Significance of molecular crowding in grana membranes of higher plants for light harvesting by photosystem II

Haferkamp, Silvia; Kirchhoff, Helmut

doi:10.1007/s11120-007-9253-2

Cited by 25 publications

(34 citation statements)

References 12 publications

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“…For studying the impact of different protein packing densities on Φ coupling , BBY membranes (BBY according to Berthold et al 29 ) were fused with liposomes to incorporate additional lipids as described before. 31 As unfused starting material, we used a BBY preparation that was heavily depleted in lipids. Lipid depletion is indicated by lipid analysis that showed a mol-lipid/mol-Chl ratio of only ∼0.5, i.e., significantly lower than the ratio of 1.3 measured for BBY in previous studies.…”

Section: ■ Resultsmentioning

confidence: 99%

Carotenoid–Chlorophyll Coupling and Fluorescence Quenching Correlate with Protein Packing Density in Grana-Thylakoids

et al. 2013

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ABSTRACT:The regulation of light-harvesting in photosynthesis under conditions of varying solar light irradiation is essential for the survival and fitness of plants and algae. It has been proposed that rearrangements of protein distribution in the stacked grana region of thylakoid membranes connected to changes in the electronic pigment-interaction play a key role for this regulation. In particular, carotenoid−chlorophyll interactions seem to be crucial for the downregulation of photosynthetic light-harvesting. So far, it has been difficult to determine the influence of the dense protein packing found in native photosynthetic membrane on these interactions. We investigated the changes of the electronic couplings between carotenoids and chlorophylls and the quenching in grana thylakoids of varying protein packing density by two-photon spectroscopy, conventional chlorophyll fluorometry, low-temperature fluorescence spectroscopy, and electron micrographs of freeze-fracture membranes. We observed an increasing carotenoid−chlorophyll coupling and fluorescence quenching with increasing packing density. Simultaneously, the antennas size and excitonic connectivity of Photosystem II increased with increasing quenching and carotenoid−chlorophyll coupling whereas isolated, decoupled LHCII trimers decreased. Two distinct quenching data regimes could be identified that show up at different protein packing densities. In the regime corresponding to higher protein packing densities, quenching is strongly correlated to carotenoid−chlorophyll interactions whereas in the second regime, a weak correlation is apparent with low protein packing densities. Native membranes are in the strong-coupling data regime. Consequently, PSII and LHCII in grana membranes of plants are already quenched by protein crowding. We concluded that this ensures efficient electronic connection of all pigment−protein complexes for intermolecular energy transfer to the reaction centers and allows simultaneously sensitive regulation of light harvesting by only small changes in the protein packaging. ■ INTRODUCTIONPhotosynthesis in higher plants and algae is initiated by the harvesting of sunlight through a series of pigment−protein complexes located in the thylakoid membranes of chloroplasts. Starting from these light harvesting complexes (LHCs), the absorbed energy is efficiently transferred from one complex to the other. These transfer processes end up in the photosystem reaction centers where the energy is converted into redox energy. However, plants are exposed to changing light intensities on a daily basis that can vary over several orders of magnitude. 1 Thus, a regulation mechanism is necessary that assures effective usage of sunlight energy under low-light conditions but avoids photo-oxidative damage to the reaction centers or other parts of the photosynthetic apparatus if the absorbed light exceeds its capacity. A main mechanism that evolved to minimize photo-oxidative damage in plants is called high-energy quenching (qE). qE enables the dissipation ...

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Section: ■ Resultsmentioning

confidence: 99%

Carotenoid–Chlorophyll Coupling and Fluorescence Quenching Correlate with Protein Packing Density in Grana-Thylakoids

et al. 2013

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“…Proteoliposomes, where light-harvesting complexes are embedded in a lipid bilayer that contains the lipids of the thylakoid membrane, are becoming a popular system to study antenna complexes in vitro (20,21,24,25,27,32,33). With the aim to mimic the thylakoid membrane, highly concentrated proteoliposomes with a lipid/protein molar ratio between ϳ30 -600:1 are used.…”

Section: Discussionmentioning

confidence: 99%

Light-harvesting Complexes (LHCs) Cluster Spontaneously in Membrane Environment Leading to Shortening of Their Excited State Lifetimes

Natali

Gruber

Dietzel

et al. 2016

Journal of Biological Chemistry

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The light reactions of photosynthesis, which include lightharvesting and charge separation, take place in the amphiphilic environment of the thylakoid membrane. The light-harvesting complex II (LHCII) is the main responsible for light absorption in plants and green algae and is involved in photoprotective mechanisms that regulate the amount of excited states in the membrane. The dual function of LHCII has been extensively studied in detergent micelles, but recent results have indicated that the properties of this complex differ in a lipid environment. In this work we checked these suggestions by studying LHCII in liposomes. By combining bulk and single molecule measurements, we monitored the fluorescence characteristics of liposomes containing single complexes up to densely packed proteoliposomes. We show that the natural lipid environment per se does not alter the properties of LHCII, which for single complexes remain very similar to that in detergent. However, we show that LHCII has the strong tendency to cluster in the membrane and that protein interactions and the extent of crowding modulate the lifetimes of the excited state in the membrane. Finally, the presence of LHCII monomers at low concentrations of complexes per liposome is discussed.Photosynthetic organisms evolved the capacity to harvest the energy of solar radiation and store it into chemical compounds. In vascular plants and green algae, sunlight is absorbed by a series of membrane proteins called light-harvesting complexes (LHC).3 The most abundant of these pigment-protein complexes is LHCII. The LHCs have a dual function; in low light conditions they absorb solar energy and efficiently transfer the excitation energy to the reaction center, and in high light they additionally play a role in photoprotection by dissipating the energy absorbed in excess as heat (1, 2). This last process called non-photochemical quenching (NPQ) leads to a decrease of the excited state lifetime of chlorophyll a (Chl a), limiting the possibility of Chl triplet formation and thus the production of singlet oxygen (3). The fast, on the timescale of seconds, and fully reversible part of NPQ is called qE. This mechanism is triggered by the acidification of the lumenal space of the thylakoids, which activates PsbS (4) and LhcSR (5), the proteins responsible for NPQ in plants and green algae, respectively, and the violaxanthin de-epoxidase, which converts violaxanthin into zeaxanthin (for reviews, see Refs. 6 and 7). Although the precise molecular mechanism of quenching has not been fully elucidated yet, a prominent idea discussed in literature is that NPQ is regulated via conformational changes of LHCII. Those changes could be correlated to, or even caused by, LHCII aggregation (8, 9). It was observed that low pH and zeaxanthin, both occurring in high light, enhance LHCII aggregation (10). Aggregation of LHCII in vitro is accompanied by a decrease of the Chl a fluorescence yield, indicating an increased rate of energy dissipation (9, 11). The generation of new quenching sit...

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“…The membranes are flat discs usually about 500 nm in diameter, reflecting the dimensions of grana membranes in vivo (Kirchhoff et al, 2004a). We used membranes either at their native protein density, or diluted by fusion with unilamellar liposomes containing the native lipid mixture (Haferkamp and Kirchhoff, 2008). Ficoll density gradient ultracentrifugation shows that the fused membranes have lower density than the original BBY particles (Haferkamp and Kirchhoff, 2008).…”

Section: Preparation Of Spinach Grana Membranesmentioning

confidence: 99%

“…We used membranes either at their native protein density, or diluted by fusion with unilamellar liposomes containing the native lipid mixture (Haferkamp and Kirchhoff, 2008). Ficoll density gradient ultracentrifugation shows that the fused membranes have lower density than the original BBY particles (Haferkamp and Kirchhoff, 2008). Gradual addition of liposomes in the fusion batch leads to a gradually decreased density of the BBY membranes (Haferkamp and Kirchhoff, 2008).…”

Section: Preparation Of Spinach Grana Membranesmentioning

confidence: 99%

Protein Diffusion and Macromolecular Crowding in Thylakoid Membranes

et al. 2008

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The photosynthetic light reactions of green plants are mediated by chlorophyll-binding protein complexes located in the thylakoid membranes within the chloroplasts. Thylakoid membranes have a complex structure, with lateral segregation of protein complexes into distinct membrane regions known as the grana and the stroma lamellae. It has long been clear that some protein complexes can diffuse between the grana and the stroma lamellae, and that this movement is important for processes including membrane biogenesis, regulation of light harvesting, and turnover and repair of the photosynthetic complexes. In the grana membranes, diffusion may be problematic because the protein complexes are very densely packed (approximately 75% area occupation) and semicrystalline protein arrays are often observed. To date, direct measurements of protein diffusion in green plant thylakoids have been lacking. We have developed a form of fluorescence recovery after photobleaching that allows direct measurement of the diffusion of chlorophyll-protein complexes in isolated grana membranes from Spinacia oleracea. We show that about 75% of fluorophores are immobile within our measuring period of a few minutes. We suggest that this immobility is due to a protein network covering a whole grana disc. However, the remaining fraction is surprisingly mobile (diffusion coefficient 4.6 6 0.4 3 10 211 cm 2 s 21 ), which suggests that it is associated with mobile proteins that exchange between the grana and stroma lamellae within a few seconds. Manipulation of the protein-lipid ratio and the ionic strength of the buffer reveals the roles of macromolecular crowding and protein-protein interactions in restricting the mobility of grana proteins.

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Significance of molecular crowding in grana membranes of higher plants for light harvesting by photosystem II

Cited by 25 publications

References 12 publications

Carotenoid–Chlorophyll Coupling and Fluorescence Quenching Correlate with Protein Packing Density in Grana-Thylakoids

Carotenoid–Chlorophyll Coupling and Fluorescence Quenching Correlate with Protein Packing Density in Grana-Thylakoids

Light-harvesting Complexes (LHCs) Cluster Spontaneously in Membrane Environment Leading to Shortening of Their Excited State Lifetimes

Protein Diffusion and Macromolecular Crowding in Thylakoid Membranes

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