Articles de revues : « Lhc protein »

1

Darr, S. C., S. C. Somerville et C. J. Arntzen. « Monoclonal antibodies to the light-harvesting chlorophyll a/b protein complex of photosystem II. » Journal of Cell Biology 103, n^o 3 (1 septembre 1986) : 733–40. http://dx.doi.org/10.1083/jcb.103.3.733.

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A collection of 17 monoclonal antibodies elicited against the light-harvesting chlorophyll a/b protein complex which serves photosystem II (LHC-II) of Pisum sativum shows six classes of binding specificity. Antibodies of two of the classes recognize a single polypeptide (the 28- or the 26- kD polypeptides), thereby suggesting that the two proteins are not derived from a common precursor. Other classes of antibodies cross-react with several polypeptides of LHC-II or with polypeptides of both LHC-II and the light-harvesting chlorophyll a/b polypeptides of photosystem I (LHC-I), indicating that there are structural similarities among the polypeptides of LHC-II and LHC-I. The evidence for protein processing by which the 26-, 25.5-, and 24.5-kD polypeptides are derived from a common precursor polypeptide is discussed. Binding studies using antibodies specific for individual LHC-II polypeptides were used to quantify the number of antigenic polypeptides in the thylakoid membrane. 27 copies of the 26-kD polypeptide and two copies of the 28-kD polypeptide were found per 400 chlorophylls. In the chlorina f2 mutant of barley, and in intermittent light-treated barley seedlings, the amount of the 26-kD polypeptide in the thylakoid membranes was greatly reduced, while the amount of 28-kD polypeptide was apparently not affected. We propose that stable insertion and assembly of the 28-kD polypeptide, unlike the 26-kD polypeptide, is not regulated by the presence of chlorophyll b.

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Rochaix, Jean-David, et Roberto Bassi. « LHC-like proteins involved in stress responses and biogenesis/repair of the photosynthetic apparatus ». Biochemical Journal 476, n^o 3 (14 février 2019) : 581–93. http://dx.doi.org/10.1042/bcj20180718.

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AbstractLHC (light-harvesting complex) proteins of plants and algae are known to be involved both in collecting light energy for driving the primary photochemical reactions of photosynthesis and in photoprotection when the absorbed light energy exceeds the capacity of the photosynthetic apparatus. These proteins usually contain three transmembrane (TM) helices which span the thylakoid membranes and bind several chlorophyll, carotenoid and lipid molecules. In addition, the LHC protein family includes LHC-like proteins containing one, two, three or even four TM domains. One-helix proteins are not only present in eukaryotic photosynthetic organisms but also in cyanobacteria where they have been named high light-inducible proteins. These small proteins are probably the ancestors of the members of the extant LHC protein family which arouse through gene duplications, deletions and fusions. During evolution, some of these proteins have diverged and acquired novel functions. In most cases, LHC-like proteins are induced in response to various stress conditions including high light, high salinity, elevated temperature and nutrient limitation. Many of these proteins play key roles in photoprotection, notably in non-photochemical quenching of absorbed light energy. Moreover, some of these proteins appear to be involved in the regulation of chlorophyll synthesis and in the assembly and repair of Photosystem II and also of Photosystem I possibly by mediating the insertion of newly synthesized pigments into the photosynthetic reaction centers.

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Jackowski, Grzegorz, et Ewa Kluck. « The Oligomeric Arrangement of the Light-Harvesting Chlorophyll a/6-Protein Complex of Photosystem II ». Zeitschrift für Naturforschung C 49, n^o 5-6 (1 juin 1994) : 337–42. http://dx.doi.org/10.1515/znc-1994-5-610.

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Abstract The light-harvesting chlorophyll a/b-protein complex of photosystem II (LHC II) was isolated from carnation (Dianthus caryophyllus L.) leaves by K+-induced aggregation of n-hep-tylthioglucoside-treated photosystem II particles. When solubilized with a mixture of lithium docedyl sulphate, octyl-β-D-glucopyranoside and dodecyl-β-D-maltoside the LHC II was re solved by mild sodium dodecyl sulphate-polyacrylamide gel electrophoresis into four oligomeric forms and a monomeric one. LHC II contained five major polypeptides only two of which (27 and 26 kDa) were found to be its authentic components. The oligomeric forms of LHC II were found to differ in the stoichiometric ratios of the polypeptides present. The 26 kD a polypeptide was enriched in the largest oligomeric forms while the 27 kDa polypeptide tended to form a monomer or to assemble as lower oligomeric states of LHC II.

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Nield, Jon, Christiane Funk et James Barber. « Supermolecular structure of photosystem II and location of the PsbS protein ». Philosophical Transactions of the Royal Society of London. Series B : Biological Sciences 355, n^o 1402 (29 octobre 2000) : 1337–44. http://dx.doi.org/10.1098/rstb.2000.0695.

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This paper addresses the question of whether the PsbS protein of photosystem two (PS II) is located within the LHC II–PS II supercomplex for which a three–dimensional structure has been obtained by cryoelectron microscopy and single particle analysis. The PsbS protein has recently been implicated as the site for non–photochemical quenching. Based both on immunoblotting analyses and structural considerations of an improved model of the spinach LHC II–PS II supercomplex, we conclude that the PsbS protein is not located within the supercomplex. Analyses of other fractions resulting from the solubilization of PS II–enriched membranes derived from spinach suggest that the PsbS protein is located in the LHC II–rich regions that interconnect the supercomplex within the membrane.

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Sprague, S. G., E. L. Camm, B. R. Green et L. A. Staehelin. « Reconstitution of light-harvesting complexes and photosystem II cores into galactolipid and phospholipid liposomes. » Journal of Cell Biology 100, n^o 2 (1 février 1985) : 552–57. http://dx.doi.org/10.1083/jcb.100.2.552.

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Chlorophyll a/b light-harvesting complexes (chl a/b LHC) and photosystem II (PSII) cores were isolated from an octyl glucoside-containing sucrose gradient after solubilization of barley thylakoid membranes with Triton X-100 and octyl glucoside. No cation precipitation step was necessary to collect the chl a/b LHC. PAGE under mildly denaturing and fully denaturing conditions showed that the chl a/b LHC fraction contained chlorophyll-protein complexes CP27, CP29, and CP64. The PSII core material contained CP43 and CP47, and little contamination by other nonpigmented polypeptides. Freeze-fracture electron microscopy of the chl a/b LHC after reconstitution into digalactosyldiglyceride (DG) or phosphatidylcholine (PC) vesicles showed that the protein particles (approximately 7.5 +/- 1.6 nm) were approximately 99 and 90% randomly dispersed, respectively, in the liposomes. Addition of Mg++ produced particle aggregation and membrane adhesion in chl a/b LHC-DG liposomes in a manner analogous to that described for LHC-PC liposomes. Reconstitution of PSII cores into DG vesicles also produced proteoliposomes with randomly dispersed particles (approximately 7.5 +/- 1.6 nm). In contrast, PSII-PC mixtures formed convoluted networks of tubular membranes that exhibited very few fracture faces. Most of the protein particles (approximately 7.0 +/- 1.5 nm) were seen trapped between, rather than embedded in, the membranes. The interaction between the zwitterionic head group of the phosphatidyl choline and the negatively charged PSII core may be responsible for the unusual membrane structures observed.

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Takeuchi, TS, et JP Thornber. « Heat-Induced Alterations in Thylakoid Membrane Protein Composition in Barley ». Functional Plant Biology 21, n^o 6 (1994) : 759. http://dx.doi.org/10.1071/pp9940759.

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Biochemical and spectroscopic studies on the effects of high temperatures (45-47� C) over a 1 h period on the protein composition, fluorescence and photochemical activities of the barley thylakoid membrane were made. Photosystem II (PS II) activity decreased as expected, and photosystem I (PS I) activity also unexpectedly decreased. Our data support previous conclusions that the decrease in PS I activity is largely due to inactivation (or loss) of a component between the two photosystems. A two-dimensional electrophoretic system permitted first the separation of the thylakoid pigment-protein complexes of unstressed and stressed plants, followed by a determination of their subunit composition. The changes in the protein composition of each pigment-protein complex in response to elevated temperatures were monitored. Heat changed the quaternary structure of PS II and resulted in removal of the oxygen-evolving enhancer proteins from the thylakoid, but did essentially no damage to the PS I complex. The PS II core complex dissociated from a dimeric form to a monomeric one, and the major LHC II component (LHC IIb) changed from a trimeric to a monomeric form. The pigments that are lost from thylakoids during heat stress are mainly removed from the PS II pigment-proteins.

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Schuster, G., M. Dewit, L. A. Staehelin et I. Ohad. « Transient inactivation of the thylakoid photosystem II light-harvesting protein kinase system and concomitant changes in intramembrane particle size during photoinhibition of Chlamydomonas reinhardtii. » Journal of Cell Biology 103, n^o 1 (1 juillet 1986) : 71–80. http://dx.doi.org/10.1083/jcb.103.1.71.

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Light-dependent reduction of the plastoquinone pool regulates the activity of the thylakoid-bound protein kinase which phosphorylates the light harvesting chlorophyll a,b-protein complex (LHC II) and regulates energy distribution between photosystems II (PS II) and I (Staehelin, L. A., and C. J. Arntzen, 1983, J. Cell Biol., 97:1327-1337). Since reduction of plastoquinone by PS II is abolished in photoinhibited thylakoids due to loss of the secondary electron acceptor QB protein (Kyle, D. J., I. Ohad, and C. J. Arntzen, 1984, Proc. Natl. Acad. Sci. USA, 81:4070-4074), it was of interest to examine the activity of the LHC II protein kinase system during photoinhibition and recovery of PS II activity. The kinase activity was assessed both in vivo and in vitro in Chlamydomonas cells exposed to high light intensity (photoinhibition) and recovery at low light intensity. The kinase activity was progressively reduced during photoinhibition and became undetectable after 90 min. The inactive LHC II-kinase system could not be reactivated in vitro either by light or by reduction of the plastoquinone pool following addition of reduced duroquinone (TMQH2). The LHC II polypeptides were dephosphorylated in vivo when cells, prelabeled with [32P]orthophosphate before exposure to high light intensity, were transferred to photoinhibiting light in the presence of [32P]orthophosphate. In vivo recovery of the LHC II-kinase activity, elicited by the addition of TMQH2 to the assay system, did not require restoration of QB-dependent electron flow or de novo protein synthesis, either in the cytoplasm or in the chloroplast. Mild sonication of thylakoids isolated from photoinhibited cells restored the ability of the LHC II protein kinase system to be activated in vitro by addition to TMQH2. Restoration of the light-activated LHC-II kinase required recovery of QB-dependent electron flow. At the structural level, photoinhibition did not affect the ratio of grana/stroma thylakoids. A reduction of approximately 20% of the 11-17-nm intramembrane particles and an equivalent increase in the number of 6-10.5-nm particles was observed on the E-fracture faces of stacked thylakoid membranes. Similar but smaller changes were observed also on the E-fracture faces of unstacked thylakoid membranes (more 10-14-nm and less 6-9-nm particles) and P-fracture faces of stacked thylakoid membranes (more 6-8- and less 9.5-13-nm particles). All these structural changes were reversed to normal values during recovery of PS II activity.(ABSTRACT TRUNCATED AT 400 WORDS)

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8

Evans, JR. « Acclimation by the Thylakoid Membranes to Growth Irradiance and the Partitioning of Nitrogen Between Soluble and Thylakoid Proteins ». Functional Plant Biology 15, n^o 2 (1988) : 93. http://dx.doi.org/10.1071/pp9880093.

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Three characteristics of shade plants are reviewed. Firstly, they have relatively more chlorophyll b and the associated light-harvesting chlorophyll a/b-protein complex (LHC). Two currently accepted reasons for this are not supported by quantitative analysis. Instead, the reduced protein cost of complexing chlorophyll in LHC and the turnover of the 32 kDa herbicide binding protein are considered. Secondly, shade plants have low electron transport capacities per unit of chlorophyll. This is primarily related to a reduction in the amount of electron transport components such as the cytochrome f complex and the ATPase. The nitrogen cost of the thylakoid membranes per unit of light absorbed is thereby reduced, but the irradiance range over which light is used with high efficiency is also reduced. Thirdly, shade plants have less RuP2 carboxylase and other soluble proteins for a given amount of chlorophyll. However, while the ratio of RuP2 carboxylase protein to thylakoid protein declined, the ratio of the RuP2 carboxylase activity to electron transport activity increased. For several species, the relationship between the rate of CO2 assimilation and leaf nitrogen content depends on the irradiance during growth.

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Ganeteg, Ulrika, Frank Klimmek et Stefan Jansson. « Lhca5 – an LHC-Type Protein Associated with Photosystem I ». Plant Molecular Biology 54, n^o 5 (mars 2004) : 641–51. http://dx.doi.org/10.1023/b:plan.0000040813.05224.94.

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10

Lyon, M. K., et K. R. Miller. « Crystallization of the light-harvesting chlorophyll a/b complex within thylakoid membranes. » Journal of Cell Biology 100, n^o 4 (1 avril 1985) : 1139–47. http://dx.doi.org/10.1083/jcb.100.4.1139.

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We have found that treatment of the photosynthetic membranes of green plants, or thylakoids, with the nonionic detergent Triton X-114 at a 10:1 ratio has three effects: (a) photosystem I and coupling factor are solubilized, so that the membranes retain only photosystem II (PS II) and its associated light-harvesting apparatus (LHC-II); (b) LHC-II is crystallized, and so is removed from its normal association with PS II; and (c) LHC-II crystallization causes a characteristic red shift in the 77 degrees K fluorescence from LHC-II. Treatment of thylakoids with the same detergent at a 20:1 ratio results in an equivalent loss of photosystem I and coupling factor, with LHC-II and PS II being retained by the membranes. However, no LHC-II crystals are formed, nor is there a shift in fluorescence. Thus, isolation of a membrane protein is not required for its crystallization, but the conditions of detergent treatment are critical. Membranes with crystallized LHC-II retain tetrameric particles on their surface but have no recognizable stromal fracture face. We have proposed a model to explain these results: LHC-II is normally found within the stromal half of the membrane bilayer and is reoriented during the crystallization process. This reorientation causes the specific fluorescence changes associated with crystallization. Tetrameric particles, which are not changed in any way by the crystallization process, do not consist of LHC-II complexes. PS II appears to be the only other major complex retained by these membranes, which suggests that the tetramers consist of PS II.

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Cleland, RE, B. Demmig-Adams, WW Iii Adams et K. Winter. « Phosphorylation State of the Light-Harvesting Chlorophyll-Protein Complex of Photosystem II and Chlorophyll Fluorescence Characteristics in Monstera deliciosa Liebm. And Glycine max (L.) Merrill in Response to Light ». Functional Plant Biology 17, n^o 5 (1990) : 589. http://dx.doi.org/10.1071/pp9900589.

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Upon a transition from darkness to (low) light, leaves of the rainforest plant Monstera deliciosa which had developed in deep shade exhibited a decline in PS II chlorophyll fluorescence (FO and FM) and a net increase in PS I fluorescence (FO and FM) indicative of a state transition. Upon this transition, LHC-II became phosphorylated. Phosphorylation of LHC-II was maintained upon exposure of M. deliciosa leaves to photon flux densities (PFDs) representing an excess of light, independent of whether the excess of light was created by exposing the leaves to high PFDs in air (where photosynthesis and photorespiration can proceed) or by exposing them to intermediate PFDs in 2% O2 without CO2 (where photosynthesis and photorespiration are prevented). This was in contrast to the response of soybean leaves, in which LHC-II became dephosphorylated under both of these conditions representing an excess of light. These different response patterns may be associated with a heterogeneity of LHC-II populations and/or differences in the expression of energy dissipation in the chlorophyll pigment bed between the two types of leaves.

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12

Williams, Richard S., John F. Allen, Anthony P. R. Brain et R. John Ellis. « Effect of Mg2+ on excitation energy transfer between LHC II and LHC I in a chlorophyll-protein complex ». FEBS Letters 225, n^o 1-2 (10 décembre 1987) : 59–66. http://dx.doi.org/10.1016/0014-5793(87)81131-6.

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13

Farchaus, J., R. A. Dilley et W. A. Cramer. « Selective inhibition of the spinach thylakoid LHC II protein kinase ». Biochimica et Biophysica Acta (BBA) - Bioenergetics 809, n^o 1 (août 1985) : 17–26. http://dx.doi.org/10.1016/0005-2728(85)90162-8.

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ROKKA, Anne, Marjaana SUORSA, Ammar SALEEM, Natalia BATTCHIKOVA et Eva-Mari ARO. « Synthesis and assembly of thylakoid protein complexes : multiple assembly steps of photosystem II ». Biochemical Journal 388, n^o 1 (10 mai 2005) : 159–68. http://dx.doi.org/10.1042/bj20042098.

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To study the synthesis and assembly of multisubunit thylakoid protein complexes, we performed [35S]Met pulse and chase experiments with isolated chloroplasts and intact leaves of spinach (Spinacia oleracea L.), followed by Blue Native gel separation of the (sub)complexes and subsequent identification of the newly synthesized and assembled protein subunits. PSII (photosystem II) core subunits were the most intensively synthesized proteins, particularly in vitro and at high light intensities in vivo, and could be sequestered in several distinct PSII subassemblies. Newly synthesized D1 was first found in the reaction centre complex that also contained labelled D2 and two labelled low-molecular-mass proteins. The next biggest PSII subassembly contained CP47 also. Then PsbH was assembled together with at least two other labelled chloroplast-encoded low-molecular-mass subunits, PsbM and PsbTc, and a nuclear-encoded PsbR. Subsequently, CP43 was inserted into the PSII complex concomitantly with PsbK. These assembly steps seemed to be essential for the dimerization of PSII core monomers. Intact PSII core monomer was the smallest subcomplex harbouring the newly synthesized 33 kDa oxygen-evolving complex protein PsbO. Nuclear-encoded PsbW was synthesized only at low light intensities concomitantly with Lhcb polypeptides and was distinctively present in PSII–LHCII (where LHC stands for light-harvesting complex) supercomplexes. The PsbH protein, on the contrary, was vigorously synthesized and incorporated into PSII core monomers together with the D1 protein, suggesting an intrinsic role for PsbH in the photoinhibition-repair cycle of PSII.

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Mäenpää, Pirkko, et Bertil Andersson. « Photosystem II Heterogeneity and Long-Term Acclimation of Light-Harvesting ». Zeitschrift für Naturforschung C 44, n^o 5-6 (1 juin 1989) : 403–6. http://dx.doi.org/10.1515/znc-1989-5-611.

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Abstract The main chlorophyll a/b protein complex of the chloroplast thylakoid membrane is organized into two subpopulations; one inner which is tightly bound to the photosystem II core and one outer which is bound more loosely or peripherally. In this study, changes in the LHC II com position due to long-term light acclimation were analyzed and quantified in spinach thylakoids and isolated stroma lamellae vesicles. The results show that; photosystem II located in the appressed thylakoid regions (α-centres) which have a relatively large antenna size, contains both the inner and outer LHC II with a predominance of the latter (58-70%). At low light the antenna size o f the α-center becomes larger due to a specific increase of the outer pool o f LHC II. The antenna size of photosystem II in the stroma thylakoids (β-centres) is smaller and contains mainly or only the inner LHC II pool. In contrast to the α-centres the β-centres centres do not undergo adaptive changes in their size in response to long-term changes in the light intensities.

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Morishige, Daryl T., et J. Philip Thornber. « Identification of a novel light-harvesting complex II protein (LHC IIc?) ». Photosynthesis Research 39, n^o 1 (janvier 1994) : 33–38. http://dx.doi.org/10.1007/bf00027140.

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Zhao, Yongguo, Hua Kong, Yunling Guo et Zhi Zou. « Light-harvesting chlorophyll a/b-binding protein-coding genes in jatropha and the comparison with castor, cassava and arabidopsis ». PeerJ 8 (28 janvier 2020) : e8465. http://dx.doi.org/10.7717/peerj.8465.

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The Lhc (light-harvesting chlorophyll a/b-binding protein) superfamily represents a class of antennae proteins that play indispensable roles in capture of solar energy as well as photoprotection under stress conditions. Despite their importance, little information has been available beyond model plants. In this study, we presents a first genome-wide analysis of Lhc superfamily genes in jatropha (Jatropha curcas L., Euphorbiaceae), an oil-bearing plant for biodiesel purpose. A total of 27 members were identified from the jatropha genome, which were shown to distribute over nine out of the 11 chromosomes. The superfamily number is comparable to 28 present in castor (Ricinus communis, Euphorbiaceae), but relatively less than 35 in cassava (Manihot esculenta, Euphorbiaceae) and 34 in arabidopsis (Arabidopsis thaliana) that experienced one or two recent whole-genome duplications (WGDs), respectively. In contrast to a high number of paralogs present in cassava and arabidopsis, few duplicates were found in jatropha as observed in castor, corresponding to no recent WGD occurred in these two species. Nevertheless, 26 orthologous groups representing four defined families were found in jatropha, and nearly one-to-one orthologous relationship was observed between jatropha and castor. By contrast, a novel group named SEP6 was shown to have been lost in arabidopsis. Global transcriptome profiling revealed a predominant expression pattern of most JcLhc superfamily genes in green tissues, reflecting their key roles in photosynthesis. Moreover, their expression profiles upon hormones, drought, and salt stresses were also investigated. These findings not only improve our knowledge on species-specific evolution of the Lhc supergene family, but also provide valuable information for further studies in jatropha.

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Muraja-Ljubičić, Jasmina, Mercedes Wrischer et Nikola Ljubešić. « Influence of the Herbicides Amitrole and Norflurazon on Greening of Illuminated Potato Microtubers ». Zeitschrift für Naturforschung C 54, n^o 5-6 (1 juin 1999) : 333–36. http://dx.doi.org/10.1515/znc-1999-5-607.

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Abstract Potato microtubers turn green within a few days when kept in the light. The initial phases in this process were observed as early as 12 hours after the onset of illumination. The changes included a pronounced increase in chlorophyll and carotenoid concentrations, accompanied by changes in the protein pattern and in the transformation of amyloplasts and leucoplasts to chloroplasts. The bleaching herbicides amitrole and norflurazon inhibited the synthesis of carotenoids in the illuminated potato microtubers. However, amitrole only delayed greening and an increase in chlorophyll and carotenoid levels became visible as late as four days after the onset of illumination, and the LHC II protein of the photosynthetic membrane was not detected before the seventh day of light exposure. Norflurazon, in contrast, acted as a stronger inhibitor, and microtuber tissues stayed yellowish throughout the experiment. The concentrations of both carotenoids and chlorophylls were very low in tissues treated with this herbicide. The LHC II protein could not be detected after a seven-day light exposure and the plastids were damaged, small in size, without normal thylakoids and with numerous plastoglobules.

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Li, Xiu, Rui Yang, Liulong Li, Ke Liu, Matthew Tom Harrison, Shah Fahad, Mingmei Wei, Lijun Yin, Meixue Zhou et Xiaoyan Wang. « Physiological and Molecular Responses of Wheat to Low Light Intensity ». Agronomy 13, n^o 1 (16 janvier 2023) : 272. http://dx.doi.org/10.3390/agronomy13010272.

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Here we document physiological and molecular attributes of three wheat cultivars (ZM9023, YM158 and FM1228) under low light intensity with advanced technologies, including non-standard quantitative technology and quantitative proteomics technology. We found lower dry matter accumulation of YM158 compared with ZM 9023 and FM1228 under low light intensities due to up-regulation of photosynthetic parameters electron transport rate (ETR), Y(II), Fv/Fm, Chl (a + b) of YM158 and down-regulation of Chl a/b. ETR, Y(II) and Fv/Fm significantly decreased between ZM9023 and FM1228. The ETR between PSII and PSI of YM158 increased, while light use efficiency (LUE) of ZM9023 and FM1228 decreased. We found that YM158 had greater propensity to adapt to low light compared with ZM9023, as the former was able to increase photochemical electron transfer rate, enhance photosystem activity, and increase the light energy under low light. This meant that the YM158 flag leaf has stronger regulatory mechanism under low light environment. Through proteomic analysis, we found LHC protein (LHCB1, LHCB4, LHCA2, LHCA3) for YH158 was significantly up-regulated, while the PSII subunit protein of FM1228 and ZM9023 b559 subunit protein were down-regulated. We also documented enhanced light use efficiency (LUE) due to higher light capture pigment protein complex (LHC), photosystem II (PSII), PSI and cytochrome B6F-related proteins, with dry matter accumulation being positively correlated with Fv/Fm, ETR, and ΦPS(II), and negatively correlated with initial fluorescence F0. We suggest that Fv/Fm, ETR, and ΦPS(II) could be considered in shade tolerance screening to facilitate wheat breeding.

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Violin, Kalan Bastos, Christiane Ribeiro, Tamiye Simone Goia, José Carlos Bressiani et Ana Helena de Almeida Bressiani. « Lectinhistochemistry Evaluation of Rabbits Tibia Implanted with Macroporous Biphasic Ceramic Implants ». Key Engineering Materials 529-530 (novembre 2012) : 331–36. http://dx.doi.org/10.4028/www.scientific.net/kem.529-530.331.

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Many techniques are used to assess biomaterials implants, always intending to measure osseointegration success and tissue response facing the implanted material. Calcium phosphates are widely used as biomaterial and a major component of bone. Many processing methods have been used to achieve porous materials to allow bone ingrowth with an osteoconductive scaffold for bone. To obtain the macroporous BCP implant it was processed by direct consolidation using the protein-action technique, a globular protein based consolidation with ovalbumin. The samples were sintered at 1250°C for 30 minutes, after sintering samples were cut in 4mm diameter cylinders, with 73% volume of porosity and mean pore size ranging about 100 µm. In the present work the macroporous BCP of HAp:β-TCP is assessed after bone implantation in rabbits tibia by lectinhistochemistry (LHC) technique. Lectins are proteins from non-imune origin which binds with strong specificity carbohydrates, LHC is a technique which mark histologically carbohydrates present in glycoproteins of cells. The macroporous BCP cylindrical samples were implanted in male rabbits tibia to the evaluation of biocompatibility and osseointegration in a period of 2 weeks to 4 weeks. After euthanasia of rabbits, tibia samples from the surgery site were taken and fixed with formalin, decalcified, dehydrated and embedded with paraffin to perform histological slides for both morphological and molecular evaluation. The morphological evaluation were performed on histological slides stained with Haematoxilin and Eosin (HE), while for molecular evaluation LHC was performed on histological slides using the lectins PNA, UEA-1, WGA, sWGA and RCA-1 (Vector Labs). All samples osseointegrated well with the bone and the neoformed bone surrounding the implant took the shape of its surface. The implants also allowed bone ingrowth inside the pores towards the center of implant, characterized by islets of round bone present in the HE stained slides.

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Kühlbrandt, Werner, Da Neng Wang et K. H. Downing. « High-Resolution electron crystallography of the light-harvesting chlorophyll-a/b protein complex from chloroplast membranes ». Proceedings, annual meeting, Electron Microscopy Society of America 48, n^o 1 (12 août 1990) : 610. http://dx.doi.org/10.1017/s0424820100181816.

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The light-harvesting chlorophyll-a/b protein complex (LHC-II) is the most abundant membrane protein in the chloroplasts of green plants where it functions as a molecular antenna of solar energy for photosynthesis. We have grown two-dimensional (2d) crystals of the purified, detergent-solubilized LHC-II . The crystals which measured 5 to 10 μm in diameter were stabilized for electron microscopy by washing with a 0.5% solution of tannin. Electron diffraction patterns of untilted 2d crystals cooled to 130 K showed sharp spots to 3.1 Å resolution. Spot-scan images of 2d crystals were recorded at 160 K with the Berkeley microscope . Images of untilted crystals were processed, using the unbending procedure by Henderson et al . A projection map of the complex at 3.7Å resolution was generated from electron diffraction amplitudes and high-resolution phases obtained by image processing .A difference Fourier analysis with the same image phases and electron diffraction amplitudes recorded of frozen, hydrated specimens showed no significant differences in the 3.7Å projection map. Our tannin treatment therefore does not affect the structural integrity of the complex.

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Kohorn, B. D., E. Harel, P. R. Chitnis, J. P. Thornber et E. M. Tobin. « Functional and mutational analysis of the light-harvesting chlorophyll a/b protein of thylakoid membranes. » Journal of Cell Biology 102, n^o 3 (1 mars 1986) : 972–81. http://dx.doi.org/10.1083/jcb.102.3.972.

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The precursor for a Lemna light-harvesting chlorophyll a/b protein (pLHCP) has been synthesized in vitro from a single member of the nuclear LHCP multigene family. We report the sequence of this gene. When incubated with Lemna chloroplasts, the pLHCP is imported and processed into several polypeptides, and the mature form is assembled into the light-harvesting complex of photosystem II (LHC II). The accumulation of the processed LHCP is enhanced by the addition to the chloroplasts of a precursor and a co-factor for chlorophyll biosynthesis. Using a model for the arrangement of the mature polypeptide in the thylakoid membrane as a guide, we have created mutations that lie within the mature coding region. We have studied the processing, the integration into thylakoid membranes, and the assembly into light-harvesting complexes of six of these deletions. Four different mutant LHCPs are found as processed proteins in the thylakoid membrane, but only one appears to have an orientation in the membrane that is similar to that of the wild type. No mutant LHCP appears in LHC II. The other two mutant LHCPs cannot be detected within the chloroplasts. We conclude that stable complex formation is not required for the processing and insertion of altered LHCPs into the thylakoid membrane. We discuss the results in light of our model.

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Proctor, Matthew S., Marek Pazderník, Philip J. Jackson, Jan Pilný, Elizabeth C. Martin, Mark J. Dickman, Daniel P. Canniffe et al. « Xanthophyll carotenoids stabilise the association of cyanobacterial chlorophyll synthase with the LHC-like protein HliD ». Biochemical Journal 477, n^o 20 (29 octobre 2020) : 4021–36. http://dx.doi.org/10.1042/bcj20200561.

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Chlorophyll synthase (ChlG) catalyses a terminal reaction in the chlorophyll biosynthesis pathway, attachment of phytol or geranylgeraniol to the C17 propionate of chlorophyllide. Cyanobacterial ChlG forms a stable complex with high light-inducible protein D (HliD), a small single-helix protein homologous to the third transmembrane helix of plant light-harvesting complexes (LHCs). The ChlG–HliD assembly binds chlorophyll, β-carotene, zeaxanthin and myxoxanthophyll and associates with the YidC insertase, most likely to facilitate incorporation of chlorophyll into translated photosystem apoproteins. HliD independently coordinates chlorophyll and β-carotene but the role of the xanthophylls, which appear to be exclusive to the core ChlG–HliD assembly, is unclear. Here we generated mutants of Synechocystis sp. PCC 6803 lacking specific combinations of carotenoids or HliD in a background with FLAG- or His-tagged ChlG. Immunoprecipitation experiments and analysis of isolated membranes demonstrate that the absence of zeaxanthin and myxoxanthophyll significantly weakens the interaction between HliD and ChlG. ChlG alone does not bind carotenoids and accumulation of the chlorophyllide substrate in the absence of xanthophylls indicates that activity/stability of the ‘naked’ enzyme is perturbed. In contrast, the interaction of HliD with a second partner, the photosystem II assembly factor Ycf39, is preserved in the absence of xanthophylls. We propose that xanthophylls are required for the stable association of ChlG and HliD, acting as a ‘molecular glue’ at the lateral transmembrane interface between these proteins; roles for zeaxanthin and myxoxanthophyll in ChlG–HliD complexation are discussed, as well as the possible presence of similar complexes between LHC-like proteins and chlorophyll biosynthesis enzymes in plants.

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Wu, Guangxi, Lin Ma, Cai Yuan, Jiahao Dai, Lai Luo, Roshan Sharma Poudyal, Richard T. Sayre et Choon-Hwan Lee. « Formation of light-harvesting complex II aggregates from LHCII–PSI–LHCI complexes in rice plants under high light ». Journal of Experimental Botany 72, n^o 13 (3 mai 2021) : 4938–48. http://dx.doi.org/10.1093/jxb/erab188.

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Abstract During low light- (LL) induced state transitions in dark-adapted rice (Oryza sativa) leaves, light-harvesting complex (LHC) II become phosphorylated and associate with PSI complexes to form LHCII–PSI–LHCI supercomplexes. When the leaves are subsequently transferred to high light (HL) conditions, phosphorylated LHCII complexes are no longer phosphorylated. Under the HL-induced transition in LHC phosphorylation status, we observed a new green band in the stacking gel of native green–PAGE, which was determined to be LHCII aggregates by immunoblotting and 77K chlorophyll fluorescence analysis. Knockout mutants of protein phosphatase 1 (PPH1) which dephosphorylates LHCII failed to form these LHCII aggregates. In addition, the ability to develop non-photochemical quenching in the PPH1 mutant under HL was less than for wild-type plants. As determined by immunoblotting analysis, LHCII proteins present in LHCII–PSI–LHCI supercomplexes included the Lhcb1 and Lhcb2 proteins. In this study, we provide evidence suggesting that LHCII in the LHCII–PSI–LHCI supercomplexes are dephosphorylated and subsequently form aggregates to dissipate excess light energy under HL conditions. We propose that this LHCII aggregation, involving LHCII L-trimers, is a newly observed photoprotective light-quenching process operating in the early stage of acclimation to HL in rice plants.

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Ke, Shanqiang, Chiwon W. Lee et Murray E. Duysen. « Influence of the rolC Gene on Proteins Associated with Stroma and Thylakoid Membranes of Chloroplasts in Transgenic Plants of Kentucky Bluegrass ». HortScience 32, n^o 3 (juin 1997) : 482D—482. http://dx.doi.org/10.21273/hortsci.32.3.482d.

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The effects of the expression of the rolC gene on protein accumulation in the chloroplasts of transgenic Kentucky bluegrass (Poa pratensis L.) were investigated. Coleoptile tissues excised from 3-day dark-grown seedlings were bombarded with tungsten particles coated with DNA of the engineered plasmid, pGA-GUSGF, containing the npt II, gus, and rolC genes. The tissues were cultured on callus induction medium, which consists of MS salts supplemented with 0.2 mg/L picloram, 0.01 mg/L naphthaleneacetic acid (NAA) 250 mg/L kanamycin, and 100 mM acetosyringone. The putative transformants were either albinos or variegated plants composed of white and green sections. These albino plants had little or no stroma-based 56-kDa and 14-kDa subunits of the suspected Rubisco proteins, which are expressed in response to genes in the nucleus and plastid, respectively. The albino plants also lacked the 110-kDa and 57–58-kDa, and 43, 47-kDa polypeptides in PS I, coupling factor, and PS II in thylakoid membranes, respectively. These proteins involved in photosynthesis are translated from plastidbased genes. No light-harvesting complex proteins (LHC) were observed in these albino plants. LHC genes are encoded in the nucleus. The thylakoid membrane proteins in the chloroplasts of the rolC transgenic variegated plants contained these proteins. Our data suggest that the nucleus and plastid gene products for plastid development are concomitantly impaired by expression of genes in the transgenic plants.

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Thaler, Thomas, et Frances A. Jay. « Monoclonal antibodies specific for the light-harvesting chlorophyll a/b -protein complex (LHC) ». FEBS Letters 188, n^o 1 (19 août 1985) : 21–26. http://dx.doi.org/10.1016/0014-5793(85)80867-x.

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Klimmek, Frank, Andreas Sjödin, Christos Noutsos, Dario Leister et Stefan Jansson. « Abundantly and Rarely Expressed Lhc Protein Genes Exhibit Distinct Regulation Patterns in Plants ». Plant Physiology 140, n^o 3 (mars 2006) : 793–804. http://dx.doi.org/10.1104/pp.105.073304.

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Fujiyoshi, Y., K. Murata, K. Mitsuoka, T. Hirai, A. Miyazawa et Y. Kimura. « A microscopic system for high-resolution electron crystallography ». Proceedings, annual meeting, Electron Microscopy Society of America 53 (13 août 1995) : 70–71. http://dx.doi.org/10.1017/s0424820100136726.

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High-resolution electron cryo-microscopy is one of good candidate for structure analysis of membrane-protein, and also actually analyzed the structure of membrane-proteins such as bacteriorhodopsin (bR) and plant light-harvesting complex (LHC). By developing an expeditious method for structure analysis up to atomic or near atomic resolution, we would like to interpret a function of protein from the structural point of view. However, there are some difficulties in electron microscopy for structure analysis of protein. Especially, the most serious problems are the specimen damage caused by electron irradiation, the denaturation of biomolecules caused by dehydration and missing high-resolution data on electron micrographs at high-tilted angle.The irradiation damage at 8K has been found to be reduced to 1/20 compared with that at room temperature. We have, therefore, developed a high-resolution electron cryo-microscope and improved it by which images can be recorded with higher resolution than 3 Å at a specimen-stage temperature of 4.2 K, even when the specimen is highly tilted. The highly tilted data are essential for reduction of the missing corn effect.

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Breitholtz, Hanna-Leena, Renu Srivastava, Esa Tyystjärvi et Eevi Rintamäki. « LHC II protein phosphorylation in leaves of Arabidopsis thaliana mutants deficient in non-photochemical quenching ». Photosynthesis Research 84, n^o 1-3 (juin 2005) : 217–23. http://dx.doi.org/10.1007/s11120-005-0998-1.

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Alomrani, Sarah, Karl J. Kunert et Christine H. Foyer. « Papain-like cysteine proteases are required for the regulation of photosynthetic gene expression and acclimation to high light stress ». Journal of Experimental Botany 72, n^o 9 (4 mars 2021) : 3441–54. http://dx.doi.org/10.1093/jxb/erab101.

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AbstractChloroplasts are considered to be devoid of cysteine proteases. Using transgenic Arabidopsis lines expressing the rice cystatin, oryzacystatin I (OC-I), in the chloroplasts (PC lines) or cytosol (CYS lines), we explored the hypothesis that cysteine proteases regulate photosynthesis. The CYS and PC lines flowered later than the wild type (WT) and accumulated more biomass after flowering. In contrast to the PC rosettes, which accumulated more leaf chlorophyll and carotenoid pigments than the WT, the CYS lines had lower amounts of leaf pigments. High-light-dependent decreases in photosynthetic carbon assimilation and the abundance of the Rubisco large subunit protein, the D1 protein, and the phosphorylated form of D1 proteins were attenuated in the CYS lines and reversed in the PC lines relative to the WT. However, the transgenic lines had higher amounts of LHC, rbcs, pasbA, and pasbD transcripts than the WT, and also showed modified chloroplast to nucleus signalling. We conclude that cysteine proteases accelerate the reconfiguration of the chloroplast proteome after flowering and in response to high-light stress. Inhibition of cysteine proteases, such as AtCEP1, slows chloroplast protein degradation and stimulates photosynthetic gene expression and chloroplast to nucleus signalling, enhancing stress tolerance traits.

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Kuryanchyk, T. G., et N. V. Kozel. « GENE EXPRESSION AND THE CONTENT OF STRUCTURAL PROTEINS ; OF PHOTOSYSTEMS IN BARLEY LEAVES UNDER SOIL DROUGHT ». Молекулярная и прикладная генетика 33 (12 novembre 2022) : 38–46. http://dx.doi.org/10.47612/1999-9127-2022-33-38-46.

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A significant effect of soil drought on the gene expression (psaA, psaB, lhca2, psbA, lhcb1 and lhcb4) encoding key structural proteins of reaction centers (RC) and light harvesting complexes (LHC) of photosystems (PS) in barley leaves was shown. A change in the level of gene expression observed under drought conditions is light-dependent — in normal light, there is a significant increase in the expression of lhcb1 (1.6 times), psaA (1.8 times) and psaB (2.5 times) genes, encoding PS I and II proteins, and in the dim light, on the contrary, there is a decrease in the expression of genes encoding the proteins PS II (psbA, lhcb1 and lhcb4) and protein A (psaA) of the PS I RC. It was found that under drought conditions the expression of the gene SOD3 encoding the chloroplast isoform of the antioxidant superoxide dismutase (SOD) enzyme Fe-SOD increases multiple times. The data obtained indicate the induction of oxidative stress by drought in the chloroplasts of the leaves of barley plants.

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Grebe, Steffen, Andrea Trotta, Azfar A. Bajwa, Marjaana Suorsa, Peter J. Gollan, Stefan Jansson, Mikko Tikkanen et Eva-Mari Aro. « The unique photosynthetic apparatus of Pinaceae : analysis of photosynthetic complexes in Picea abies ». Journal of Experimental Botany 70, n^o 12 (2 avril 2019) : 3211–25. http://dx.doi.org/10.1093/jxb/erz127.

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Abstract Pinaceae are the predominant photosynthetic species in boreal forests, but so far no detailed description of the protein components of the photosynthetic apparatus of these gymnosperms has been available. In this study we report a detailed characterization of the thylakoid photosynthetic machinery of Norway spruce (Picea abies (L.) Karst). We first customized a spruce thylakoid protein database from translated transcript sequences combined with existing protein sequences derived from gene models, which enabled reliable tandem mass spectrometry identification of P. abies thylakoid proteins from two-dimensional large pore blue-native/SDS-PAGE. This allowed a direct comparison of the two-dimensional protein map of thylakoid protein complexes from P. abies with the model angiosperm Arabidopsis thaliana. Although the subunit composition of P. abies core PSI and PSII complexes is largely similar to that of Arabidopsis, there was a high abundance of a smaller PSI subcomplex, closely resembling the assembly intermediate PSI* complex. In addition, the evolutionary distribution of light-harvesting complex (LHC) family members of Pinaceae was compared in silico with other land plants, revealing that P. abies and other Pinaceae (also Gnetaceae and Welwitschiaceae) have lost LHCB4, but retained LHCB8 (formerly called LHCB4.3). The findings reported here show the composition of the photosynthetic apparatus of P. abies and other Pinaceae members to be unique among land plants.

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Hidayati, Ernin, Ika Nurhimaya, Nisful Mahdi et Sarkono Sarkono. « Kajian bakteri proteolitik yang diisolasi dari tubuh lalat hijau (Chrysomya megacephala) ». Jurnal Biologi Udayana 26, n^o 2 (28 décembre 2022) : 260. http://dx.doi.org/10.24843/jbiounud.2022.v26.i02.p11.

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Lalat hijau (Chrysomya megacephala) merupakan serangga yang memiliki peranan ekologis penting, salah satu diantaranya adalah sebagai dekomposer. Lalat hijau sering ditemukan berkerumun di sekitar makanan dan sampah yang mengandung protein tinggi. Hinggapnya lalat ini pada makanan perlu diwaspadai karena dapat mengakibatkan makanan lebih cepat rusak atau basi. Diduga bahwa bakteri yang ada pada tubuh lalat berperan dalam proses dekomposisi bahan makanan tersebut. Penelitian ini bertujuan untuk mempelajari bakteri proteolitik yang diisolasi dari tubuh lalat hijau. Sampel lalat hijau diambil dari tempat pembuangan sampah di Kebon Kongok, Lombok Barat, Indonesia. Sampel dimasukkan ke dalam Brain Heart Infusion Broth, selanjutnya bakteri yang terdapat pada tubuh lalat hijau diisolasi menggunakan Nutrient Agar. Aktivitas proteolitik isolat bakteri dideteksi dari terbentuknya zona bening pada medium Skim Milk Agar dengan metode totol dan difusi sumuran. Isolat bakteri kemudian dikarakterisasi melalui pengecatan Gram dan uji biokimia. Ditemukan sebanyak empat isolat bakteri proteolitik pada tubuh lalat hijau yaitu isolat LH1, LH2, LH3 dan LH4. Isolat LH2 menunjukkan aktivitas katalitik paling baik dengan rerata diameter zona bening sebesar 25,5 mm setelah inkubasi 48 jam pada suhu 37oC. LH2 merupakan Gram negatif berbentuk batang rantai pendek, bersifat motil dan aerob. Bakteri ini mampu memanfaatkan beberapa jenis gula seperti arabinosa, sukrosa, maltosa, dan manitol, mampu mengoksidasi asam amino triptofan serta mampu mengubah urea menjadi amonia. Hasil penelitian ini memberikan informasi bahwa, LH2 berkontribusi dalam proses dekomposisi. Selain itu, LH2 juga berpotensi sebagai patogen.

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Gillbro, Tomas, Villy Sundström, Åke Sandström, Michael Spangfort et Bertil Andersson. « Energy transfer within the isolated light-harvesting chlorophyll a/b protein of photosystem II (LHC-II) ». FEBS Letters 193, n^o 2 (2 décembre 1985) : 267–70. http://dx.doi.org/10.1016/0014-5793(85)80166-6.

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Xiaonan, Wu, Zhou Baicheng et C. K. Tseng. « Polyclonal antibodies to light-harvesting CHL-protein of PSII (LHC II) in marine green algaeBryopsis corticulans ». Chinese Journal of Oceanology and Limnology 10, n^o 2 (juin 1992) : 135–44. http://dx.doi.org/10.1007/bf02844744.

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Mey, Jacob T., Brian K. Blackburn, Edwin R. Miranda, Alec B. Chaves, Joan Briller, Marcelo G. Bonini et Jacob M. Haus. « Dicarbonyl stress and glyoxalase enzyme system regulation in human skeletal muscle ». American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 314, n^o 2 (1 février 2018) : R181—R190. http://dx.doi.org/10.1152/ajpregu.00159.2017.

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Skeletal muscle insulin resistance is a hallmark of Type 2 diabetes (T2DM) and may be exacerbated by protein modifications by methylglyoxal (MG), known as dicarbonyl stress. The glyoxalase enzyme system composed of glyoxalase 1/2 (GLO1/GLO2) is the natural defense against dicarbonyl stress, yet its protein expression, activity, and regulation remain largely unexplored in skeletal muscle. Therefore, this study investigated dicarbonyl stress and the glyoxalase enzyme system in the skeletal muscle of subjects with T2DM (age: 56 ± 5 yr.; BMI: 32 ± 2 kg/m2) compared with lean healthy control subjects (LHC; age: 27 ± 1 yr.; BMI: 22 ± 1 kg/m2). Skeletal muscle biopsies obtained from the vastus lateralis at basal and insulin-stimulated states of the hyperinsulinemic (40 mU·m−2·min−1)–euglycemic (5 mM) clamp were analyzed for proteins related to dicarbonyl stress and glyoxalase biology. At baseline, T2DM had increased carbonyl stress and lower GLO1 protein expression (−78.8%), which inversely correlated with BMI, percent body fat, and HOMA-IR, while positively correlating with clamp-derived glucose disposal rates. T2DM also had lower NRF2 protein expression (−31.6%), which is a positive regulator of GLO1, while Keap1 protein expression, a negative regulator of GLO1, was elevated (207%). Additionally, insulin stimulation during the clamp had a differential effect on NRF2, Keap1, and MG-modified protein expression. These data suggest that dicarbonyl stress and the glyoxalase enzyme system are dysregulated in T2DM skeletal muscle and may underlie skeletal muscle insulin resistance. Whether these phenotypic differences contribute to the development of T2DM warrants further investigation.

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Stauber, Einar J., Andreas Fink, Christine Markert, Olaf Kruse, Udo Johanningmeier et Michael Hippler. « Proteomics of Chlamydomonas reinhardtii Light-Harvesting Proteins ». Eukaryotic Cell 2, n^o 5 (octobre 2003) : 978–94. http://dx.doi.org/10.1128/ec.2.5.978-994.2003.

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ABSTRACT With the recent development of techniques for analyzing transmembrane thylakoid proteins by two-dimensional gel electrophoresis, systematic approaches for proteomic analyses of membrane proteins became feasible. In this study, we established detailed two-dimensional protein maps of Chlamydomonas reinhardtii light-harvesting proteins (Lhca and Lhcb) by extensive tandem mass spectrometric analysis. We predicted eight distinct Lhcb proteins. Although the major Lhcb proteins were highly similar, we identified peptides which were unique for specific lhcbm gene products. Interestingly, lhcbm6 gene products were resolved as multiple spots with different masses and isoelectric points. Gene tagging experiments confirmed the presence of differentially N-terminally processed Lhcbm6 proteins. The mass spectrometric data also revealed differentially N-terminally processed forms of Lhcbm3 and phosphorylation of a threonine residue in the N terminus. The N-terminal processing of Lhcbm3 leads to the removal of the phosphorylation site, indicating a potential novel regulatory mechanism. At least nine different lhca-related gene products were predicted by comparison of the mass spectrometric data against Chlamydomonas expressed sequence tag and genomic databases, demonstrating the extensive variability of the C. reinhardtii Lhca antenna system. Out of these nine, three were identified for the first time at the protein level. This proteomic study demonstrates the complexity of the light-harvesting proteins at the protein level in C. reinhardtii and will be an important basis of future functional studies addressing this diversity.

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Hemelrijk, Petra W., Stefan L. S. Kwa, Rienk van Grondelle et Jan P. Dekker. « Spectroscopic properties of LHC-II, the main light-harvesting chlorophyll a/b protein complex from chloroplast membranes ». Biochimica et Biophysica Acta (BBA) - Bioenergetics 1098, n^o 2 (janvier 1992) : 159–66. http://dx.doi.org/10.1016/s0005-2728(05)80331-7.

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Mullineaux, Conrad W. « Excitation energy quenching in aggregates of the LHC II chlorophyll-protein complex : A laser-induced optoacoustic study ». Biochimica et Biophysica Acta (BBA) - Bioenergetics 1143, n^o 2 (juillet 1993) : 235–38. http://dx.doi.org/10.1016/0005-2728(93)90148-9.

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Mullineaux, Conrad W., Andrew A. Pascal, Peter Horton et Alfred R. Holzwarth. « Excitation-energy quenching in aggregates of the LHC II chlorophyll-protein complex : a time-resolved fluorescence study ». Biochimica et Biophysica Acta (BBA) - Bioenergetics 1141, n^o 1 (février 1993) : 23–28. http://dx.doi.org/10.1016/0005-2728(93)90184-h.

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Baker, Lewis A., et Scott Habershon. « Photosynthetic pigment-protein complexes as highly connected networks : implications for robust energy transport ». Proceedings of the Royal Society A : Mathematical, Physical and Engineering Sciences 473, n^o 2201 (mai 2017) : 20170112. http://dx.doi.org/10.1098/rspa.2017.0112.

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Photosynthetic pigment-protein complexes (PPCs) are a vital component of the light-harvesting machinery of all plants and photosynthesizing bacteria, enabling efficient transport of the energy of absorbed light towards the reaction centre, where chemical energy storage is initiated. PPCs comprise a set of chromophore molecules, typically bacteriochlorophyll species, held in a well-defined arrangement by a protein scaffold; this relatively rigid distribution leads to a viewpoint in which the chromophore subsystem is treated as a network, where chromophores represent vertices and inter-chromophore electronic couplings represent edges. This graph-based view can then be used as a framework within which to interrogate the role of structural and electronic organization in PPCs. Here, we use this network-based viewpoint to compare excitation energy transfer (EET) dynamics in the light-harvesting complex II (LHC-II) system commonly found in higher plants and the Fenna-Matthews-Olson (FMO) complex found in green sulfur bacteria. The results of our simple network-based investigations clearly demonstrate the role of network connectivity and multiple EET pathways on the efficient and robust EET dynamics in these PPCs, and highlight a role for such considerations in the development of new artificial light-harvesting systems.

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Bradburne, James A., Michael J. Kasperbauer et James N. Mathis. « Reflected Far-Red Light Effects on Chlorophyll and Light-Harvesting Chlorophyll Protein (LHC-II) Contents under Field Conditions ». Plant Physiology 91, n^o 3 (1 novembre 1989) : 800–803. http://dx.doi.org/10.1104/pp.91.3.800.

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ISLAM, KHALID. « ATP-induced fluorescence decline and phosphorylation of the light-harvesting chlorophyll a/b binding protein complex (LHC-II) protein at low and high ATP concentrations ». Biochemical Society Transactions 16, n^o 1 (1 février 1988) : 46–47. http://dx.doi.org/10.1042/bst0160046.

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Kühlbrandt, Werner. « Image Processing of Thin Three-Dimensional Crystals of the Light-Harvesting Chlorophyll a/b-Protein Complex from Chloroplast Membranes ». Proceedings, annual meeting, Electron Microscopy Society of America 46 (1988) : 148–49. http://dx.doi.org/10.1017/s0424820100102821.

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Thin three-dimensional, hexagonal crystals of the light—harvesting chlorophyll a/b—protein complex (LHC II) from pea chloroplast membranes diffract electrons to 3.7 Å resolution when preserved in glucose or tannin. The symmetry of the diffraction pattern (6mm), the dimensions of the unit cell in projection (a = 127 Å) and micrographs of negatively stained specimens suggested that the hexagonal crystals were stacks of two-dimensional crystals of p321 symmetry. Low—dose (1 —2 electrons/Å2) electron micrographs of thin three-dimensional crystals preserved in tannin were recorded in an attempt to determine the structure of this integral membrane protein complex at high resolution, initially in projection. The best images showed sharp diffraction spots at 12 — 14 Å resolution when examined by optical diffraction. Image areas measuring up to 40 x 40 mm2 were densitometered at a step size corresponding to 3 Å or less at the specimen and computer processed to correct for lattice distortions, using programmes by R.Henderson and J.M.Baldwin. Fourier transforms of the distortion—corrected images showed reflections above background level to 6 Å resolution.

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Alexander, Laura, Denis Falconet, Brian W. Fristensky, Michael J. White, John C. Watson, Bruce A. Roe et William F. Thompson. « Nucleotide sequence ofCab-8, a new type I gene encoding a chlorophylla/b-binding protein of LHC II inPisum ». Plant Molecular Biology 17, n^o 3 (septembre 1991) : 523–26. http://dx.doi.org/10.1007/bf00040649.

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Girolomoni, Laura, Stefano Cazzaniga, Alberta Pinnola, Federico Perozeni, Matteo Ballottari et Roberto Bassi. « LHCSR3 is a nonphotochemical quencher of both photosystems inChlamydomonas reinhardtii ». Proceedings of the National Academy of Sciences 116, n^o 10 (19 février 2019) : 4212–17. http://dx.doi.org/10.1073/pnas.1809812116.

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Photosynthetic organisms prevent oxidative stress from light energy absorbed in excess through several photoprotective mechanisms. A major component is thermal dissipation of chlorophyll singlet excited states and is called nonphotochemical quenching (NPQ). NPQ is catalyzed in green algae by protein subunits called LHCSRs (Light Harvesting Complex Stress Related), homologous to the Light Harvesting Complexes (LHC), constituting the antenna system of both photosystem I (PSI) and PSII. We investigated the role of LHCSR1 and LHCSR3 in NPQ activation to verify whether these proteins are involved in thermal dissipation of PSI excitation energy, in addition to their well-known effect on PSII. To this aim, we measured the fluorescence emitted at 77 K by whole cells in a quenched or unquenched state, using green fluorescence protein as the internal standard. We show that NPQ activation by high light treatment inChlamydomonas reinhardtiileads to energy quenching in both PSI and PSII antenna systems. By analyzing quenching properties of mutants affected on the expression of LHCSR1 or LHCSR3 gene products and/or state 1–state 2 transitions or zeaxanthin accumulation, namely,npq4,stt7,stt7 npq4,npq4 lhcsr1,lhcsr3-complementednpq4 lhcsr1andnpq1, we showed that PSI undergoes NPQ through quenching of the associated LHCII antenna. This quenching event is fast-reversible on switching the light off, is mainly related to LHCSR3 activity, and is dependent on thylakoid luminal pH. Moreover, PSI quenching could also be observed in the absence of zeaxanthin or STT7 kinase activity.

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Hinshaw, J. E., et K. R. Miller. « Localization of light-harvesting complex II to the occluded surfaces of photosynthetic membranes. » Journal of Cell Biology 109, n^o 4 (1 octobre 1989) : 1725–31. http://dx.doi.org/10.1083/jcb.109.4.1725.

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The photosynthetic membranes of green plants are organized into stacked regions interconnected by nonstacked regions that have been shown to be biochemically and structurally distinct. Because the stacking process occludes the surfaces of appressed membranes, it has been impossible to conduct structural or biochemical studies of the outer surfaces of the photosynthetic membrane in regions of membrane stacking. Although stacking is mediated at this surface, it has not been possible to determine whether membrane components implicated in the stacking process, including a major light-harvesting complex (LHC-II), are in fact exposed at the membrane surface. We have been able to expose this surface for study in the electron microscope and directly label it with antibodies to determine protein exposure. The appearance of the newly exposed outer stacked surface highlights the extreme lateral heterogeneity of the photosynthetic membrane. The surface is smooth in contrast to the neighboring nonstacked surface that is covered with distinct particles. Although some investigators have suggested the existence of a cytochrome b6/f-rich boundary region between stacked and nonstacked membranes, our results provide no structural support for this concept. To explore the biochemical nature of the occluded membrane surface, we have used an mAb against the amino terminal region of the LHC-II. This mAb clearly labels the newly exposed outer stacked surface but does not label the inner surface or the outer nonstacked surface. These experimental results confirm the presence of the amino terminal region of this complex at the outer surface of the membrane in stacked regions, and also show that this complex is largely absent from nonstacked membranes.

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Vechtel, Burkhard, Elfriede K. Pistorius et Hans Georg Ruppel. « Occurrence of Secondary Carotenoids in PS I Complexes Isolated from Eremosphaera viridis De Bary (Chlorophyceae) ». Zeitschrift für Naturforschung C 47, n^o 1-2 (1 février 1992) : 51–56. http://dx.doi.org/10.1515/znc-1992-1-210.

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Abstract Photosystem I complexes of Eremosphaera viridis De Bary (Chlorophyceae, Chlorococcales) were isolated and partially characterized. In the isolated PS I complexes, peptides of 64-60, 26, 23, 20, 15, 11 and 8.5 kDa could be detected. When Eremosphaera was grown under regular conditions the pigment composition of the isolated PS I complexes was similar to that found in PS I complexes from other green algae. However, when Eremosphaera was grown under nitrogen deficient conditions, PS I complexes contained the secondary carotenoids canthaxanthin and traces of astaxanthin and echinenone in addition to β-carotene, violaxanthin and lutein. The results presented indicate that the secondary carotenoids are associated with the LHC I of PS I. To our knowledge this represents the first report about the association of secondary carotenoids with light harvesting pigment protein complexes of green algae.

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Garczarek, Laurence, Anne Poupon et FrÃ©dÃ©ric Partensky. « Origin and evolution of transmembrane Chl-binding proteins : hydrophobic cluster analysis suggests a common one-helix ancestor for prokaryotic (Pcb) and eukaryotic (LHC) antenna protein superfamilies ». FEMS Microbiology Letters 222, n^o 1 (mai 2003) : 59–68. http://dx.doi.org/10.1016/s0378-1097(03)00241-6.

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Jackowski, Grzegorz, Karol Kacprzak et Stefan Jansson. « Identification of Lhcb1/Lhcb2/Lhcb3 heterotrimers of the main light-harvesting chlorophyll a/b–protein complex of Photosystem II (LHC II) ». Biochimica et Biophysica Acta (BBA) - Bioenergetics 1504, n^o 2-3 (avril 2001) : 340–45. http://dx.doi.org/10.1016/s0005-2728(00)00262-0.

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