Light-induced Formation of Dimeric LHCII
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Light-induced Formation of Dimeric LHCII
It emerges from numerous experiments that LHCII, the major photosynthetic antenna complex of plants, can appear not only in the trimeric or monomeric states but also as a dimer. We address the problem whether the dimeric form of the complex is just a simple intermediate element of the trimer-monomer transformation or if it can also be a physiologically relevant molecular organization form? Dimers of LHCII were analyzed with application of native electrophoresis, time-resolved fluorescence spectroscopy, and fluorescence correlation spectroscopy. The results reveal the appearance of two types of LHCII dimers: one formed by the dissociation of one monomer from the trimeric structure and the other formed by association of monomers into a distinctively different molecular organizational form, characterized by a high rate of chlorophyll excitation quenching. The hypothetical structure of such an energy quencher is proposed. The high light-induced LHCII dimerization is discussed as a potential element of the photoprotective response in plants.
Dimer; Fluorescence quenching; LHCII complex; Photoprotection; Spinacia oleracea.
Electrophoretic analysis of LHCII oligomeric forms in LHCII preparations isolated from
Spinacia oleracea leaves. Spinach leaves were dark-adapted (LHCII) or pre-illuminated with light intensity of 1200 µmol photons m −2 s −1 (LHCII-HL) before LHCII isolation. LHCII was suspended in 0.1% DM. Figure shows exemplary results of the electrophoretic gel analyses with band assignment ( FP free pigments fraction)
Electrophoretic analysis of LHCII oligomeric forms in LHCII samples illuminated with different light intensities. LHCII was suspended in 0.1% DM. Electrophoresis was conducted under constant illumination starting from the sample loading. Each slot was illuminated with different light intensity (from 11 µmol photons m
−2 s −1 to 1240 µmol photons m −2 s −1). This was carried out by gel illumination in an intensity gradient of a LED light source (as it is schematically presented in Fig. S1). Light intensity in each slot was precisely measured using a photometer before commencing each experiment. Upper panel shows exemplary results of the electrophoretic gel analyses with band assignment ( FP free pigments fraction). Lower panel presents the quantity analysis of LHCII trimers, dimers, and monomers in the samples. Relative intensities of the bands corresponding to different LHCII forms were quantified by scans analyzed with ImageJ2x software. Experiment was repeated ten times. Similar, exemplary effect of different light intensities on the LHCII trimers and monomers mixture is presented as Supplementary data (Fig. S2)
Normalized autocorrelation curves of different LHCII forms. Monomers (
a) and trimers ( b) were suspended in 0.05 and 0.03% DM solution, respectively. Dark-adapted LHCII trimers and monomers mixture in 0.1% DM solution ( c) were subjected to illumination with blue light intensity of 100 µmol photons m −2 s −1 for 30 min ( d). Diffusion coefficient values [as mean values ± SD ( n = 8 biological replicates)] of the LHCII forms detected during FCS measurements are presented in the figure
Amplitude-weighted average lifetime <
τ> values in relation to amplitude of lifetime components measured from LHCII trimer, dimer, and monomer. Values of average lifetime were calculated on the basis of the fluorescence decay kinetics fitted with three components characterized by the following lifetimes: τ
1 = 3.7 ns, τ
2 = 1.8 ns and τ
3 = 0.3 ns. Average lifetimes for the LHCII trimers and monomers are presented as mean values. Error bars indicate standard deviation ( n = 10 biological replicates). Fluorescence intensity decays were analyzed by deconvolution with the instrument response function and analyzed as a sum of exponential terms. The quality of the fit was judged from the χ 2 value (~1). Excitation and detection was at 470 and 680 nm, respectively. Fluorescence decay curves were recorded from LHCII complexes located in polyacrylamide gel separated by means of the non-denaturing gel electrophoresis
77 K Chl
a fluorescence emission spectra of the LHCII dimers. Dimers were induced by low (18 µmol photons m −2 s −1) or high (1200 µmol photons m −2 s −1) light intensity. The spectra were normalized in the maximum. Spectra were measured from the LHCII complexes located in polyacrylamide gel
Room temperature CD spectra in the red region of different LHCII forms. The spectra were measured from the LHCII complexes separated by means of the non-denaturing gel electrophoresis. During separation the LHCII trimers and monomers mixture was illuminated with high light intensity (HL, 1200 µmol photons m
−2 s −1). The spectra were registered from the complexes located in polyacrylamide gel. Spectra are normalized in the negative maximum at 650 nm
Proposed graphical presentation of high light-induced dimer structure created using YASARA (Krieger et al. 2002).
a Top view (from the stromal side), b bottom view (from the lumenal side), c, d side views from the membrane plane perspectives. For clarity of presentation, interacting Chl a and b are marked red. Distance between Mg 2+ ions in marked chlorophylls is equal to 0.906 nm. The illustration is based on the crystal structure of LHCII from PDB (ID: 2BHW). blue Chl a, green Chl b, yellow violaxanthin, magenta neoxanthin, orange lutein
All figures (7)
Blue-light-controlled Photoprotection in Plants at the Level of the Photosynthetic Antenna Complex LHCII
WI Gruszecki et al.
J Plant Physiol 167 (1), 69-73.
Plants have developed several adaptive regulatory mechanisms, operating at all the organization levels, to optimize utilization of light energy and to protect themselves …
Light-harvesting Complex II (LHCII) and Its Supramolecular Organization in Chlamydomonas Reinhardtii
B Drop et al.
Biochim Biophys Acta 1837 (1), 63-72.
LHCII is the most abundant membrane protein on earth. It participates in the first steps of photosynthesis by harvesting sunlight and transferring excitation energy to th …
Low-light-induced Formation of Semicrystalline Photosystem II Arrays in Higher Plant Chloroplasts
H Kirchhoff et al.
Biochemistry 46 (39), 11169-76.
Remodeling of photosynthetic machinery induced by growing spinach plants under low light intensities reveals an up-regulation of light-harvesting complexes and down-regul …
Light Harvesting Control in Plants
FEBS Lett 592 (18), 3030-3039.
In 1991, my colleagues and I published a hypothesis article that proposed a mechanism that controls light harvesting in plants and protects them against photodamage. The …
Quality Control of PSII: Behavior of PSII in the Highly Crowded Grana Thylakoids Under Excessive Light
Y Yamamoto et al.
Plant Cell Physiol 55 (7), 1206-15.
The grana thylakoids of higher plant chloroplasts are crowded with PSII and the associated light-harvesting complexes (LHCIIs). They constitute supercomplexes, and often …
PubMed Central articles
Four Distinct Trimeric Forms of Light-Harvesting Complex II Isolated From the Green Alga Chlamydomonas Reinhardtii
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Photosynth Res 142 (2), 195-201.
Light-harvesting complex II (LHCII) absorbs light energy and transfers it primarily to photosystem II in green algae and land plants. Although the trimeric structure of L …
Characterization of Protein Radicals in Arabidopsis
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Front Physiol 10, 958.
Oxidative modification of proteins in photosystem II (PSII) exposed to high light has been studied for a few decades, but the characterization of protein radicals formed …
ONE-HELIX PROTEIN2 (OHP2) Is Required for the Stability of OHP1 and Assembly Factor HCF244 and Is Functionally Linked to PSII Biogenesis
D Hey et al.
Plant Physiol 177 (4), 1453-1472.
The members of the light-harvesting complex protein family, which include the one-helix proteins (OHPs), are characterized by one to four membrane-spanning helices. These …
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Light-Harvesting Protein Complexes / chemistry
Light-Harvesting Protein Complexes / metabolism
Photosynthesis / radiation effects
Photosystem II Protein Complex / chemistry
Photosystem II Protein Complex / metabolism
Protein Structure, Secondary
Spinacia oleracea / metabolism
Spinacia oleracea / radiation effects
Thylakoids / metabolism
Light-Harvesting Protein Complexes
Photosystem II Protein Complex