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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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Chlorophyll organization in the core complex of PSII (Guskov et al. 2009). Chls P, red; Chls D1 and D2, orange; Chls z green; Pheos, yellow. The Chls of CP47 are in blue and those of CP43 in cyan. The phytol chains of the Chls are omitted for clarity. The upper figure shows a top view (from the stroma) and the lower figure provides a side view
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Fig1: Chlorophyll organization in the core complex of PSII (Guskov et al. 2009). Chls P, red; Chls D1 and D2, orange; Chls z green; Pheos, yellow. The Chls of CP47 are in blue and those of CP43 in cyan. The phytol chains of the Chls are omitted for clarity. The upper figure shows a top view (from the stroma) and the lower figure provides a side view

Mentions: The RC of PSII itself only contains six chlorophylls a (Chls a) and two pheophytins but it is always present in the so-called core complex that also contains the pigment-proteins CP43 and CP47, providing additional 13 and 16 Chls a, respectively, together with several β-carotene molecules (see (Umena et al. 2011) for the most recent PSII core structure). Both antenna complexes feed excitation energy into the RC. These antenna Chls are on the one hand at a “safe” distance from the RC pigments, which are highly oxidizing after charge separation (see Fig. 1), preventing direct pigment oxidation in the antenna, and on the other hand close enough to perform efficient excitation energy transfer (EET).Fig. 1


Light harvesting in photosystem II.

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

Chlorophyll organization in the core complex of PSII (Guskov et al. 2009). Chls P, red; Chls D1 and D2, orange; Chls z green; Pheos, yellow. The Chls of CP47 are in blue and those of CP43 in cyan. The phytol chains of the Chls are omitted for clarity. The upper figure shows a top view (from the stroma) and the lower figure provides a side view
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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

Fig1: Chlorophyll organization in the core complex of PSII (Guskov et al. 2009). Chls P, red; Chls D1 and D2, orange; Chls z green; Pheos, yellow. The Chls of CP47 are in blue and those of CP43 in cyan. The phytol chains of the Chls are omitted for clarity. The upper figure shows a top view (from the stroma) and the lower figure provides a side view
Mentions: The RC of PSII itself only contains six chlorophylls a (Chls a) and two pheophytins but it is always present in the so-called core complex that also contains the pigment-proteins CP43 and CP47, providing additional 13 and 16 Chls a, respectively, together with several β-carotene molecules (see (Umena et al. 2011) for the most recent PSII core structure). Both antenna complexes feed excitation energy into the RC. These antenna Chls are on the one hand at a “safe” distance from the RC pigments, which are highly oxidizing after charge separation (see Fig. 1), preventing direct pigment oxidation in the antenna, and on the other hand close enough to perform efficient excitation energy transfer (EET).Fig. 1

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