Chloroplast protein phosphorylation couples plastoquinone redox state to distribution of excitation energy between photosystems

Allen, John F.; Bennett, John; Steinback, Katherine E.; Arntzen, Charles J.

doi:10.1038/291025a0

Cited by 618 publications

(314 citation statements)

References 32 publications

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“…It is mainly associated with Photosystem II (PS II) and functions as an efficient light collector for the reaction center, where excitations lead to charge separation (van Amerongen and Dekker 2003;. Over the past few years a deeper knowledge about its function has been obtained, namely: (i) the absorption of sunlight energy and the efficient transfer to the core of PS II (van Amerongen and Dekker 2003;, (ii) the participation in the regulation of the light-energy distribution between Photosystems I and II in plants (Allen et al 1981), (iii) the participation in the dissipation of excess excitation energy (Jennings et al 1991) and (iv) the stacking of the grana (Ke 2001). Because LHC II is a mixture of several isoforms referred to as proteins, Lhcb1, Lhcb2, and Lhcb3, one might wonder whether every individual protein component of LHC II has associated a unique functional property to it, which is strongly suggested by the fact that there are more similarities between the same isoforms belonging to distinct species than between two isoforms of the same plant species (Jansson 1994;Standfuss and Ku¨hlbrandt 2004).…”

Section: Introductionmentioning

confidence: 99%

A comparison of the three isoforms of the light-harvesting complex II using transient absorption and time-resolved fluorescence measurements

et al. 2006

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In this article we report the characterization of the energy transfer process in the reconstituted isoforms of the plant light-harvesting complex II. Homotrimers of recombinant Lhcb1 and Lhcb2 and monomers of Lhcb3 were compared to native trimeric complexes. We used low-intensity femtosecond transient absorption (TA) and time-resolved fluorescence measurements at 77 K and at room temperature, respectively, to excite the complexes selectively in the chlorophyll b absorption band at 650 nm with 80 fs pulses and on the high-energy side of the chlorophyll a absorption band at 662 nm with 180 fs pulses. The subsequent kinetics was probed at 30-35 different wavelengths in the region from 635 to 700 nm. The rate constants for energy transfer were very similar, indicating that structurally the three isoforms are highly homologous and that probably none of them play a more significant role in light-harvesting and energy transfer. No signature has been found in the transient absorption measurements at 77 K for Lhcb3 which might suggest that this protein acts as a relative energy sink of the excitations in heterotrimers of Lhcb1/Lhcb2/Lhcb3. Minor differences in the amplitudes of some of the rate constants and in the absorption and fluorescence properties of some pigments were observed, which are ascribed to slight variations in the environment surrounding some of the chromophores depending on the isoform. The decay of the fluorescence was also similar for the three isoforms and multi-exponential, characterized by two major components in the ns regime and a minor one in the ps regime. In agreement with previous transient absorption measurements on native LHC II complexes, Chl b fi Chl a energy transfer exhibited very fast channels but at the same time a slow component (ps). The Chls absorbing at around 660 nm exhibited both fast energy transfer which we ascribe to transfer from 'red' Chl b towards 'red' Chl a and slow transfer from 'blue' Chl a towards 'red' Chl a. The results are discussed in the context of the new available atomic models for LHC II.

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Section: Introductionmentioning

confidence: 99%

A comparison of the three isoforms of the light-harvesting complex II using transient absorption and time-resolved fluorescence measurements

et al. 2006

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“…The reversible phosphorylation of LHC II is thought to regulate the distribution of excitation energy between PS II and PS I, and thereby permit the chloroplast to maximise the overall efficiency of photosynthesis under any given light condition [2,3]. The molecular mechanism of this control process may involve the lateral migration of phospho-LHC II from the PS II-enriched appressed membranes of the granal stacks to the PS I-enriched nonappressed granal end-membranes and stromal lamellae (see [4]).…”

Section: Thylakoid Membrane Protein Phosphorylation Regulates the Dismentioning

confidence: 99%

Is the 9 kDa thylakoid membrane phosphoprotein functionally and structurally analogous to the ‘H’ subunit of bacterial reaction centres?

Packham

1988

FEBS Letters

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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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“…In studies of regulation of thylakoid protein phosphorylation it is usually assumed that the kinase is under redox control, while the phosphatase is constitutively active at a constant low level [3]. However, the converse could also be true, since activation of the phos- Abbreviations: PSI, photosystem I; PSII, photosystem II; LHCII, light harvesting complex II; SDS-PAGE, sodium dodecyl sulfate-polyacrylamide gel electrophoresis; CP43, 43 kDa PSII light harvesting core protein; D 1 and D2, 31 and 32 kDa PSII reaction center polypeptides.…”

Section: Introductionmentioning

confidence: 99%

Chloroplast thylakoid protein phosphatase reactions are redox‐independent and kinetically heterogeneous

1993

Self Cite

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At least eleven thylakoid proteins become phosphorylated under reducing conditions, and redox titration has identified a common midpoint potential of Ern = +38 + 4 mV, n = 0.95 + 0.06. In the presence of the phosphatase inhibitor NaF (10 mM), the redox dependency of phosphorylation is found to be essentially unchanged: E m = +50 + 3 mV, n = 1.02 + 0.04. Thylakoid membranes were phosphorylated in the light and then incubated at various redox potentials for 15 min in the dark; no redox dependency was observed in the dephosphorylation of any of the 17 bands then distinguishable by autoradiography and phosphorimaging. The phosphoprotein phosphatase reactions can be divided arbitrarily into four kinetic classes: the fastest, class I, includes LHC II; the moderate class II includes D1 and D2; the slow class III includes CP43 and the 9 kDa phosphoprotein; finally, a 19.5 kDa protein exhibited no loss of 32P at all. In separate experiments we measured thylakoid protein dephosphorylation initiated by changing the redox potential from -140 to +200 mV, in the presence or absence of fluoride. In this case the results are consistent with at least two kinetically distinguishable classes of phosphoprotein phosphatase reactions. We conclude that thylakoid protein phosphatase reactions are kinetically heterogeneous and redox-independent. It follows that the redox dependency of thylakoid protein phosphorylation is a property of thylakoid protein kinase reactions. Our observed E m and n values are consistent with a primary site of kinase redox control at the level of PQ/PQ'-of the Q~ (Q,) site of the cytochrome b6lfcomplex.

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Chloroplast protein phosphorylation couples plastoquinone redox state to distribution of excitation energy between photosystems

Cited by 618 publications

References 32 publications

A comparison of the three isoforms of the light-harvesting complex II using transient absorption and time-resolved fluorescence measurements

A comparison of the three isoforms of the light-harvesting complex II using transient absorption and time-resolved fluorescence measurements

Is the 9 kDa thylakoid membrane phosphoprotein functionally and structurally analogous to the ‘H’ subunit of bacterial reaction centres?

Chloroplast thylakoid protein phosphatase reactions are redox‐independent and kinetically heterogeneous

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