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Allan M Showalter, Brian D Keppler, Xiao Liu, Jens Lichtenberg, Lonnie R Welch
BACKGROUND: Hydroxyproline-rich glycoproteins (HRGPs) constitute a plant cell wall protein superfamily that functions in diverse aspects of growth and development. This superfamily contains three members: the highly glycosylated arabinogalactan-proteins (AGPs), the moderately glycosylated extensins (EXTs), and the lightly glycosylated proline-rich proteins (PRPs). Chimeric and hybrid HRGPs, however, also exist. A bioinformatics approach is employed here to identify and classify AGPs, EXTs, PRPs, chimeric HRGPs, and hybrid HRGPs from the proteins predicted by the completed genome sequence of poplar (Populus trichocarpa)...
October 21, 2016: BMC Plant Biology
David Bína, Zdenko Gardian, Miroslava Herbstová, Radek Litvín
Photosystem I (PSI) is a multi-subunit integral pigment-protein complex that performs light-driven electron transfer from plastocyanin to ferredoxin in the thylakoid membrane of oxygenic photoautotrophs. In order to achieve the optimal photosynthetic performance under ambient irradiance, the absorption cross section of PSI is extended by means of peripheral antenna complexes. In eukaryotes, this role is played mostly by the pigment-protein complexes of the LHC family. The structure of the PSI-antenna supercomplexes has been relatively well understood in organisms harboring the primary plastid: red algae, green algae and plants...
October 12, 2016: Photosynthesis Research
Alessandro Alboresi, Clotilde Le Quiniou, Sathish K N Yadav, Martin Scholz, Andrea Meneghesso, Caterina Gerotto, Diana Simionato, Michael Hippler, Egbert J Boekema, Roberta Croce, Tomas Morosinotto
Photosystem I (PSI) is a pigment protein complex catalyzing the light-driven electron transport from plastocyanin to ferredoxin in oxygenic photosynthetic organisms. Several PSI subunits are highly conserved in cyanobacteria, algae and plants, whereas others are distributed differentially in the various organisms. Here we characterized the structural and functional properties of PSI purified from the heterokont alga Nannochloropsis gaditana, showing that it is organized as a supercomplex including a core complex and an outer antenna, as in plants and other eukaryotic algae...
September 13, 2016: New Phytologist
Yingnan Hou, Xinyang Guo, Philipp Cyprys, Ying Zhang, Andrea Bleckmann, Le Cai, Qingpei Huang, Yu Luo, Hongya Gu, Thomas Dresselhaus, Juan Dong, Li-Jia Qu
During the angiosperm (flowering-plant) life cycle, double fertilization represents the hallmark between diploid and haploid generations [1]. The success of double fertilization largely depends on compatible communication between the male gametophyte (pollen tube) and the maternal tissues of the flower, culminating in precise pollen tube guidance to the female gametophyte (embryo sac) and its rupture to release sperm cells. Several important factors involved in the pollen tube reception have been identified recently [2-6], but the underlying signaling pathways are far from being understood...
September 12, 2016: Current Biology: CB
Emeline Sautron, Cécile Giustini, ThuyVan Dang, Lucas Moyet, Daniel Salvi, Serge Crouzy, Norbert Rolland, Patrice Catty, Daphné Seigneurin-Berny
Copper is an essential transition metal for living organisms. In the plant model Arabidopsis thaliana, half of the copper content is localized in the chloroplast, and as a cofactor of plastocyanin, copper is essential for photosynthesis. Within the chloroplast, copper delivery to plastocyanin involves two transporters of the PIB-1-ATPases subfamily: HMA6 at the chloroplast envelope and HMA8 in the thylakoid membranes. Both proteins are high affinity copper transporters but share distinct enzymatic properties...
September 16, 2016: Journal of Biological Chemistry
I B Kovalenko, S S Khrushchev, V A Fedorov, G Yu Riznichenko, A B Rubin
Electrostatic interaction of plastocyanin and cytochrome f in the process of protein-protein complex formation was investigated by computer simulation methods. It was shown that long-range electrostatic interaction promotes energetically favorable mutual orientation of protein molecules at distances between their cofactors shorter than 5 nm. At distances shorter than 3 nm, these electrostatic interactions lead to a significantly detectable increase in the rate of convergence of the cofactors.
May 2016: Doklady. Biochemistry and Biophysics
N E Belyaeva, A A Bulychev, G Yu Riznichenko, A B Rubin
A new Thylakoid model is presented, which describes in detail the electron/proton transfer reactions between membrane protein complexes including photosystems II and I (PSII, PSI), cytochrome (Cyt) b 6 f, mobile plastoquinone PQ pool in the thylakoid membrane, plastocyanin in lumen and ferredoxin in stroma, reduction of NADP via FNR and cyclic electron transfer. The Thylakoid model parameters were fitted both to Chl fluorescence induction data (FI) and oxido-reductions of P700 (ΔA 810) measured from 20 μs up to 20 s in pea leaves...
July 1, 2016: Photosynthesis Research
George Thomas, Elisa Andresen, Jürgen Mattusch, Tomáš Hubáček, Hendrik Küpper
Essential trace elements (Cu(2+), Zn(2+), etc) lead to toxic effects above a certain threshold, which is a major environmental problem in many areas of the world. Here, environmentally relevant sub-micromolar concentrations of Cu(2+) and simulations of natural light and temperature cycles were applied to the aquatic macrophyte Ceratophyllum demersum a s a model for plant shoots. In this low irradiance study resembling non-summer conditions, growth was optimal in the range 7.5-35nM Cu, while PSII activity (Fv/Fm) was maximal around 7...
August 2016: Aquatic Toxicology
Amanda L Le Sueur, Richard N Schaugaard, Mu-Hyun Baik, Megan C Thielges
The reactivity of metal sites in proteins is tuned by protein-based ligands. For example, in blue copper proteins such as plastocyanin (Pc), the structure imparts a highly elongated bond between the Cu and a methionine (Met) axial ligand to modulate its redox properties. Despite extensive study, a complete understanding of the contribution of the protein to redox activity is challenged by experimentally accessing both redox states of metalloproteins. Using infrared (IR) spectroscopy in combination with site-selective labeling with carbon-deuterium (C-D) vibrational probes, we characterized the localized changes at the Cu ligand Met97 in the oxidized and reduced states, as well as the Zn(II) or Co(II)-substituted, the pH-induced low-coordinate, the apoprotein, and the unfolded states...
June 8, 2016: Journal of the American Chemical Society
Richard Malkin
David Knaff began his scientific career in the Department of Cell Physiology at the University of California, Berkeley. At Berkeley, he worked on chloroplast electron carriers such as the cytochromes and plastocyanin and applied redox potentiometry to characterize these carriers in situ. He moved to Texas Tech University where he made major contributions in the study of ferredoxin-mediated reactions with chloroplast enzymes, most notably nitrite reductase.
July 2016: Photosynthesis Research
Agu Laisk, Vello Oja, Hillar Eichelmann
Electrochromic shift measurements confirmed that the Q-cycle operated in sunflower leaves. The slow temporarily increasing post-pulse phase was recorded, when ATP synthase was inactivated in the dark and plastoquinol (PQH(2)) oxidation was initiated by a short pulse of far-red light (FRL). During illumination by red light, the Q-cycle-supported proton arrival at the lumen and departure via ATP synthase were simultaneous, precluding extreme build-up of the membrane potential. To investigate the kinetics of the Q-cycle, less than one PQH(2) per cytochrome b(6)f (Cyt b(6)f) were reduced by illuminating the leaf with strong light pulses or single-turnover Xe flashes...
June 2016: Biochimica et Biophysica Acta
Ulrich Schreiber, Christof Klughammer
The newly developed Dual/KLAS-NIR spectrophotometer, technical details of which were reported very recently, is used in measuring redox changes of P700, plastocyanin (PC) and ferredoxin (Fd) in intact leaves ofHedera helix,Taxus baccataandBrassica napus An overview of various light-/dark-induced changes of deconvoluted P700(+), PC(+)and Fd(-)signals is presented demonstrating the wealth of novel information and the consistency of the obtained results. Fd(-)changes are particularly large after dark adaptation...
April 5, 2016: Plant & Cell Physiology
Christof Klughammer, Ulrich Schreiber
A newly developed compact measuring system for assessment of transmittance changes in the near-infrared spectral region is described; it allows deconvolution of redox changes due to ferredoxin (Fd), P700, and plastocyanin (PC) in intact leaves. In addition, it can also simultaneously measure chlorophyll fluorescence. The major opto-electronic components as well as the principles of data acquisition and signal deconvolution are outlined. Four original pulse-modulated dual-wavelength difference signals are measured (785-840 nm, 810-870 nm, 870-970 nm, and 795-970 nm)...
May 2016: Photosynthesis Research
Haiyun Jin, Puja Goyal, Akshaya Kumar Das, Michael Gaus, Markus Meuwly, Qiang Cui
We apply two recently developed computational methods, DFTB3 and VALBOND, to study copper oxidation/reduction processes in solution and protein. The properties of interest include the coordination structure of copper in different oxidation states in water or in a protein (plastocyanin) active site, the reduction potential of the copper ion in different environments, and the environmental response to copper oxidation. The DFTB3/MM and VALBOND simulation results are compared to DFT/MM simulations and experimental results whenever possible...
March 3, 2016: Journal of Physical Chemistry. B
Elisabetta Salvatori, Lina Fusaro, Reto J Strasser, Filippo Bussotti, Fausto Manes
The response of PSII and PSI photochemistry to acute ozone (O3) stress was tested in a "model plant system", namely the O3 sensitive (S156) and O3 resistant (R123) genotype pairs of Phaseolus vulgaris L., during a phenological phase of higher O3 sensitivity (pod formation). The modulation of the photosynthetic activity during O3 stress was analysed by measuring gas exchanges, Prompt Fluorescence (PF, JIP-test) and 820 nm Modulated Reflectance (MR), a novel techniques which specifically detects the changes in the redox state of P700 and plastocyanin...
December 2015: Plant Physiology and Biochemistry: PPB
A Yu Semenov, A A Petrova, M D Mamedov, V A Nadtochenko
The pigment-protein complex of photosystem I (PS I) catalyzes light-driven oxidation of plastocyanin or cytochrome c6 and reduction of ferredoxin or flavodoxin in oxygenic photosynthetic organisms. In this review, we describe the current state of knowledge of the processes of excitation energy transfer and formation of the primary and secondary ion-radical pairs within PS I. The electron transfer reaction involving quinone cofactor in the A1 site and its role in providing asymmetry of electron transport as well as interaction with oxygen and ascorbate in PS I are discussed...
June 2015: Biochemistry. Biokhimii︠a︡
Pilar Bernal-Bayard, Chiara Pallara, M Carmen Castell, Fernando P Molina-Heredia, Juan Fernández-Recio, Manuel Hervás, José A Navarro
In the Phaeodactylum tricornutum alga, as in most diatoms, cytochrome c6 is the only electron donor to photosystem I, and thus they lack plastocyanin as an alternative electron carrier. We have investigated, by using laser-flash absorption spectroscopy, the electron transfer to Phaeodactylum photosystem I from plastocyanins from cyanobacteria, green algae and plants, as compared with its own cytochrome c6. Diatom photosystem I is able to effectively react with eukaryotic acidic plastocyanins, although with less efficiency than with Phaeodactylum cytochrome c6...
December 2015: Biochimica et Biophysica Acta
Giada Cattani, Lutz Vogeley, Peter B Crowley
PEGylated proteins are a mainstay of the biopharmaceutical industry. Although the use of poly(ethylene glycol) (PEG) to increase particle size, stability and solubility is well-established, questions remain as to the structure of PEG-protein conjugates. Here we report the structural characterization of a model β-sheet protein (plastocyanin, 11.5 kDa) modified with a single PEG 5,000. An NMR spectroscopy study of the PEGylated conjugate indicated that the protein and PEG behaved as independent domains. A crystal structure revealed an extraordinary double-helical assembly of the conjugate, with the helices arranged orthogonally to yield a highly porous architecture...
October 2015: Nature Chemistry
Jefferson S Plegaria, Matteo Duca, Cédric Tard, Thomas J Friedlander, Aniruddha Deb, James E Penner-Hahn, Vincent L Pecoraro
Using de novo protein design, we incorporated a copper metal binding site within the three-helix bundle α3D (Walsh et al. Proc. Natl. Acad. Sci. U.S.A. 1999, 96, 5486-5491) to assess whether a cupredoxin center within an α-helical domain could mimic the spectroscopic, structural, and redox features of native type-1 copper (CuT1) proteins. We aimed to determine whether a CuT1 center could be realized in a markedly different scaffold rather than the native β-barrel fold and whether the characteristic short Cu-S bond (2...
October 5, 2015: Inorganic Chemistry
Wiebke Tapken, Karl Ravet, Muhammad Shahbaz, Marinus Pilon
Plastocyanin is a copper (Cu)-requiring protein that functions in photosynthetic electron transport in the thylakoid lumen of plants. To allow plastocyanin maturation, Cu must first be transported into the chloroplast stroma by means of the PAA1/HMA6 transporter and then into the thylakoid lumen by the PAA2/HMA8 transporter. Recent evidence indicated that the chloroplast regulates Cu transport into the thylakoids via Clp protease-mediated turnover of PAA2/HMA8. Here we present further genetic evidence that this regulatory mechanism for the adjustment of intra-cellular Cu distribution depends on stromal Cu levels...
2015: Plant Signaling & Behavior
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