scholarly journals The molecular pH-response mechanism of the plant light-stress sensor PsbS

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Maithili Krishnan-Schmieden ◽  
Patrick E. Konold ◽  
John T. M. Kennis ◽  
Anjali Pandit
Keyword(s):  
Protein Interactions ◽  
Physcomitrella Patens ◽  
Light Stress ◽  
Ph Sensor ◽  
Low Ph ◽  
Molecular Response ◽  
Response Mechanism ◽  
Ph Response ◽  
Excess Light ◽  
Shared Motif

AbstractPlants need to protect themselves from excess light, which causes photo-oxidative damage and lowers the efficiency of photosynthesis. Photosystem II subunit S (PsbS) is a pH sensor protein that plays a crucial role in plant photoprotection by detecting thylakoid lumen acidification in excess light conditions via two lumen-faced glutamates. However, how PsbS is activated under low-pH conditions is unknown. To reveal the molecular response of PsbS to low pH, here we perform an NMR, FTIR and 2DIR spectroscopic analysis of Physcomitrella patens PsbS and of the E176Q mutant in which an active glutamate has been replaced. The PsbS response mechanism at low pH involves the concerted action of repositioning of a short amphipathic helix containing E176 facing the lumen and folding of the luminal loop fragment adjacent to E71 to a 310-helix, providing clear evidence of a conformational pH switch. We propose that this concerted mechanism is a shared motif of proteins of the light-harvesting family that may control thylakoid inter-protein interactions driving photoregulatory responses.

scholarly journals The two active glutamates of the plant stress sensor PsbS contribute non-equivalently to its pH-activated molecular response mechanism

2018 ◽  
Author(s):  
Maithili Krishnan ◽  
Patrick E. Konold ◽  
John T.M. Kennis ◽  
Anjali Pandit
Keyword(s):  
Physcomitrella Patens ◽  
Light Stress ◽  
Plant Stress ◽  
Ph Sensor ◽  
Structural Response ◽  
Molecular Response ◽  
Response Mechanism ◽  
Hydrophobic Membrane ◽  
Structural Mechanism ◽  
Ph Response

ABSTRACTThe membrane protein Photosystem II subunit S (PsbS) is a pH sensor that plays an essential role in signaling light stress in plants to prevent photo oxidation and generation of detrimental reactive species. PsbS detects thylakoid lumen acidification in excess light conditions via two glutamates facing the lumen, however, its molecular mechanism for activation has remained elusive. We performed an infrared and 2-dimensional infrared spectroscopic analysis of wild type Physcomitrella patens PsbS and of mutants in which the active glutamates have been replaced: E71Q, E176Q (the equivalent of E69Q and E173Q in spinach PsbS) and the double mutant E71Q/E176Q. We discovered that E71 exerts allosteric control of PsbS dimerization, while E176 is essential for the secondary structural response to low pH. Based on our results, we propose a molecular pH response mechanism that involves re-positioning of the amphipathic short helix facing the lumen, whereby it moves from the aqueous phase into the hydrophobic membrane phase upon lowering the pH. This structural mechanism may be a shared motif of protein molecular switches of the light-harvesting family and its elucidation could open new routes for crops engineering to improve photosynthetic production of biomass.

scholarly journals β-Catenin is a pH sensor with decreased stability at higher intracellular pH

2018 ◽  
Vol 217 (11) ◽  
pp. 3965-3976 ◽  
Author(s):  
Katharine A. White ◽  
Bree K. Grillo-Hill ◽  
Mario Esquivel ◽  
Jobelle Peralta ◽  
Vivian N. Bui ◽  
...  
Keyword(s):  
Intracellular Ph ◽  
Protein Interactions ◽  
Mammalian Cells ◽  
Ph Sensor ◽  
Adherens Junction ◽  
Protein Protein Interactions ◽  
Adherens Junction Protein ◽  
Junction Protein ◽  
Evolutionarily Conserved ◽  
Ph Dependent

β-Catenin functions as an adherens junction protein for cell–cell adhesion and as a signaling protein. β-catenin function is dependent on its stability, which is regulated by protein–protein interactions that stabilize β-catenin or target it for proteasome-mediated degradation. In this study, we show that β-catenin stability is regulated by intracellular pH (pHi) dynamics, with decreased stability at higher pHi in both mammalian cells and Drosophila melanogaster. β-Catenin degradation requires phosphorylation of N-terminal residues for recognition by the E3 ligase β-TrCP. While β-catenin phosphorylation was pH independent, higher pHi induced increased β-TrCP binding and decreased β-catenin stability. An evolutionarily conserved histidine in β-catenin (found in the β-TrCP DSGIHS destruction motif) is required for pH-dependent binding to β-TrCP. Expressing a cancer-associated H36R–β-catenin mutant in the Drosophila eye was sufficient to induce Wnt signaling and produced pronounced tumors not seen with other oncogenic β-catenin alleles. We identify pHi dynamics as a previously unrecognized regulator of β-catenin stability, functioning in coincidence with phosphorylation.

pH-Response Mechanism of a Redox Reaction between Silver Ions and Hydroquinone

2016 ◽  
Vol 120 (40) ◽  
pp. 23104-23110 ◽  
Author(s):  
Tao Xie ◽  
Chao Jing ◽  
Meng Li ◽  
Wei Ma ◽  
Zhifeng Ding ◽  
...  
Keyword(s):  
Redox Reaction ◽  
Silver Ions ◽  
Response Mechanism ◽  
Ph Response

scholarly journals A SOLID Fe2O3-GRAPHITE COMPOSITE ELECTRODE FOR pH MEASUREMENT

2015 ◽  
Vol 12 (12) ◽  
pp. 44-47
Author(s):  
Suchi Srivastava ◽  
Raja Ram Pradhananga
Keyword(s):  
Electrode Potential ◽  
Composite Electrode ◽  
Low Cost ◽  
Ph Sensor ◽  
Potential Gradient ◽  
Graphite Composite ◽  
Ph Response ◽  
Potentiometric Response ◽  
Unit Change ◽  
Oxidized Graphite

A solid Fe2O3-graphite composite electrode was prepared and investigated for use as a potentiometric pH sensor. The electrode was constructed by mixing iron (III) oxide, oxidized graphite and wax that was put over silver disc onto a polypropylene rod. The response of the electrode was investigated by measuring electrode potential as a function of pH.The effect of composition of the electrode material (Fe2O3 and oxidized graphite ration) on the electrode response was investigated. The electrode with 40% Fe2O3, 30% graphite and 30% wax by mass was found to give the best potentiometric response. This electrode behaves in Nernstian manner with a potentiometric gradient of 56.6±0.4 mV per unit change in pH at 25?C within the working range of pH 2-9.The electrode was also used for the end-point detection in potentiometric acid-base titrations and found to be an excellent electrode for pH-metric titration. The effect of oxidation of electrode on pH response was investigated by dipping electrode in 0.1N KMnO4, 1:1HNO3 and 0.1N Ce4+ solutions for different interval of time. This treatment of the electrode with oxidizing agents increased the standard electrode potential of the electrode however potential gradient per unit change in pH remains unaltered. Low cost, quick response and easy to prepare are the advantages of the iron oxide - graphite composite electrode as a pH sensor. However some metal ions and oxidising agents interfered in the determination of pH using this electrode which is the limitation of using these electrodes.Scientific World, Vol. 12, No. 12, September 2014, page 44-47

Photosynthetic Electron Transport Regulates the Expression of Cytosolic Ascorbate Peroxidase Genes in Arabidopsis during Excess Light Stress

1997 ◽  
Vol 9 (4) ◽  
pp. 627 ◽  
Author(s):  
Stanislaw Karpinski ◽  
Carolina Escobar ◽  
Barbara Karpinska ◽  
Gary Creissen ◽  
Philip M. Mullineaux
Keyword(s):  
Electron Transport ◽  
Ascorbate Peroxidase ◽  
Light Stress ◽  
Photosynthetic Electron Transport ◽  
Cytosolic Ascorbate Peroxidase ◽  
Excess Light

A low pH sensor from an esterified pillar[5]arene

2014 ◽  
Vol 50 (7) ◽  
pp. 852-854 ◽  
Author(s):  
Raghuram Reddy Kothur ◽  
Jessica Hall ◽  
Bhavik Anil Patel ◽  
Chi Leng Leong ◽  
Martyn G. Boutelle ◽  
...  
Keyword(s):  
Ph Sensor ◽  
Low Ph ◽  
Pvc Membrane

An esterified pillar[5]arene, incorporated into a PVC membrane, displays a non-Nernstian response to changes in pH.

An aminoquinoline based biocompatible fluorescent and colourimetric pH sensor designed for cancer cell discrimination

2018 ◽  
Vol 42 (24) ◽  
pp. 19818-19826 ◽  
Author(s):  
Jayanta Mandal ◽  
Pravat Ghorai ◽  
Paula Brandão ◽  
Kunal Pal ◽  
Parimal Karmakar ◽  
...  
Keyword(s):  
Cancer Cells ◽  
Cancer Cell ◽  
Low Cost ◽  
Ph Sensor ◽  
Low Ph ◽  
Cell Permeability ◽  
Ph Range ◽  
Cell Discrimination

A simple, low cost aminoquinoline based pH sensor,HLwas prepared and it works at a low pH range.HLexhibits cell permeability and used as an effective tool for differentiating between normal and cancer cells.

scholarly journals Characterization of the Human Cytomegalovirus gH/gL/UL128-131 Complex That Mediates Entry into Epithelial and Endothelial Cells

2007 ◽  
Vol 82 (1) ◽  
pp. 60-70 ◽  
Author(s):  
Brent J. Ryckman ◽  
Barb L. Rainish ◽  
Marie C. Chase ◽  
Jamie A. Borton ◽  
Jay A. Nelson ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Human Cytomegalovirus ◽  
Protein Interactions ◽  
Low Ph ◽  
Protein Protein Interactions ◽  
Biologically Relevant ◽  
Entry Pathway ◽  
Virion Envelope ◽  
Adenovirus Vectors

ABSTRACT The entry of human cytomegalovirus (HCMV) into biologically relevant epithelial and endothelial cells involves endocytosis followed by low-pH-dependent fusion. This entry pathway is facilitated by the HCMV UL128, UL130, and UL131 proteins, which form one or more complexes with the virion envelope glycoprotein gH/gL. gH/gL/UL128-131 complexes appear to be distinct from the gH/gL/gO complex, which likely facilitates entry into fibroblasts. In order to better understand the assembly and protein-protein interactions of gH/gL/UL128-131 complexes, we generated HCMV mutants lacking UL128-131 proteins and nonreplicating adenovirus vectors expressing gH, gL, UL128, UL130, and UL131. Our results demonstrate that UL128, UL130, and UL131 can each independently assemble onto gH/gL scaffolds. However, the binding of individual UL128-131 proteins onto gH/gL can significantly affect the binding of other proteins; for example, UL128 increased the binding of both UL130 and UL131 to gH/gL. Direct interactions between gH/UL130, UL130/UL131, gL/UL128, and UL128/UL130 were also observed. The export of gH/gL complexes from the endoplasmic reticulum (ER) to the Golgi apparatus and cell surface was dramatically increased when all of UL128, UL130, and UL131 were coexpressed with gH/gL (with or without gO expression). Incorporation of gH/gL complexes into the virion envelope requires transport beyond the ER. Thus, we concluded that UL128, UL130, and UL131 must all bind simultaneously onto gH/gL for the production of complexes that can function in entry into epithelial and endothelial cells.

scholarly journals Role of hydrogen peroxide and the redox state of ascorbate in the induction of antioxidant enzymes in pea leaves under excess light stress

2004 ◽  
Vol 31 (4) ◽  
pp. 359 ◽  
Author(s):  
Jose A. Hernández ◽  
Carolina Escobar ◽  
Gary Creissen ◽  
Phil M. Mullineaux
Keyword(s):  
Antioxidant Enzymes ◽  
Redox State ◽  
Light Stress ◽  
Redox Status ◽  
Protein Accumulation ◽  
Photoinhibition Of Photosynthesis ◽  
Transcript Accumulation ◽  
Land Race ◽  
Excess Light

In this work we used two different pea cultivars, JI281 is a semidomesticated land race of pea from Ethiopia whereas JI399 is a typical domesticated pea variety. Exposure of pea leaves to excess light (EL) for 1 h caused a reversible photoinhibition of photosynthesis as showed by changes in Fv / Fm. Although little difference existed between the two pea genotypes with respect to photoinhibition, after 60 min of EL the decline in Fv / Fm was higher in JI281 than in JI399 leaves. As a consequence of EL, H2O2 increased in both pea cultivars, whereas lipid peroxidation and protein oxidation slightly increased, although differences between cultivars were minimal. The redox state of ascorbate shifted towards its oxidized form under EL stress in both cultivars. Transcript levels of genes coding antioxidant enzymes varied with EL in both cultivars, but the response was more pronounced in JI399. The induction observed during EL was maintained or increased after the stress period, as occurred for cytGR and chlMDHAR. GR protein accumulation and activity correlated with the transcript accumulation in JI399, but not in JI288. In this work, a possible role for H2O2 and redox status of ascorbate in the photoxidative stress signalling is discussed.

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