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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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Related in: MedlinePlus

Overlap of the structural models of LHCII (Liu et al. 2004) and CP29 ((Pan et al. 2011)). aSide view (from within the membrane) on the protein backbone of LHCII (red) and CP29 (yellow) and the xanthophylls of LHCII (light blue) and CP29 (dark blue). Main differences are the lack of the N-terminal part of CP29 which apparently was cleaved off during crystallization and the lack of VX in CP29. For the rest, both proteins show very similar structures. bTop view showing that the Chl organization in LHCII (red) and CP29 (yellow) is rather similar although not identical
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Fig4: Overlap of the structural models of LHCII (Liu et al. 2004) and CP29 ((Pan et al. 2011)). aSide view (from within the membrane) on the protein backbone of LHCII (red) and CP29 (yellow) and the xanthophylls of LHCII (light blue) and CP29 (dark blue). Main differences are the lack of the N-terminal part of CP29 which apparently was cleaved off during crystallization and the lack of VX in CP29. For the rest, both proteins show very similar structures. bTop view showing that the Chl organization in LHCII (red) and CP29 (yellow) is rather similar although not identical

Mentions: The antenna complexes of PSII from higher plants are composed of members of the Lhc multigenic family. The structure of a monomeric subunit of trimeric LHCII (Liu et al. 2004; Standfuss et al. 2005) is given in Fig 4. Each monomer coordinates eight Chls a, six Chls b and four xanthophylls (one Nx, two Lut’s and one Vx). The two Lut’s are located at sites L1 and L2 in the center of the molecule while Nx and Vx are located at the periphery in sites N1 and V1, respectively (Croce et al. 1999; Caffarri et al. 2001; Ruban and Horton 1999). The average distance between the Chls is around 10 Å, which leads to excitonic interactions between the pigments, resulting in fast energy transfer within the complex.Fig. 4


Light harvesting in photosystem II.

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

Overlap of the structural models of LHCII (Liu et al. 2004) and CP29 ((Pan et al. 2011)). aSide view (from within the membrane) on the protein backbone of LHCII (red) and CP29 (yellow) and the xanthophylls of LHCII (light blue) and CP29 (dark blue). Main differences are the lack of the N-terminal part of CP29 which apparently was cleaved off during crystallization and the lack of VX in CP29. For the rest, both proteins show very similar structures. bTop view showing that the Chl organization in LHCII (red) and CP29 (yellow) is rather similar although not identical
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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

Fig4: Overlap of the structural models of LHCII (Liu et al. 2004) and CP29 ((Pan et al. 2011)). aSide view (from within the membrane) on the protein backbone of LHCII (red) and CP29 (yellow) and the xanthophylls of LHCII (light blue) and CP29 (dark blue). Main differences are the lack of the N-terminal part of CP29 which apparently was cleaved off during crystallization and the lack of VX in CP29. For the rest, both proteins show very similar structures. bTop view showing that the Chl organization in LHCII (red) and CP29 (yellow) is rather similar although not identical
Mentions: The antenna complexes of PSII from higher plants are composed of members of the Lhc multigenic family. The structure of a monomeric subunit of trimeric LHCII (Liu et al. 2004; Standfuss et al. 2005) is given in Fig 4. Each monomer coordinates eight Chls a, six Chls b and four xanthophylls (one Nx, two Lut’s and one Vx). The two Lut’s are located at sites L1 and L2 in the center of the molecule while Nx and Vx are located at the periphery in sites N1 and V1, respectively (Croce et al. 1999; Caffarri et al. 2001; Ruban and Horton 1999). The average distance between the Chls is around 10 Å, which leads to excitonic interactions between the pigments, resulting in fast energy transfer within the complex.Fig. 4

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