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Thylakoids

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https://www.readbyqxmd.com/read/28237493/low-ph-induced-reversible-reorganizations-of-chloroplast-thylakoid-membranes-as-revealed-by-small-angle-neutron-scattering
#1
Renáta Ünnep, Ottó Zsiros, Zsolt Hörcsik, Márton Markó, Anjana Jajoo, Joachim Kohlbrecher, Győző Garab, Gergely Nagy
Energization of thylakoid membranes brings about the acidification of the lumenal aqueous phase, which activates important regulatory mechanisms. Earlier Jajoo and coworkers (2014 FEBS Lett. 588:970) have shown that low pH in isolated plant thylakoid membranes induces changes in the excitation energy distribution between the two photosystems. In order to elucidate the structural background of these changes, we used small-angle neutron scattering on thylakoid membranes exposed to low p(2)H (pD) and show that gradually lowering the p(2)H from 8...
February 22, 2017: Biochimica et Biophysica Acta
https://www.readbyqxmd.com/read/28223511/a-signal-sequence-suppressor-mutant-that-stabilizes-an-assembled-state-of-the-twin-arginine-translocase
#2
Qi Huang, Felicity Alcock, Holger Kneuper, Justin C Deme, Sarah E Rollauer, Susan M Lea, Ben C Berks, Tracy Palmer
The twin-arginine protein translocation (Tat) system mediates transport of folded proteins across the cytoplasmic membrane of bacteria and the thylakoid membrane of chloroplasts. The Tat system of Escherichia coli is made up of TatA, TatB, and TatC components. TatBC comprise the substrate receptor complex, and active Tat translocases are formed by the substrate-induced association of TatA oligomers with this receptor. Proteins are targeted to TatBC by signal peptides containing an essential pair of arginine residues...
February 21, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28219973/sulfoquinovose-in-the-biosphere-occurrence-metabolism-and-functions
#3
REVIEW
Ethan D Goddard-Borger, Spencer J Williams
The sulfonated carbohydrate sulfoquinovose (SQ) is produced in quantities estimated at some 10 billion tonnes annually and is thus a major participant in the global sulfur biocycle. SQ is produced by most photosynthetic organisms and incorporated into the sulfolipid sulfoquinovosyl diacylglycerol (SQDG), as well as within some archaea for incorporation into glycoprotein N-glycans. SQDG is found mainly within the thylakoid membranes of the chloroplast, where it appears to be important for membrane structure and function and for optimal activity of photosynthetic protein complexes...
February 20, 2017: Biochemical Journal
https://www.readbyqxmd.com/read/28213560/identification-of-putative-substrates-of-sec2-a-chloroplast-inner-envelope-translocase
#4
Yubing Li, Jonathan R Martin, Giovanni A Aldama, Donna E Fernandez, Kenneth Cline
Most chloroplast proteins are synthesized in the cytosol and imported into chloroplasts. Many imported proteins are further targeted to the thylakoid membrane and lumen by the SEC1, TAT or SRP/ALB3 translocases. Others are targeted to the inner chloroplast envelope membrane by un-described translocase(s). Recently, a second SEC system (SEC2) consisting of SCY2, SECE2, and SECA2 was found in the chloroplast envelope. Null mutants of SCY2 in Arabidopsis exhibit a severe embryo lethal phenotype. To investigate the function of SEC2 system in plants, we used inducible RNAi to knockdown SCY2 in Arabidopsis...
February 17, 2017: Plant Physiology
https://www.readbyqxmd.com/read/28199209/photosystem-ii-and-terminal-respiratory-oxidases-molecular-machines-operating-in-opposite-directions
#5
Sergey A Siletsky, Vitaliy B Borisov, Mahir D Mamedov
In the thylakoid membrane of green plants, cyanobacteria and algae, photosystem II (PSII) uses light energy to split water and generate molecular oxygen. In the opposite process of the biochemical transformation of dioxygen, in heterotrophs, the terminal respiratory oxidases (TRO) are at the end of the respiratory chain in mitochondria and in plasma membrane of many aerobic bacteria reducing dioxygen back to water. Despite the different sources of free energy (light or oxidation of the substrates), energy conversion by these enzymes is based on the spatial organization of enzymatic reactions in which the conversion of water to dioxygen (and vice versa) involves the transfer of protons and electrons in opposite directions across the membrane, which is accompanied by generation of proton-motive force...
March 1, 2017: Frontiers in Bioscience (Landmark Edition)
https://www.readbyqxmd.com/read/28194920/specific-interaction-between-redox-phospholipid-polymers-and-plastoquinone-in-photosynthetic-electron-transport-chain
#6
Kenya Tanaka, Masahiro Kaneko, Masahito Ishikawa, Souichiro Kato, Hidehiro Ito, Toshiaki Kamachi, Kazuhide Kamiya, Shuji Nakanishi
Redox phospholipid polymers added in culture media are known to be capable of extracting electrons from living photosynthetic cells across bacterial cell membranes with high cytocompatibility. In the present study, we aimed to identify the intracellular redox species that transfers electrons to the polymers. The open-circuit electrochemical potential of an electrolyte containing the redox polymer and extracted thylakoid membranes shifted to positive (or negative) under light irradiation, when an electron transport inhibitor specific for the upstream (or downstream) of plastoquinone in the photosynthetic electron transport chain was added...
February 13, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
https://www.readbyqxmd.com/read/28194795/diversity-of-winter-photoinhibitory-responses-a-case-study-in-co-occurring-lichens-mosses-herbs-and-woody-plants-from-subalpine-environments
#7
Fátima Míguez, Beatriz Fernández-Marín, José-María Becerril, José-Ignacio García-Plazaola
Winter evergreens living in mountainous areas have to withstand a harsh combination of high light levels and low temperatures in wintertime. In response, evergreens can activate a photoprotective process that consists of the down-regulation of photosynthetic efficiency, referred to as winter photoinhibition (WPI). WPI has been studied mainly in woody evergreens and crops even when, in many instances, other functional groups such as lichens or bryophytes dominate in alpine and boreal habitats. Thus, we aimed to (1) assess the occurrence of WPI within overwintering evergreens comprising woody species, herbs, mosses and lichens; (2) compare the recovery kinetics among those groups; and (3) clarify the role of thylakoid proteins and pigments in both processes: WPI and recovery...
February 14, 2017: Physiologia Plantarum
https://www.readbyqxmd.com/read/28188256/mgdg-pg-and-sqdg-regulate-the-activity-of-light-dependent-protochlorophyllide-oxidoreductase
#8
Michal Gabruk, Beata Myśliwa-Kurdziel, Jerzy Kruk
Light-dependent protochlorophyllide oxidoreductase (POR) is a plant enzyme involved in the chlorophyll biosynthesis pathway. POR reduces one of the double bonds of the protochlorophyllide (Pchlide) using NADPH and light. In the present paper, we found out that PG and SQDG are allosteric regulators of the nucleotide binding, which increase the affinity towards NADPH a hundred fold. Moreover, we showed for the first time that NADH can, like NADPH, form active complexes with Pchlide and POR, however at much higher concentrations...
February 10, 2017: Biochemical Journal
https://www.readbyqxmd.com/read/28176001/multilayer-gyroid-cubic-membrane-organization-in-green-alga-zygnema
#9
Ting Zhan, Wenhua Lv, Yuru Deng
Biological cubic membranes (CM), which are fluid membranes draped onto the 3D periodic parallel surface geometries with cubic symmetry, have been observed within subcellular organelles, including mitochondria, endoplasmic reticulum, and thylakoids. CM transition tends to occur under various stress conditions; however, multilayer CM organizations often appear associated with light stress conditions. This report is about the characterization of a projected gyroid CM in a transmission electron microscopy study of the chloroplast membranes within green alga Zygnema (LB923) whose lamellar form of thylakoid membrane started to fold into multilayer gyroid CM in the culture at the end of log phase of cell growth...
February 7, 2017: Protoplasma
https://www.readbyqxmd.com/read/28167950/small-one-helix-proteins-are-essential-for-photosynthesis-in-arabidopsis
#10
Jochen Beck, Jens N Lohscheider, Susanne Albert, Ulrica Andersson, Kurt W Mendgen, Marc C Rojas-Stütz, Iwona Adamska, Dietmar Funck
The extended superfamily of chlorophyll a/b binding proteins comprises the Light-Harvesting Complex Proteins (LHCs), the Early Light-Induced Proteins (ELIPs) and the Photosystem II Subunit S (PSBS). The proteins of the ELIP family were proposed to function in photoprotection or assembly of thylakoid pigment-protein complexes and are further divided into subgroups with one to three transmembrane helices. Two small One-Helix Proteins (OHPs) are expressed constitutively in green plant tissues and their levels increase in response to light stress...
2017: Frontiers in Plant Science
https://www.readbyqxmd.com/read/28167782/ppr-smr-protein-sot1-has-rna-endonuclease-activity
#11
Wen Zhou, Qingtao Lu, Qingwei Li, Lei Wang, Shunhua Ding, Aihong Zhang, Xiaogang Wen, Lixin Zhang, Congming Lu
Numerous attempts have been made to identify and engineer sequence-specific RNA endonucleases, as these would allow for efficient RNA manipulation. However, no natural RNA endonuclease that recognizes RNA in a sequence-specific manner has been described to date. Here, we report that SUPPRESSOR OF THYLAKOID FORMATION 1 (SOT1), an Arabidopsis pentatricopeptide repeat (PPR) protein with a small MutS-related (SMR) domain, has RNA endonuclease activity. We show that the SMR moiety of SOT1 performs the endonucleolytic maturation of 23S and 4...
February 6, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28161893/identification-and-characterization-of-a-stable-intermediate-in-photosystem-i-assembly-in-tobacco
#12
Gal Wittenberg, Sari Järvi, Marta Hojka, Szilvia Z Tóth, Etienne H Meyer, Eva-Mari Aro, Mark Aurel Schöttler, Ralph Bock
PSI is the most efficient bioenergetic nanomachine in nature and one of the largest membrane protein complexes known. It is composed of 18 protein subunits that bind more than 200 co-factors and prosthetic groups. While the structure and function of PSI have been studied in great detail, very little is known about the PSI assembly process. In this work, we have characterized a PSI assembly intermediate in tobacco plants, which we named PSI*. We found PSI* to contain only a specific subset of the core subunits of PSI...
February 5, 2017: Plant Journal: for Cell and Molecular Biology
https://www.readbyqxmd.com/read/28153926/the-synechocystis-manganese-exporter-mnx-is-essential-for-manganese-homeostasis-in-cyanobacteria
#13
Fabian Brandenburg, Hanan Schoffman, Samantha Kurz, Ute Kraemer, Nir Keren, Andreas P M Weber, Marion Eisenhut
The essential micronutrient Manganese (Mn) functions as redox-active cofactor in active sites of enzymes and is thus involved in various physiological reactions. In oxygenic photosynthetic organisms Mn is moreover of special importance, since it is central to the oxygen-evolving complex in photosystem II (PSII). Albeit Mn is an essential micronutrient, increased amounts are detrimental to the organism and thus only a small window exists for beneficial concentrations. Accordingly, Mn homeostasis must be carefully maintained...
January 30, 2017: Plant Physiology
https://www.readbyqxmd.com/read/28153925/the-formation-and-sequestration-of-non-endogenous-ketocarotenoids-in-transgenic-nicotiana-glauca
#14
Cara Louise Mortimer, Norihiko Misawa, Laura Perez-Fons, Francesca Pamela Robertson, Hisashi Harada, Peter M Bramley, Paul David Fraser
Ketolated and hydroxylated carotenoids are high-value compounds with industrial, food and feed applications. Chemical synthesis is presently the production method of choice for these compounds, with no amenable plant sources readily available. In the present study, the 4, 4' β-oxygenase (crtW) and 3, 3' β-hydroxylase (crtZ) genes from Brevundimonas sp SD-212. have been expressed under constitutive transcriptional control in Nicotiana glauca, which has an emerging potential as biofuel and biorefining feedstock...
January 30, 2017: Plant Physiology
https://www.readbyqxmd.com/read/28150587/salicylic-acid-and-ascorbic-acid-retrieve-activity-of-antioxidative-enzymes-and-structure-of-caralluma-tuberculata-calli-on-peg-stress
#15
Riaz U Rehman, Muhammad Zia, Muhammad F Chaudhary
Biochemical adaptations and morphological changes are cellular aptitude originated on biotic and abiotic stresses. Polyethylene glycol (PEG) induces drought stress in the nutrient solution. In the present investigation, Caralluma tuberculata calli is exposed to PEG and antioxidative molecules. By increasing the level of antioxidative enzymes (SOD, POD, CAT, APX, and GR), the PEG-stressed calli falls off upon exposure to non-enzymatic antioxidants (ascorbic acid and salicylic acid). Under PEG-stress, several cellular and sub-cellular changes such as alteration in plasma membrane thickness, change in nucleus shape, increase in nucleoli, deformation of thylakoid membranes, and increase in plastoglobuli are observed through electron microscopic images...
February 2, 2017: General Physiology and Biophysics
https://www.readbyqxmd.com/read/28139457/the-unprecedented-versatility-of-the-plant%C3%A2-thioredoxin-system
#16
REVIEW
Peter Geigenberger, Ina Thormählen, Danilo M Daloso, Alisdair R Fernie
Thioredoxins are ubiquitous enzymes catalyzing reversible disulfide-bond formation to regulate structure and function of many proteins in diverse organisms. In recent years, reverse genetics and biochemical approaches were used to resolve the functions, specificities, and interactions of the different thioredoxin isoforms and reduction systems in planta and revealed the most versatile thioredoxin system of all organisms. Here we review the emerging roles of the thioredoxin system, namely the integration of thylakoid energy transduction, metabolism, gene expression, growth, and development under fluctuating environmental conditions...
March 2017: Trends in Plant Science
https://www.readbyqxmd.com/read/28134919/the-xanthophyll-cycle-affects-reversible-interactions-between-psbs-and-light-harvesting-complex-ii-to-control-non-photochemical-quenching
#17
Joanna Sacharz, Vasco Giovagnetti, Petra Ungerer, Giulia Mastroianni, Alexander V Ruban
To maintain high photosynthetic rates, plants must adapt to their light environment on a timescale of seconds to minutes. Therefore, the light-harvesting antenna system of photosystem II in thylakoid membranes, light-harvesting complex II (LHCII), has a feedback mechanism, which determines the proportion of absorbed energy dissipated as heat: non-photochemical chlorophyll fluorescence quenching (NPQ). This is crucial to prevent photo-oxidative damage to photosystem II (PSII) and is controlled by the transmembrane pH differences (ΔpH)...
January 30, 2017: Nature Plants
https://www.readbyqxmd.com/read/28125283/plastoglobuli-plastid-microcompartments-with-integrated-functions-in-metabolism-plastid-developmental-transitions-and-environmental-adaptation
#18
Klaas J van Wijk, Felix Kessler
Plastoglobuli (PGs) are plastid lipoprotein particles surrounded by a membrane lipid monolayer. PGs contain small specialized proteomes and metabolomes. They are present in different plastid types (e.g., chloroplasts, chromoplasts, and elaioplasts) and are dynamic in size and shape in response to abiotic stress or developmental transitions. PGs in chromoplasts are highly enriched in carotenoid esters and enzymes involved in carotenoid metabolism. PGs in chloroplasts are associated with thylakoids and contain ∼30 core proteins (including six ABC1 kinases) as well as additional proteins recruited under specific conditions...
January 25, 2017: Annual Review of Plant Biology
https://www.readbyqxmd.com/read/28103409/zea-mays-fe-deficiency-related-4-zmfdr4-functions-as-an-iron-transporter-in-the-plastids-of-monocots
#19
Xiu-Yue Zhang, Xi Zhang, Qi Zhang, Xiao-Xi Pan, Luo-Chen Yan, Xiao-Juan Ma, Wei-Zhong Zhao, Xiao-Ting Qi, Li-Ping Yin
Iron (Fe)-homeostasis in the plastids is closely associated with Fe transport proteins that prevent Fe from occurring in its toxic free ionic forms. However, the number of known protein families related to Fe transport in the plastids (about 5) and the function of iron in non-green plastids is limited. In the present study, we report the functional characterization of Zea mays Fe deficiency-related 4 (ZmFDR4), which was isolated from a differentially expressed clone of a cDNA library of Fe deficiency-induced maize roots...
January 19, 2017: Plant Journal: for Cell and Molecular Biology
https://www.readbyqxmd.com/read/28103282/two-novel-vesicle-inducing-proteins-in-plastids-1-genes-cloned-and-characterized-in-triticum-urartu
#20
Fei Gao, Bo Chen, Juan Jiao, Lijia Jia, Cuimin Liu
Vesicle-inducing protein in plastids 1 (Vipp1) is thought to play an important role both in thylakoid biogenesis and chloroplast envelope maintenance during stress. Vipp1 is conserved in photosynthetic organisms and forms a high homo-oligomer complex structure that may help sustain the membrane integrity of chloroplasts. This study cloned two novel VIPP1 genes from Triticum urartu and named them TuVipp1 and TuVipp2. Both proteins shared high identity with the homologous proteins AtVipp1 and CrVipp1. TuVipp1 and TuVipp2 were expressed in various organs of common wheat, and both genes were induced by light and various stress treatments...
2017: PloS One
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