation of cytochrome b-559 in Photosystem II treated with carbonylcyanide-m-chlorophenylhydrazone. PHOTOSYNTHESIS RESEARCH 1992; 33:203-212. [PMID: 24408664 DOI: 10.1007/bf00030031] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/1991] [Accepted: 04/14/1992] [Indexed: 06/03/2023]
Abstract
The possibility of a Photosystem II (PS II) cyclic electron flow via Cyt b-559 catalyzed by carbonylcyanide m-chlorophenylhydrazone (CCCP) was further examined by studying the effects of the PS II electron acceptor 2,6-dichloro-p-benzoquinone (DCBQ) on the light-induced changes of the redox states of Cyt b-559. Addition to barley thylakoids of micromolar concentrations of DCBQ completely inhibited the changes of the absorbance difference corresponding to the photoreduction of Cyt b-559 observed either in the presence of 10 μM ferricyanide or after Cyt b-559 photooxidation in the presence of 2 μM CCCP. In CCCP-treated thylakoids, the concentration of photooxidized Cyt b-559 decreased as the irradiance of actinic light increased from 2 to 80 W m(-2) but remained close to the maximal concentration (0.53 photooxidized Cyt b-559 per photoactive Photosystem II) in the presence of 50 μM DCBQ. The stimulation of Cyt b-559 photooxidation in parallel with the inhibition of its photoreduction caused by DCBQ demonstrate that the extent of the light-induced changes of the redox state of Cyt b-559 in the presence of CCCP is determined by the difference between the rates of photooxidation and photoreduction of Cyt b-559 occuring simultaneously in a cyclic electron flow around PS II.We also observed that the Photosystem I electron acceptor methyl viologen (MV) at a concentration of 1 mM barely affected the rate and extent of the light-induced redox changes of Cyt b-559 in the presence of either FeCN or CCCP. Under similar experimental conditions, MV strongly quenched Chl-a fluorescence, suggesting that Cyt b-559 is reduced directly on the reducing side of Photosystem II.
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Affiliation(s)
- G Samson
- Department of Plant Biology, Carnegie Institution of Washington, 290 Panama Street, 49305-1297, Stanford, CA, USA
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6
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Harrison MA, Allen JF. Protein phosphorylation and Mg2+ influence light harvesting and electron transport in chloroplast thylakoid membrane material containing only the chlorophyll-a/b-binding light-harvesting complex of photosystem II and photosystem I. EUROPEAN JOURNAL OF BIOCHEMISTRY 1992; 204:1107-14. [PMID: 1551390 DOI: 10.1111/j.1432-1033.1992.tb16735.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
A material containing only photosystem I (PSI) and the chlorophyll-a/b-binding light-harvesting complex of PSII (LHC-II) has been isolated from the chloroplast thylakoid membrane by solubilization with Triton X-100. Fluorescence spectroscopy shows that, within the material, LHC-II is coupled to PSI for excitation-energy transfer and that this coupling is decreased by the presence of Mg2+, which also decreased PSI electron transport specifically at limiting light intensity. Inclusion of phosphorylated LHC-II within the material did not alter its structure, but gave decreased energy transfer to PSI and inhibition of electron transport which was independent of light intensity, implying effects of phosphorylation on both light harvesting and directly on electron transport. Inclusion of Mg2+ within the phosphorylated material gave decreased energy transfer, but slightly increased PSI electron transport. A cation-induced direct promotion of PSI electron transport was also observed in isolated PSI particles. The PSI/LHC-II material represents a model system for examining protein interactions during light-state adaptations and the possibility that LHC-II can contribute to the antenna of PSI in light state 2 in vivo is discussed.
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Affiliation(s)
- M A Harrison
- Department of Pure and Applied Biology, University of Leeds, England
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7
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Identification, characterization, and resolution of the in vivo phosphorylated form of the D1 photosystem II reaction center protein. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(19)50761-x] [Citation(s) in RCA: 83] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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8
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Allen JF. Protein phosphorylation in regulation of photosynthesis. BIOCHIMICA ET BIOPHYSICA ACTA 1992; 1098:275-335. [PMID: 1310622 DOI: 10.1016/s0005-2728(09)91014-3] [Citation(s) in RCA: 499] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- J F Allen
- Department of Biology, University of Oslo, Blindern, Norway
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9
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Braun G, Malkin S. Quantitative study of state 1-state 2 transitions in broken chloroplasts-comparison to in-vivo properties. PHOTOSYNTHESIS RESEARCH 1992; 31:49-56. [PMID: 24407929 DOI: 10.1007/bf00049536] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/1991] [Accepted: 10/25/1991] [Indexed: 06/03/2023]
Abstract
A detailed quantitative study was conducted on state 1-state 2 transition and its reversal in broken chloroplasts by modulated fluorimetry. The characteristics of the transition obtained supported other previous in-vitro findings. More importantly, a very close quantitative similarity was obtained under suitable conditions to previous in-vivo studies, particularly in approaching a constancy of Fm/F0 during the transition and the equality of the fractional change of these fluorescence parameters with the calculated light distribution fraction to PS II. This confirms that in broken chloroplasts too, the state transitions involve reciprocal changes in the absorption cross-sections of PS II and PS I.
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Affiliation(s)
- G Braun
- Biochemistry Department, The Weizmann Institute of Science, 76100, Rehovot, Israel
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10
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Harrison MA, Allen JF. Light-dependent phosphorylation of Photosystem II polypeptides maintains electron transport at high light intensity: separation from effects of phosphorylation of LHC-II. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1991. [DOI: 10.1016/s0005-2728(05)80249-x] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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11
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Sundby C. Bicarbonate effects on photo-inhibition. Including an explanation for the sensitivity to photo-inhibition under anaerobic conditions. FEBS Lett 1990; 274:77-81. [PMID: 2174804 DOI: 10.1016/0014-5793(90)81333-j] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Isolated thylakoid membranes were found to be efficiently protected against photo-inhibition by sodium bicarbonate (20 mM NaHCO3) under both anaerobic and aerobic conditions. Furthermore, data are presented which indicate that the pronounced sensitivity to photo-inhibition under anaerobic compared to aerobic conditions is due to the removal of protecting bicarbonate, rather than oxygen, from the medium. A second type of bicarbonate effect on photo-inhibition, in apparent contradiction to the protective effect of added NaHCO3, is that thylakoid membranes that were depleted in their endogenous bicarbonate by treatment with formate were found to be less susceptible to photo-inhibition than thylakoids in the normal non-depleted state.
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Affiliation(s)
- C Sundby
- Dept. of Biochemistry, University of Lund, Sweden
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12
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Changes in the photosynthetic apparatus of red algae induced by spectral alteration of the light field. II. Further characterization of the light-dependent regulation of the apparent quantum yield of PS I. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1990. [DOI: 10.1016/0005-2728(90)90015-v] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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13
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Sundby C, Larsson UK, Henrysson T. Effects of bicarbonate on thylakoid protein phosphorylation. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1989. [DOI: 10.1016/s0005-2728(89)80259-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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14
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Mauzerall D, Greenbaum NL. The absolute size of a photosynthetic unit. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1989. [DOI: 10.1016/s0005-2728(89)80365-2] [Citation(s) in RCA: 112] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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15
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Rehm A, Gülzow M, Ried A. Changes in the photosynthetic apparatus of red algae induced by spectral alteration of the light field I. A decrease in the apparent quantum yield of PS I caused by preillumination with light 1. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1989. [DOI: 10.1016/s0005-2728(89)80413-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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16
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Coughlan S, Kieleczawa J, Hind G. Further enzymatic characteristics of a thylakoid protein kinase. J Biol Chem 1988. [DOI: 10.1016/s0021-9258(18)37437-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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17
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Packham NK. Is the 9 kDa thylakoid membrane phosphoprotein functionally and structurally analogous to the 'H' subunit of bacterial reaction centres? FEBS Lett 1988; 231:284-90. [PMID: 3282925 DOI: 10.1016/0014-5793(88)80835-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Although the amino acid sequence of the 9 kDa (phospho)protein of chloroplasts has been determined, the function of this thylakoid membrane protein in photosynthetic electron transport and the reason for its physiological control remains unclear. In this paper, I briefly review the evidence which indicates that the phosphorylation of the 9 kDa protein results in a partial inhibition of photosynthetic oxygen evolution by increasing the stability of the semiquinone bound to QA the primary, plastoquinone-binding site of photosystem II (PS II). I propose that in its dephosphorylated state, the 9 kDa thylakoid membrane protein may serve PS II to ensure efficient photochemical charge separation by aiding the transfer of reducing equivalents out of the reaction centre to the attendant plastoquinone pool. This function is analogous to that proposed for the H-subunit of the reaction centre of photosynthetic eubacteria. Whether these two proteins have evolved from a common ancestral reaction centre protein is discussed in the light of a comparison of their amino acid sequences and predicted secondary structures.
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Affiliation(s)
- N K Packham
- Department of Biochemistry, The University, Newcastle-upon-Tyne, England
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18
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Allen JF, Melis A. The rate of P-700 photooxidation under continuous illumination is independent of State 1-State 2 transitions in the green alga Scenedesmus obliquus. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1988. [DOI: 10.1016/0005-2728(88)90059-x] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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19
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Packham NK, Hodges M, Etienne AL, Briantais JM. Changes in the flash-induced oxygen yield pattern by thylakoid membrane phosphorylation. PHOTOSYNTHESIS RESEARCH 1988; 15:221-232. [PMID: 24430924 DOI: 10.1007/bf00047354] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/1987] [Accepted: 10/16/1987] [Indexed: 06/03/2023]
Abstract
Phosphorylation of thylakoid membrane proteins results in a partial inhibition (approximately 15-20%) of the light-saturated rate of oxygen evolution. The site of inhibition is thought to be located on the acceptor side of photosystem 2 (PS2) between the primary, QA, and secondary, QB, plastoquinone acceptors (Hodges et al. 1985, 1987). In this paper we report that thylakoid membrane phosphorylation increases the damping of the quaternary oscillation in the flash oxygen yield and increases the extent of the fast component in the deactivation of the S2 oxidation state. These results support the proposal that thylakoid membrane protein phosphorylation decreases the equilibrium constant for the exchange of an electron between QA and QB. An analysis of the oxygen release patterns using the recurrence matrix model of Lavorel (1976) indicates that thylakoid membrane phosphorylation increases the probability that PS2 miss a S-state transition by 20%. This is equivalent, however, to an insignificant inhibition (approximately 2.4%) of the light-saturated oxygen evolution rate. If a double miss in the S-state transitions is included when the PS2 centres are in S2 the fit between the experimental and theoretical oxygen yield sequences is better, and sufficient to account for the 15-20% inhibition in the steady-state oxygen yield. A double miss in the S-state transition is a consequence of an increased population of PS2 centres retaining QA (-): not only will these PS2 centres fail to catalyse photochemical charge transfer until QA (-) is reoxidized, but the re-oxidation reaction will also result in the deactivation of S2 to S1.
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Affiliation(s)
- N K Packham
- Laboratorie de photosynthese, CNRS, 91190, Gif-sur-Yvette, France
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20
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Marder JB, Telfer A, Barber J. The D1 polypeptide subunit of the Photosystem II reaction centre has a phosphorylation site at its amino terminus. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1988. [DOI: 10.1016/0005-2728(88)90172-7] [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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21
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Hodges M, Boussac A, Briantais JM. Thylakoid membrane protein phosphorylation modifies the equilibrium between Photosystem II quinone electron acceptors. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1987. [DOI: 10.1016/0005-2728(87)90183-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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22
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Phosphorylation of the 9 kDa Photosystem II-associated protein and the inhibition of photosynthetic electron transport. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1987. [DOI: 10.1016/0005-2728(87)90047-8] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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23
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Williams WP, Allen JF. State 1/State 2 changes in higher plants and algae. PHOTOSYNTHESIS RESEARCH 1987; 13:19-45. [PMID: 24435719 DOI: 10.1007/bf00032263] [Citation(s) in RCA: 96] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/1986] [Accepted: 01/21/1987] [Indexed: 06/03/2023]
Abstract
Current ideas regarding the molecular basis of State 1/State 2 transitions in higher plants and green algae are mainly centered around the view that excitation energy distribution is controlled by phosphorylation of the light-harvesting complex of photosystem II (LHC-II). The evidence supporting this view is examined and the relationship of the transitions occurring in these systems to the corresponding transitions seen in red and blue-green algae is explored.
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Affiliation(s)
- W P Williams
- Department of Biochemistry, King's College London (KQC), Kensington Campus, Campden Hill, W8 7AH, London
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24
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25
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Jennings RC, Zucchelli G. Studies on thylakoid phosphorylation and noncyclic electron transport. Arch Biochem Biophys 1986; 246:108-13. [PMID: 3516071 DOI: 10.1016/0003-9861(86)90454-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The effect of thylakoid phosphorylation on noncyclic electron transport in spinach chloroplasts was investigated by measuring both the reduction of nicotinamide adenine dinucleotide phosphate (NADP) and the steady-state redox level of the primary electron acceptor quinone of photosystem II (Q) during electron flow to NADP. These data are compared with the theoretical predictions for an electron transport model which relates both the redox levels of Q and the photosystem II optical cross section to the overall velocity of noncyclic electron flow. It is demonstrated that transfer of 15-20% of the photosystem II antenna to photosystem I may stimulate electron flow to NADP only if Q is less than 60-70% oxidized (this condition exists with our thylakoids, even at extremely low absorption fluxes, when the illumination is not specifically enriched in photosystem I absorbed wavelengths); in phosphorylated thylakoids the steady-state redox level Q is substantially shifted to a more oxidized one (measurements of this parameter using light of different wavelengths quantitatively support the idea that thylakoid phosphorylation leads to increased photosystem I and decreased photosystem II cross sections); thylakoid phosphorylation leads to stimulated noncyclic electron flow to NADP only when the increased photosystem I antenna is able to bring about large increases in the steady-state level of oxidized Q.
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26
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Black MT, Brearley TH, Horton P. Heterogeneity in chloroplast photosystem II. PHOTOSYNTHESIS RESEARCH 1986; 8:193-207. [PMID: 24443258 DOI: 10.1007/bf00037128] [Citation(s) in RCA: 61] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/1985] [Revised: 07/01/1985] [Accepted: 07/15/1985] [Indexed: 06/03/2023]
Abstract
Photosystem-two (PSII) in the chloroplasts of higher plants and green algae is not homogeneous. A review of PSII heterogeneity is presented and a model is proposed which is consistent with much of the data presented in the literature. It is proposed that the non-quinone electron acceptor of PSII is preferentially associated with the sub-population of PSII known as PSIIß.
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Affiliation(s)
- M T Black
- Research Institute for Photosynthesis, University of Sheffield, S10 2TN, Sheffield, UK
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27
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Barber J. Regulation of energy transfer by cations and protein phosphorylation in relation to thylakoid membrane organisation. PHOTOSYNTHESIS RESEARCH 1986; 10:243-253. [PMID: 24435371 DOI: 10.1007/bf00118289] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
A brief review is given of the state of knowledge which indicates that the State I-State II transition in higher plants and green algae is due to the reversible phosphorylation of the chlorophyll a/b light harvesting complex. The importance of membrane reorganisational changes in this process is discussed in terms of changes in electrostatic parameters as emphasised by the interplay of the effect of phosphorylation and the background levels of cations surrounding the membrane. It is argued that recognition of this interplay is vital when using the bipartite or tripartite models of Butler to obtain quantitative information of energy transfer between the various pigment complexes.
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Affiliation(s)
- J Barber
- Department of Pure and Applied Biology, Imperial College of Science and Technology, Prince Consort Road, SW7 2BB, London, UK
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28
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Horton P, Lee P. Phosphorylation of chloroplast membrane proteins partially protects against photoinhibition. PLANTA 1985; 165:37-42. [PMID: 24240955 DOI: 10.1007/bf00392209] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/1984] [Accepted: 12/20/1984] [Indexed: 06/02/2023]
Abstract
Thylakoids isolated from peas (Pisum sativum cv. Kelvedon Wonder) and phosphorylated by incubation with ATP have been compared with non-phosphorylated thylakoids in their sensitivity to photoinhibition by exposure to illumination in vitro. Assays of the kinetics of fluorescence induction at 20° C and the fluorescence emission spectra at-196° C indicate a proportionally larger decrease in fluorescence as a result of photoinhibitory treatment of non-phosphorylated compared with phosphorylated thylakoids. It is concluded that protein phosphorylation can afford partial protection to thylakoids exposed to photoinhibitory conditions.
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Affiliation(s)
- P Horton
- Research Institute for Photosynthesis, University of Sheffield, S10 2TN, Sheffield, UK
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