Protonation-induced changes in the macroorganization of LHCII monolayers

Andreeva, Tonya; Krumova, Sashka; Minkov, I.; Busheva, Mira; Lalchev, Zdravko; Taneva, Stefka G.

doi:10.1016/j.colsurfa.2013.12.044

Cited by 5 publications

(16 citation statements)

References 64 publications

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“…It is believed that low-pH induces protonation of PsbS that triggers conformational changes in LHCII via direct contact with PsbS monomers (52,53). Isolated LHCII complexes have also been shown to alter their structural features in response to pH changes-in vitro the protonation of LHCII trimers leads to the formation of aggregates (54) and when assembled in monolayers (at the buffer/air interface) the protonated LHCII exhibits a higher order of organization and a significantly higher stability as compared with the partly deprotonated LHCII (55). The protonation of PsbS and LHCII drives LHCII aggregation, LHCII migration from PSII-bound to PSI-bound state (state transitions) and/or energy spillover from PSII toward PSI (as suggested by (44)), and de-epoxidation of LHCII-bound xanthophylls (xanthophyll cycle), all of them factors that ensure the completion of extensive NPQ.…”

Section: Discussionmentioning

confidence: 96%

Low pH Modulates the Macroorganization and Thermal Stability of PSII Supercomplexes in Grana Membranes

Stoichev

Krumova

Andreeva

et al. 2015

Biophysical Journal

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Protonation of the lumen-exposed residues of some photosynthetic complexes in the grana membranes occurs under conditions of high light intensity and triggers a major photoprotection mechanism known as energy dependent nonphotochemical quenching. We have studied the role of protonation in the structural reorganization and thermal stability of isolated grana membranes. The macroorganization of granal membrane fragments in protonated and partly deprotonated state has been mapped by means of atomic force microscopy. The protonation of the photosynthetic complexes has been found to induce large-scale structural remodeling of grana membranes-formation of extensive domains of the major light-harvesting complex of photosystem II and clustering of trimmed photosystem II supercomplexes, thinning of the membrane, and reduction of its size. These events are accompanied by pronounced thermal destabilization of the photosynthetic complexes, as evidenced by circular dichroism spectroscopy and differential scanning calorimetry. Our data reveal a detailed nanoscopic picture of the initial steps of nonphotochemical quenching.

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Section: Discussionmentioning

confidence: 96%

Low pH Modulates the Macroorganization and Thermal Stability of PSII Supercomplexes in Grana Membranes

Stoichev

Krumova

Andreeva

et al. 2015

Biophysical Journal

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“…A monomolecular layer approach, combined with several molecular spectroscopy and imaging techniques, was applied to get insight into the molecular and photophysical mechanisms underlying such a regulatory activity. The monomolecular layer system has been shown to provide a suitable model for study of the molecular organization and structural features of LHCII, in which the complex retains its native structure and functional properties, manifested by efficient excitation energy transfer. − …”

Section: Introductionmentioning

confidence: 99%

A Key Role of Xanthophylls That Are Not Embedded in Proteins in Regulation of the Photosynthetic Antenna Function in Plants, Revealed by Monomolecular Layer Studies

et al. 2016

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The main physiological function of LHCII (light-harvesting pigment-protein complex of photosystem II), the largest photosynthetic antenna complex of plants, is absorption of light quanta and transfer of excitation energy toward the reaction centers, to drive photosynthesis. However, under strong illumination, the photosynthetic apparatus faces the danger of photodegradation and therefore excitations in LHCII have to be down-regulated, e.g., via thermal energy dissipation. One of the elements of the regulatory system, operating in the photosynthetic apparatus under light stress conditions, is a conversion of violaxanthin, the xanthophyll present under low light, to zeaxanthin, accumulated under strong light. In the present study, an effect of violaxanthin and zeaxanthin on the molecular organization and the photophysical properties of LHCII was studied in a monomolecular layer system with application of molecular imaging (atomic force microscopy, fluorescence lifetime imaging microscopy) and spectroscopy (UV-Vis absorption, FTIR, fluorescence spectroscopy) techniques. The results of the experiments show that violaxanthin promotes the formation of supramolecular LHCII structures preventing dissipative excitation quenching while zeaxanthin is involved in the formation of excitonic energy states able to quench chlorophyll excitations in both the higher (B states) and lower (Q states) energy levels. The results point to a strategic role of xanthophylls that are not embedded in a protein environment, in regulation of the photosynthetic light harvesting activity in plants.

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“…The π/ A isotherms of both protonated and partly deprotonated LHCII monolayers (Figure a) show two (low- and high-surface pressure) regions with different slopes, suggesting that conformational and/or orientational changes take place as a result of the monolayer compression (for detailed discussion, see ref ). We have previously established the optimal conditions for the formation of stable monolayers and have found that the protonated and partly deprotonated LHCII exhibit distinct supramolecular organizationthe LHCII and p-LHCII monolayers are composed of trimers assembled in either loosely packed homogeneous well-ordered monolayer areas or tightly packed heterogeneous disordered phase, with these two being in different proportions in the two types of monolayers . To characterize the LHCII conformation in monolayers at surface pressures below and above the transition surface pressure in the isotherms, i.e., at 10 and 30 mN/m, respectively, we apply PM-IRRAS; typical spectra are presented in Figure b,c.…”

Section: Results and Discussionmentioning

confidence: 99%

“…The protonation-induced switch in the LHCII configuration yielded more tightly packed, stable but flexible macroorganization (in terms of reversibility of the compression-induced structural rearrangements) of the complexes. Brewster angle microscopy images of LHCII and p-LHCII monolayers unambiguously demonstrated that the protonation exerted strong effect on the proteins supramolecular organization and led to significant remodeling of the monolayer, making it more heterogeneous as compared to the one characteristic for the partly deprotonated state …”

Section: Introductionmentioning

confidence: 96%

“…LHCII monolayers on liquid and solid supports are extensively investigated as a suitable model system for the study of the supramolecular organization of the complex under different experimental conditions that are not feasible to perform in the highly complex and crowded (80% protein) thylakoid membrane. − We have recently examined the relations between the lateral LHCII rearrangements and the conformational changes during the molecular switch from light-harvesting to photoprotective state of LHCII by comparing the physicochemical properties of partly deprotonated (LHCII, light-harvesting state) and protonated (p-LHCII, photoprotective state) LHCII in Langmuir monolayers . We have found a different contour of the π/ A isotherms and difference in the hysteresis of the LHCII and p-LHCII monolayers.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Protonation on the Secondary Structure and Orientation of Plant Light-Harvesting Complex II Studied by PM-IRRAS

et al. 2015

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The major light-harvesting pigment-protein complex of photosystem II, LHCII, has a crucial role in the distribution of the light energy between the two photosystems, the efficient light capturing and protection of the reaction centers and antennae from overexcitation. In this work direct structural information on the effect of LHCII protonation, which mimics the switch from light-harvesting to photoprotective state of the protein, was revealed by polarization-modulated infrared reflection-absorption spectroscopy (PM-IRRAS). PM-IRRAS on LHCII monolayers verified that the native helical structure of the protein is preserved in both partly deprotonated (pH 7.8, LHCII) and protonated (pH 5.2, p-LHCII) states. At low surface pressure, 10 mN/m, the orientation of the α-helices in these two LHCII states is different-tilted (θ ≈ 40°) in LHCII and nearly vertical (θ ≈ 90°) in p-LHCII monolayers; the partly deprotonated complex is more hydrophilic than the protonated one and exhibits stronger intertrimer interactions. At higher surface pressure, 30 mN/m, which is typical for biological membranes, the protonation affects neither the secondary structure nor the orientation of the transmembrane α-helices (tilted ∼45° relative to the membrane surface in both LHCII states) but weakens the intermolecular interactions within and/or between the trimers.

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Protonation-induced changes in the macroorganization of LHCII monolayers

Cited by 5 publications

References 64 publications

Low pH Modulates the Macroorganization and Thermal Stability of PSII Supercomplexes in Grana Membranes

Low pH Modulates the Macroorganization and Thermal Stability of PSII Supercomplexes in Grana Membranes

A Key Role of Xanthophylls That Are Not Embedded in Proteins in Regulation of the Photosynthetic Antenna Function in Plants, Revealed by Monomolecular Layer Studies

Effect of Protonation on the Secondary Structure and Orientation of Plant Light-Harvesting Complex II Studied by PM-IRRAS

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