Functional architecture of higher plant photosystem II supercomplexes. EMBO J

Faculté des Sciences Luminy, Laboratoire de Génétique et Biophysique des Plantes, Université Aix Marseille, Marseille, France.
The EMBO Journal (Impact Factor: 10.75). 09/2009; 28(19):3052-63. DOI: 10.1038/emboj.2009.232
Source: PubMed

ABSTRACT Photosystem II (PSII) is a large multiprotein complex, which catalyses water splitting and plastoquinone reduction necessary to transform sunlight into chemical energy. Detailed functional and structural studies of the complex from higher plants have been hampered by the impossibility to purify it to homogeneity. In this work, homogeneous preparations ranging from a newly identified particle composed by a monomeric core and antenna proteins to the largest C(2)S(2)M(2) supercomplex were isolated. Characterization by biochemical methods and single particle electron microscopy allowed to relate for the first time the supramolecular organization to the protein content. A projection map of C(2)S(2)M(2) at 12 A resolution was obtained, which allowed determining the location and the orientation of the antenna proteins. Comparison of the supercomplexes obtained from WT and Lhcb-deficient plants reveals the importance of the individual subunits for the supramolecular organization. The functional implications of these findings are discussed and allow redefining previous suggestions on PSII energy transfer, assembly, photoinhibition, state transition and non-photochemical quenching.

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Available from: Roberta Croce, Sep 02, 2015
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    • "Mass spectrometric analyses of isolated C 2 S 2 M 2 PSII supercomplexes revealed the presence of extrinsic subunits PSBP, PSBQ, and PSBR, while PSBS was not identified, suggesting that PSBS does not influence the association of the PSII core with the outer light-harvesting complex system (Pagliano et al., 2014). In line with the proteomic findings, recent data suggest that subunits PSBP, PSBQ, and PSBR contribute to the stability of PSII-LHCII supercomplexes in vascular plants (Caffarri et al., 2009; Ifuku et al., 2011; Allahverdiyeva et al., 2013). A recent quantitative proteomic study performed with C. reinhardtii identified PSBR as the only PSII subunit to be induced upon the shift from photoheterotrophic to photoautotrophic growth conditions similar to LHCSR3 (Höhner et al., 2013). "
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    ABSTRACT: In Chlamydomonas reinhardtii the LHCSR3 protein is crucial for efficient energy-dependent thermal dissipation of excess absorbed light energy and functionally associates with PSII-LHCII supercomplexes. Currently, it is unknown of how LHCSR3 binds to the PSII-LHCII supercomplex. In this study we investigated the role of PSBR, an intrinsic membrane-spanning PSII subunit, in binding of LHCSR3 to PSII-LHCII supercomplexes. Down regulation of PSBR expression diminished the efficiency of oxygen evolution and the extent of non-photochemical quenching (NPQ) and had an impact on the stability of the oxygen-evolving complex as well as on PSII-LHCII-LHCSR3 supercomplex formation. Its down regulation destabilized the PSII-LHCII supercomplex and strongly reduced binding of LHCSR3 to PSII-LHCII supercomplexes as revealed by quantitative proteomics. PSBP deletion on the contrary destabilized PSBQ binding but did not affect PSBR and LHCSR3 association with PSII-LHCII. In summary, the data provide clear evidence that PSBR is required for stable binding of LHCSR3 to PSII-LHCII supercomplexes, essential for efficient qE quenching, and integrity of the PSII-LHCII-LHCSR3 supercomplex under continuous high light. Copyright © 2015, Plant Physiology.
    Plant physiology 02/2015; 167(4). DOI:10.1104/pp.15.00094 · 7.39 Impact Factor
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    • "We aim to investigate the long-range transport of excitation energy in the Photosystem II supercomplex, from the surrounding antenna complexes, through the outer components of the supercomplex, to the reaction center – by means of a full quantum simulation. To this end, we model a subsection of the Photosystem II supercomplex originally isolated by Croce, et al. [24] and subsequently used as a foundation for a structure based excitation energy transport model to explain the measured fluorescence lifetimes [2]. Figure 1 shows the largest PSII supercomplex previously modeled [2] [16]. The colored pigments in LHCII, CP43, and the reaction center shown in Figure 1 represent the subsystem that we model in this work: it contains 33 chromophores distributed between a LHCII monomer (14 pigments), CP43 (13 pigments), and a truncated reation center (6 pigments). "
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    ABSTRACT: We simulate the long-range inter-complex electronic energy transfer in Photosystem II -- from the antenna complex, via a core complex, to the reaction center -- using a non-Markovian (ZOFE) quantum master equation description that allows us to quantify the electronic coherence involved in the energy transfer. We identify the pathways of the energy transfer in the network of coupled chromophores, using a description based on excitation probability currents. We investigate how the energy transfer depends on the initial excitation -- localized, coherent initial excitation versus delocalized, incoherent initial excitation -- and find that the energy transfer is remarkably robust with respect to such strong variations of the initial condition. To explore the importance of vibrationally enhanced transfer and to address the question of optimization in the system parameters, we vary the strength of the coupling between the electronic and the vibrational degrees of freedom. We find that the original parameters lie in a (broad) region that enables optimal transfer efficiency, and that the energy transfer appears to be very robust with respect to variations in the vibronic coupling. Nevertheless, vibrationally enhanced transfer appears to be crucial to obtain a high transfer efficiency. We compare our quantum simulation to a "classical" rate equation based on a modified-Redfield/generalized-F\"orster description that was previously used to simulate energy transfer dynamics in the entire Photosystem II complex, and find very good agreement between quantum and rate-equation simulation of the overall energy transfer dynamics.
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    • "The diameter of grana is typically 300–600 nm and the extent of grana membrane stacking is dynamically regulated based on the prevailing light environment. In short, shade plants contain broader grana stacks with more membrane layers per granum as compared to sun plants [25].Electron microcopy has revealed that in spinach (Spinacia oleracea)a10min switch to a lower light intensity increased grana size and number per chloroplast by 10–20% and returning of the leaves to the normal growth light for 10 min reversed the phenomenon [26].T h eP S I I complexes are most active as dimers and supercomplexes [27], which are densely packed in grana core regions of the thylakoid membrane network [28] [29] [30]. However, monomerization and migration of PSII complexes to non-appressed thylakoids are a prerequisite for the repair cycle [31]. "
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    ABSTRACT: Photosystem (PS) II is a multisubunit thylakoid membrane pigment-protein complex responsible for light-driven oxidation of water and reduction of plastoquinone. Currently more than 40 proteins are known to associate with PSII, either stably or transiently. The inherent feature of the PSII complex is its vulnerability in light, with the damage mainly targeted to one of its core proteins, the D1 protein. The repair of the damaged D1 protein, i.e. the repair cycle of PSII, initiates in the grana stacks where the damage generally takes place, but subsequently continues in non-appressed thylakoid domains, where many steps are common for both the repair and de novo assembly of PSII. The sequence of the (re)assembly steps of genuine PSII subunits is relatively well-characterized in higher plants. A number of novel findings have shed light into the regulation mechanisms of lateral migration of PSII subcomplexes and the repair as well as the (re)assembly of the complex. Beside the utmost importance of the PSII repair cycle for the maintenance of PSII functionality, recent research has pointed out that the maintenance of PSI is closely dependent on regulation of the PSII repair cycle. This review focuses on the current knowledge of regulation of the repair cycle of PSII in higher plant chloroplasts. Particular emphasis is paid on sequential assembly steps of PSII and the function of the number of PSII auxiliary proteins involved both in the biogenesis and repair of PSII. This article is part of a Special Issue entitled: Chloroplast Biogenesis. Copyright © 2015. Published by Elsevier B.V.
    Biochimica et Biophysica Acta (BBA) - Bioenergetics 01/2015; 57(9). DOI:10.1016/j.bbabio.2015.01.006 · 4.83 Impact Factor
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