scholarly journals Photosystem II does not convert nascent oxygen to the poisonous singlet form

2019 ◽  
Author(s):  
Heta Mattila ◽  
Esa Tyystjärvi
Keyword(s):  
Photosystem Ii ◽  
Oxidative Damage ◽  
Triplet State ◽  
Singlet Oxygen ◽  
Water Splitting ◽  
Oxygenic Photosynthesis ◽  
Primary Donor ◽  
Independent Mechanism ◽  
Per Se

AbstractIn the light, the Mn4CaO5 complex of Photosystem II (PSII) splits water producing O2 and the triplet state of the primary donor (3P680) of PSII generates reactive singlet oxygen (1O2). We show that nascent O2 is not converted to 1O2, but originates exclusively from ambient O2, indicating that the sensitivity of PSII to oxidative damage is not a consequence of the water-splitting per se, and showing that the suggested oxygen channels function nearly perfectly, conveying nascent O2 out of the reach of 3P680. This may have been crucial during evolution of oxygenic photosynthesis, as 3P680 cannot be quenched by carotenoids that protect non- oxygenic photosystems. In addition, the data indicate that a 1O2-independent mechanism contributes to the light-induced damage of PSII.

scholarly journals Mediator-assisted water oxidation by the ruthenium “blue dimer” cis,cis-[(bpy)2(H2O)RuORu(OH2)(bpy)2]4+

2008 ◽  
Vol 105 (46) ◽  
pp. 17632-17635 ◽  
Author(s):  
Javier J. Concepcion ◽  
Jonah W. Jurss ◽  
Joseph L. Templeton ◽  
Thomas J. Meyer
Keyword(s):  
Carbon Dioxide ◽  
Electron Transfer ◽  
Renewable Energy ◽  
Photosystem Ii ◽  
Water Splitting ◽  
Water Oxidation ◽  
Oxygenic Photosynthesis ◽  
Reduced Water ◽  
Insight Into ◽  
Recent Insight

Light-driven water oxidation occurs in oxygenic photosynthesis in photosystem II and provides redox equivalents directed to photosystem I, in which carbon dioxide is reduced. Water oxidation is also essential in artificial photosynthesis and solar fuel-forming reactions, such as water splitting into hydrogen and oxygen (2 H2O + 4 hν → O2 + 2 H2) or water reduction of CO2 to methanol (2 H2O + CO2 + 6 hν → CH3OH + 3/2 O2), or hydrocarbons, which could provide clean, renewable energy. The “blue ruthenium dimer,” cis,cis-[(bpy)2(H2O)RuIIIORuIII(OH2)(bpy)2]4+, was the first well characterized molecule to catalyze water oxidation. On the basis of recent insight into the mechanism, we have devised a strategy for enhancing catalytic rates by using kinetically facile electron-transfer mediators. Rate enhancements by factors of up to ≈30 have been obtained, and preliminary electrochemical experiments have demonstrated that mediator-assisted electrocatalytic water oxidation is also attainable.

scholarly journals Exploring the Link between Photosystem II Assembly and Translation of the Chloroplast psbA mRNA

Plants ◽  
2020 ◽  
Vol 9 (2) ◽  
pp. 152 ◽  
Author(s):  
Prakitchai Chotewutmontri ◽  
Rosalind Williams-Carrier ◽  
Alice Barkan
Keyword(s):  
Photosystem Ii ◽  
Water Splitting ◽  
Reaction Center ◽  
Ribosome Profiling ◽  
Oxygenic Photosynthesis ◽  
Dual Roles ◽  
Psii Reaction Center ◽  
Core Proteins ◽  
Prosthetic Groups ◽  
Autoregulatory Mechanism

Photosystem II (PSII) in chloroplasts and cyanobacteria contains approximately fifteen core proteins, which organize numerous pigments and prosthetic groups that mediate the light-driven water-splitting activity that drives oxygenic photosynthesis. The PSII reaction center protein D1 is subject to photodamage, whose repair requires degradation of damaged D1 and its replacement with nascent D1. Mechanisms that couple D1 synthesis with PSII assembly and repair are poorly understood. We address this question by using ribosome profiling to analyze the translation of chloroplast mRNAs in maize and Arabidopsis mutants with defects in PSII assembly. We found that OHP1, OHP2, and HCF244, which comprise a recently elucidated complex involved in PSII assembly and repair, are each required for the recruitment of ribosomes to psbA mRNA, which encodes D1. By contrast, HCF136, which acts upstream of the OHP1/OHP2/HCF244 complex during PSII assembly, does not have this effect. The fact that the OHP1/OHP2/HCF244 complex brings D1 into proximity with three proteins with dual roles in PSII assembly and psbA ribosome recruitment suggests that this complex is the hub of a translational autoregulatory mechanism that coordinates D1 synthesis with need for nascent D1 during PSII biogenesis and repair.

scholarly journals What is β–carotene doing in the photosystem II reaction centre?

2002 ◽  
Vol 357 (1426) ◽  
pp. 1431-1440 ◽  
Author(s):  
Alison Telfer
Keyword(s):  
Electron Transfer ◽  
Photosystem Ii ◽  
Excitation Energy ◽  
Triplet State ◽  
Singlet Oxygen ◽  
Spin Exchange ◽  
Primary Electron ◽  
Triplet States ◽  
Reaction Centre ◽  
Β Carotene

During photosynthesis carotenoids normally serve as antenna pigments, transferring singlet excitation energy to chlorophyll, and preventing singlet oxygen production from chlorophyll triplet states, by rapid spin exchange and decay of the carotenoid triplet to the ground state. The presence of two β–carotene molecules in the photosystem II reaction centre (RC) now seems well established, but they do not quench the triplet state of the primary electron–donor chlorophylls, which are known as P 680 . The β–carotenes cannot be close enough to P 680 for triplet quenching because that would also allow extremely fast electron transfer from β–carotene to P + 680 , preventing the oxidation of water. Their transfer of excitation energy to chlorophyll, though not very efficient, indicates close proximity to the chlorophylls ligated by histidine 118 towards the periphery of the two main RC polypeptides. The primary function of the β–carotenes is probably the quenching of singlet oxygen produced after charge recombination to the triplet state of P 680 . Only when electron donation from water is disturbed does β–carotene become oxidized. One β–carotene can mediate cyclic electron transfer via cytochrome b 559. The other is probably destroyed upon oxidation, which might trigger a breakdown of the polypeptide that binds the cofactors that carry out charge separation.

scholarly journals Photosystem II assembly factor HCF136 from A. thaliana at 1.67 Å resolution

2014 ◽  
Vol 70 (a1) ◽  
pp. C1170-C1170
Author(s):  
Roland Bergdahl ◽  
Christin Grundström ◽  
Patrik Storm ◽  
Wolfgang Schröder ◽  
Uwe Sauer
Keyword(s):  
Photosystem Ii ◽  
Water Splitting ◽  
D1 Protein ◽  
Oxygenic Photosynthesis ◽  
Reaction Centre ◽  
Cytochrome B559 ◽  
Irreversible Damage ◽  
Redox Active ◽  
Assembly Factor ◽  
High Level

The High Chlorophyll Fluorescence 136 protein (HCF136) is essential for the assembly and repair of Photosystem II (PSII) and its central reaction centre (RC)[1]. HCF136 is an abundant protein in the thylakoid lumen and has been suggested to directly interact with subunits of the RC. The multi-subunit pigment-protein PSII complex is imbedded in the thylakoid membrane of the oxygenic photosynthetic organisms, and responsible for water splitting during oxygenic photosynthesis. PSII harbours more than 20 different integral and peripheral membrane proteins and its assembly requires a high level of coordination[2]. Two proteins D1 (psbA) and D2 (psbD) form the core of the complex and bind most of the redox-active co-factors. The PSII RC contains, in addition to D1 and D2, the intrinsic PsbI subunit and cytochrome b559. Light is a harmful substrate and subunits are damaged during the water-splitting reaction. The largest irreversible damage is experienced by the central D1 protein that has the highest turnover rate of all thylakoid proteins. Analysis of mutated A. thaliana has identified HCF136 as an essential factor for PSII RC assembly and RC turnover and repair[3]. In order to gain functional and structural insight in the way the HCF136 protein is involved in the PSII repair cycle, we have cloned, expressed, purified and crystallized the HCF136 protein from A. thaliana. Here we present the structure of this doughnut shaped WD40 domain family protein determined at 1.67 Å resolution. Biochemical and biophysical analysis of HCF136 and components of the PSII RC are under way.

scholarly journals Singlet oxygen damages the function of Photosystem II in isolated thylakoids and in the green alga Chlorella sorokiniana

2021 ◽  
Author(s):  
Faiza Bashir ◽  
Ateeq Ur Rehman ◽  
Milán Szabó ◽  
Imre Vass
Keyword(s):  
Photosystem Ii ◽  
Singlet Oxygen ◽  
Screening Method ◽  
Physiological Role ◽  
Thylakoid Membranes ◽  
Chlorella Sorokiniana ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Intact Cells ◽  
Green Alga Chlorella

AbstractSinglet oxygen (1O2) is an important damaging agent, which is produced during illumination by the interaction of the triplet excited state pigment molecules with molecular oxygen. In cells of photosynthetic organisms 1O2 is formed primarily in chlorophyll containing complexes, and damages pigments, lipids, proteins and other cellular constituents in their environment. A useful approach to study the physiological role of 1O2 is the utilization of external photosensitizers. In the present study, we employed a multiwell plate-based screening method in combination with chlorophyll fluorescence imaging to characterize the effect of externally produced 1O2 on the photosynthetic activity of isolated thylakoid membranes and intact Chlorella sorokiniana cells. The results show that the external 1O2 produced by the photosensitization reactions of Rose Bengal damages Photosystem II both in isolated thylakoid membranes and in intact cells in a concentration dependent manner indicating that 1O2 plays a significant role in photodamage of Photosystem II.

[18O]-Labeled Singlet Oxygen as a Tool for Mechanistic Studies of 8-Oxo-7,8-Dihydroguanine Oxidative Damage: Detection of Spiroiminodihydantoin, Imidazolone and Oxazolone Derivatives

2002 ◽  
Vol 383 (3-4) ◽  
Author(s):  
G.R. Martinez ◽  
M.H.G. Medeiros ◽  
J.-L. Ravanat ◽  
J. Cadet ◽  
P. Di Mascio
Keyword(s):  
Oxidative Damage ◽  
Damage Detection ◽  
Singlet Oxygen ◽  
Mechanistic Studies
Sign in / Sign up

Export Citation Format

Share Document