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Light harvesting in photosystem II.

van Amerongen H, Croce R - Photosyn. Res. (2013)

Bottom Line: The whole system consists of many subunits and appears to be modular, i.e., both its composition and organization depend on environmental conditions, especially on the quality and intensity of the light.It will become clear that time-resolved fluorescence data can provide invaluable information about the organization and functioning of thylakoid membranes.At the end, an overview will be given of unanswered questions that should be addressed in the near future.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Biophysics, Wageningen University, P. O. Box 8128, 6700 ET, Wageningen, The Netherlands, herbert.vanamerongen@wur.nl.

ABSTRACT
Water oxidation in photosynthesis takes place in photosystem II (PSII). This photosystem is built around a reaction center (RC) where sunlight-induced charge separation occurs. This RC consists of various polypeptides that bind only a few chromophores or pigments, next to several other cofactors. It can handle far more photons than the ones absorbed by its own pigments and therefore, additional excitations are provided by the surrounding light-harvesting complexes or antennae. The RC is located in the PSII core that also contains the inner light-harvesting complexes CP43 and CP47, harboring 13 and 16 chlorophyll pigments, respectively. The core is surrounded by outer light-harvesting complexes (Lhcs), together forming the so-called supercomplexes, at least in plants. These PSII supercomplexes are complemented by some "extra" Lhcs, but their exact location in the thylakoid membrane is unknown. The whole system consists of many subunits and appears to be modular, i.e., both its composition and organization depend on environmental conditions, especially on the quality and intensity of the light. In this review, we will provide a short overview of the relation between the structure and organization of pigment-protein complexes in PSII, ranging from individual complexes to entire membranes and experimental and theoretical results on excitation energy transfer and charge separation. It will become clear that time-resolved fluorescence data can provide invaluable information about the organization and functioning of thylakoid membranes. At the end, an overview will be given of unanswered questions that should be addressed in the near future.

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Model of the PSII supercomplex C2S2M2 from higher plants. Top-view for the stromal side on a C2S2M2 supercomplex from A. thaliana. Based on the projection map of C2S2M2 at 12 Å resolution, a model of the 3D structure of the supercomplex was reconstructed (Caffarri et al. 2009) using the crystal structures of PSII core (Guskov et al. 2009) and LHCII (Liu et al. 2004). For the minor antenna complexes, the structure of a monomer of LHCII was used while the pigment composition/occupancy was assigned based on the results of mutation analysis experiments on in vitro reconstituted complexes (Bassi et al. 1999; Remelli et al. 1999; Ballottari et al. 2009; Passarini et al. 2009)
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Fig2: Model of the PSII supercomplex C2S2M2 from higher plants. Top-view for the stromal side on a C2S2M2 supercomplex from A. thaliana. Based on the projection map of C2S2M2 at 12 Å resolution, a model of the 3D structure of the supercomplex was reconstructed (Caffarri et al. 2009) using the crystal structures of PSII core (Guskov et al. 2009) and LHCII (Liu et al. 2004). For the minor antenna complexes, the structure of a monomer of LHCII was used while the pigment composition/occupancy was assigned based on the results of mutation analysis experiments on in vitro reconstituted complexes (Bassi et al. 1999; Remelli et al. 1999; Ballottari et al. 2009; Passarini et al. 2009)

Mentions: In Fig. 2, a model of a plant PSII supercomplex is shown. It is composed of a PSII core together with the gene products of genes Lhcb1-6 in a well-defined arrangement. The largest supercomplexes contain a dimeric core, four LHCII (encoded by Lhcb1-3) trimers, two strongly bound (S) and two moderately strongly bound (M), and two monomeric copies each of CP29 (Lhcb4), CP26 (Lhcb5), and CP24 (Lhcb6). Supercomplexes of different sizes can be isolated (Caffarri et al. 2009), which is probably partly due to the solubilization process but it is also known that a sub-population of smaller supercomplexes is also observed in high light plants (see e.g., (Daum et al. 2010; Kouril et al. 2012)).Fig. 2


Light harvesting in photosystem II.

van Amerongen H, Croce R - Photosyn. Res. (2013)

Model of the PSII supercomplex C2S2M2 from higher plants. Top-view for the stromal side on a C2S2M2 supercomplex from A. thaliana. Based on the projection map of C2S2M2 at 12 Å resolution, a model of the 3D structure of the supercomplex was reconstructed (Caffarri et al. 2009) using the crystal structures of PSII core (Guskov et al. 2009) and LHCII (Liu et al. 2004). For the minor antenna complexes, the structure of a monomer of LHCII was used while the pigment composition/occupancy was assigned based on the results of mutation analysis experiments on in vitro reconstituted complexes (Bassi et al. 1999; Remelli et al. 1999; Ballottari et al. 2009; Passarini et al. 2009)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3824292&req=5

Fig2: Model of the PSII supercomplex C2S2M2 from higher plants. Top-view for the stromal side on a C2S2M2 supercomplex from A. thaliana. Based on the projection map of C2S2M2 at 12 Å resolution, a model of the 3D structure of the supercomplex was reconstructed (Caffarri et al. 2009) using the crystal structures of PSII core (Guskov et al. 2009) and LHCII (Liu et al. 2004). For the minor antenna complexes, the structure of a monomer of LHCII was used while the pigment composition/occupancy was assigned based on the results of mutation analysis experiments on in vitro reconstituted complexes (Bassi et al. 1999; Remelli et al. 1999; Ballottari et al. 2009; Passarini et al. 2009)
Mentions: In Fig. 2, a model of a plant PSII supercomplex is shown. It is composed of a PSII core together with the gene products of genes Lhcb1-6 in a well-defined arrangement. The largest supercomplexes contain a dimeric core, four LHCII (encoded by Lhcb1-3) trimers, two strongly bound (S) and two moderately strongly bound (M), and two monomeric copies each of CP29 (Lhcb4), CP26 (Lhcb5), and CP24 (Lhcb6). Supercomplexes of different sizes can be isolated (Caffarri et al. 2009), which is probably partly due to the solubilization process but it is also known that a sub-population of smaller supercomplexes is also observed in high light plants (see e.g., (Daum et al. 2010; Kouril et al. 2012)).Fig. 2

Bottom Line: The whole system consists of many subunits and appears to be modular, i.e., both its composition and organization depend on environmental conditions, especially on the quality and intensity of the light.It will become clear that time-resolved fluorescence data can provide invaluable information about the organization and functioning of thylakoid membranes.At the end, an overview will be given of unanswered questions that should be addressed in the near future.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Biophysics, Wageningen University, P. O. Box 8128, 6700 ET, Wageningen, The Netherlands, herbert.vanamerongen@wur.nl.

ABSTRACT
Water oxidation in photosynthesis takes place in photosystem II (PSII). This photosystem is built around a reaction center (RC) where sunlight-induced charge separation occurs. This RC consists of various polypeptides that bind only a few chromophores or pigments, next to several other cofactors. It can handle far more photons than the ones absorbed by its own pigments and therefore, additional excitations are provided by the surrounding light-harvesting complexes or antennae. The RC is located in the PSII core that also contains the inner light-harvesting complexes CP43 and CP47, harboring 13 and 16 chlorophyll pigments, respectively. The core is surrounded by outer light-harvesting complexes (Lhcs), together forming the so-called supercomplexes, at least in plants. These PSII supercomplexes are complemented by some "extra" Lhcs, but their exact location in the thylakoid membrane is unknown. The whole system consists of many subunits and appears to be modular, i.e., both its composition and organization depend on environmental conditions, especially on the quality and intensity of the light. In this review, we will provide a short overview of the relation between the structure and organization of pigment-protein complexes in PSII, ranging from individual complexes to entire membranes and experimental and theoretical results on excitation energy transfer and charge separation. It will become clear that time-resolved fluorescence data can provide invaluable information about the organization and functioning of thylakoid membranes. At the end, an overview will be given of unanswered questions that should be addressed in the near future.

Show MeSH
Related in: MedlinePlus