scholarly journals Amino acid residues involved in the coordination and assembly of the manganese cluster of photosystem II. Proton-coupled electron transport of the redox-active tyrosines and its relationship to water oxidation

2001 ◽  
Vol 1503 (1-2) ◽  
pp. 147-163 ◽  
Author(s):  
Bruce A Diner
Keyword(s):  
Amino Acid ◽  
Electron Transport ◽  
Photosystem Ii ◽  
Water Oxidation ◽  
Amino Acid Residues ◽  
Manganese Cluster ◽  
Redox Active

Effect of Magnesium and Calcium Ions on the Photoelectron Transport Activity of Low-Salt Suspended Hydrilla verticillata Thylakoids: Possible Sites of Cation Interaction

1998 ◽  
Vol 53 (9-10) ◽  
pp. 849-856
Author(s):  
Sujata R. Mishra ◽  
Surendra Chandra Sabat
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Electron Donor ◽  
Water Oxidation ◽  
Electron Flow ◽  
Hydrilla Verticillata ◽  
Transport Activity ◽  
Low Salt ◽  
Electron Transport Activity ◽  
Stimulation Of

Stimulatory effect of divalent cations like calcium (Ca2+) and magnesium (Mg2+) was investigated on electron transport activity of divalent cation deficient low-salt suspended (LS) thylakoid preparation from a submerged aquatic angiosperm, Hydrilla verticillata. Both the cations stimulated electron transport activity of LS-suspended thylakoids having an intact water oxidation complex. But in hydroxylamine (NH2OH) - or alkaline Tris - washed thylakoid preparations (with the water oxidation enzyme impaired), only Ca2+ dependent stimulation of electron transport activity was found. The apparent Km of Ca2+ dependent stimulation of electron flow from H2O (endogenous) or from artificial electron donor (exogenous) to dichlorophenol indophenol (acceptor) was found to be identical. Calcium supported stimulation of electron transport activity in NH2OH - or Tris - washed thylakoids was electron donor selective, i.e., Ca2+ ion was only effective in electron flow with diphenylcarbazide but not with NH2OH as electron donor to photosystem II. A magnesium effect was observed in thylakoids having an intact water oxidation complex and the ion became unacceptable in NH2OH - or Tris - washed thylakoids. Indirect experimental evidences have been presented to suggest that Mg2+ interacts with the water oxidation complex, while the Ca2+ interaction is localized betw een Yz and reaction center of photosystem II.

scholarly journals Electron, proton and hydrogen–atom transfers in photosynthetic water oxidation

2002 ◽  
Vol 357 (1426) ◽  
pp. 1383-1394 ◽  
Author(s):  
Cecilia Tommos
Keyword(s):  
Photosystem Ii ◽  
Proton Transfer ◽  
Water Oxidation ◽  
Oxidation Mechanism ◽  
Bulk Solution ◽  
Hydrogen Atoms ◽  
Redox Active ◽  
Hydrogen Atom Transfers ◽  
Reduce Carbon Dioxide ◽  
Photosynthetic Water Oxidation

When photosynthetic organisms developed so that they could use water as an electron source to reduce carbon dioxide, the stage was set for efficient proliferation. Algae and plants spread globally and provided the foundation for our atmosphere and for O 2 –based chemistry in biological systems. Light–driven water oxidation is catalysed by photosystem II, the active site of which contains a redox–active tyrosine denoted Y Z , a tetramanganese cluster, calcium and chloride. In 1995, Gerald Babcock and co–workers presented the hypothesis that photosynthetic water oxidation occurs as a metallo–radical catalysed process. In this model, the oxidized tyrosine radical is generated by coupled proton/electron transfer and re–reduced by abstracting hydrogen atoms from substrate water or hydroxide–ligated to the manganese cluster. The proposed function of Y Z requires proton transfer from the tyrosine site upon oxidation. The oxidation mechanism of Y Z in an inhibited and O 2 –evolving photosystem II is discussed. Domino–deprotonation from Y Z to the bulk solution is shown to be consistent with a variety of data obtained on metal–depleted samples. Experimental data that suggest that the oxidation of Y Z in O 2 –evolving samples is coupled to proton transfer in a hydrogen–bonding network are described. Finally, a dielectric–dependent model for the proton release that is associated with the catalytic cycle of photosystem II is discussed.

Structure - function analysis of photosystem II subunit S (PsbS) in vivo

2002 ◽  
Vol 29 (10) ◽  
pp. 1131 ◽  
Author(s):  
Xiao-Ping Li ◽  
Alba Phippard ◽  
Jae Pasari ◽  
Krishna K. Niyogi
Keyword(s):  
Amino Acid ◽  
Photosystem Ii ◽  
Function Analysis ◽  
Amino Acid Sequences ◽  
Forward Genetics ◽  
Photochemical Quenching ◽  
Amino Acid Residues ◽  
The Stability ◽  
Psbs Gene

In land plants, photosystem II subunit S (PsbS) plays a key role in xanthophyll- and pH-dependent non-photochemical quenching (qE) of excess absorbed light energy. Arabidopsis thaliana (L.) Heynh. npq4 mutants are defective in the psbS gene and have impaired qE. Exactly how the PsbS protein is involved in qE is unclear, but it has been proposed that PsbS binds H+ and/or de-epoxidized xanthophylls in excess light as part of the qE mechanism. To identify amino acid residues that are important for PsbS function, we sequenced the psbS gene from eight npq4 point mutant alleles isolated by forward genetics screening, including two new alleles. In the four transmembrane helices of PsbS, several amino acid residues were found to affect the stability and/or function of the protein. By comparing the predicted amino acid sequences of PsbS from several plant species and studying the proposed topological structure of PsbS, eight possible H+-binding amino acid residues on the lumenal side of the protein were identified and then altered by site-directed mutagenesis in vitro. The mutant psbS genes were transformed into npq4-1, a psbS deletion mutant, to test the stability and function of the mutant PsbS proteins in�vivo. The results demonstrate that two conserved, protonatable amino acids, E122 and E226, are especially critical for the function of PsbS.

Site-directed mutagenesis of amino acid residues of D1 protein interacting with phosphatidylglycerol affects the function of plastoquinone QB in photosystem II

2015 ◽  
Vol 126 (2-3) ◽  
pp. 385-397 ◽  
Author(s):  
Kaichiro Endo ◽  
Naoki Mizusawa ◽  
Jian-Ren Shen ◽  
Masato Yamada ◽  
Tatsuya Tomo ◽  
...  
Keyword(s):  
Amino Acid ◽  
Photosystem Ii ◽  
D1 Protein ◽  
Site Directed Mutagenesis ◽  
Directed Mutagenesis ◽  
Amino Acid Residues

Pivotal role of the redox-active tyrosine in driving the water splitting catalyzed by photosystem II

2020 ◽  
Vol 22 (1) ◽  
pp. 273-285 ◽  
Author(s):  
Shin Nakamura ◽  
Matteo Capone ◽  
Daniele Narzi ◽  
Leonardo Guidoni
Keyword(s):  
Hydrogen Bond ◽  
Photosystem Ii ◽  
Water Splitting ◽  
Oxidation State ◽  
Water Oxidation ◽  
Oxidation Catalysis ◽  
Pivotal Role ◽  
Redox Active ◽  
Water Oxidation Catalysis

TyrZ oxidation state triggers hydrogen bond modification in the water oxidation catalysis.

Isolation and Partial Characterization of a Manganese Requiring ʟ-Arginine Metabolizing Enzyme Being Present in Photosystem II Complexes of Spinach and Tobacco

1995 ◽  
Vol 50 (9-10) ◽  
pp. 638-651 ◽  
Author(s):  
Achim E. Gau ◽  
Hubert H. Thole ◽  
Elfriede K. Pistorius
Keyword(s):  
Photosystem Ii ◽  
Water Oxidation ◽  
Cation Binding ◽  
Active Group ◽  
Anion Exchange Column ◽  
Ps Ii ◽  
Cation Binding Site ◽  
Redox Active ◽  
Metabolizing Enzyme ◽  
Ph Range

Abstract A low ʟ-arginine metabolizing enzyme (L-AME) activity leading to ornithine, urea and additional products not identified so far could be detected in photosystem II (PS II) membranes of spinach and of the chlorophyll deficient tobacco mutant Su/su. The detectable L-AME activity was very low in untreated PS II membranes, but increased significantly (about 10 fold) when the extrinsic peptides (psbO, P and Q gene products) were removed - suggesting that the L-AME is exposed at the lumen side of PS II. It was possible to isolate the detergent-solubilized protein from CaCl2-washed PS II membranes of spinach by a combination of anion and cation exchange columns. On the basis of SDS PAGE the protein was homogenous and had an apparent molecular mass of 7 kDa. N-terminal sequencing of the polypeptide gave a contiguous sequence of 20 amino acids showing no homologies to PS II polypeptides as yet sequenced. After chromatography of the L-AME on an anion exchange column at pH 9.5 (last purification step) a completely inactive enzyme was obtained. Maximal reactivation was achieved by dialyzing the protein against Hepes-NaOH buffer in the pH range of 6.5 to 7.5 containing 100 mᴍ chloride or sulfate (being the most effective anions). The L-AME activity was totally dependent on manganese added to the reaction mixture. Moreover, there were indications of a second cation binding site being more sequestered and requiring bound Ca2+ or Mn2+ for activity (Sr2+ was less effective and Mg2+ was ineffective). There are indications that the protein contains a redox active group - possibly an aminoacid- derived quinonoid (based on a redox cycling assay with glycine and nitroblue tetrazolium). The capability of this PS II associated protein to bind the cofactors of water oxidation and having a redox active group (preliminary results) suggests that this protein might be functional in photosynthetic water oxidation. This is further supported by the fact that the isolated L-AME has a low catalase activity

scholarly journals Water oxidation chemistry of photosystem II

2002 ◽  
Vol 357 (1426) ◽  
pp. 1395-1405 ◽  
Author(s):  
John S. Vrettos ◽  
Gary W. Brudvig
Keyword(s):  
Photosystem Ii ◽  
Water Oxidation ◽  
Ion Selectivity ◽  
Bound Water ◽  
Nucleophilic Attack ◽  
Manganese Cluster ◽  
Bond Forming ◽  
Proton Coupled Electron Transfer ◽  
Tyrosine Z ◽  
Oxidation Chemistry

The O 2 –evolving complex of photosystem II catalyses the light–driven four–electron oxidation of water to dioxygen in photosynthesis. In this article, the steps leading to photosynthetic O 2 evolution are discussed. Emphasis is given to the proton–coupled electron–transfer steps involved in oxidation of the manganese cluster by oxidized tyrosine Z (Y Z ), the function of Ca 2+ and the mechanism by which water is activated for formation of an O–O bond. Based on a consideration of the biophysical studies of photosystem II and inorganic manganese model chemistry, a mechanism for photosynthetic O 2 evolution is presented in which the O–O bond–forming step occurs via nucleophilic attack on an electron–deficient Mn V =O species by a calcium–bound water molecule. The proposed mechanism includes specific roles for the tetranuclear manganese cluster, calcium, chloride, Y Z and His190 of the D1 polypeptide. Recent studies of the ion selectivity of the calcium site in the O 2 –evolving complex and of a functional inorganic manganese model system that test key aspects of this mechanism are also discussed.

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