Structural Dynamics of the Oxygen-Evolving Complex of Photosystem II in Water-Splitting Action

2018 ◽  
Vol 140 (17) ◽  
pp. 5853-5859 ◽  
Author(s):  
Andrew J. Wilson ◽  
Prashant K. Jain
Keyword(s):  
Photosystem Ii ◽  
Water Splitting ◽  
Structural Dynamics ◽  
Oxygen Evolving Complex ◽  
Oxygen Evolving

scholarly journals Metal oxidation states in biological water splitting

2015 ◽  
Vol 6 (3) ◽  
pp. 1676-1695 ◽  
Author(s):  
Vera Krewald ◽  
Marius Retegan ◽  
Nicholas Cox ◽  
Johannes Messinger ◽  
Wolfgang Lubitz ◽  
...  
Keyword(s):  
Photosystem Ii ◽  
Water Splitting ◽  
Oxidation States ◽  
Oxygen Evolving Complex ◽  
Central Question ◽  
Manganese Ions ◽  
Metal Oxidation ◽  
Biological Water ◽  
Oxygen Evolving

A central question in biological water splitting concerns the oxidation states of the manganese ions that comprise the oxygen-evolving complex of photosystem II.

‘Photosystem II: the water splitting enzyme of photosynthesis and the origin of oxygen in our atmosphere’

2016 ◽  
Vol 49 ◽  
Author(s):  
James Barber
Keyword(s):  
Photosystem Ii ◽  
Water Splitting ◽  
Water Oxidation ◽  
18Th Century ◽  
Metal Cluster ◽  
Oxygen Evolving Complex ◽  
Structural Details ◽  
Unlimited Supply ◽  
Lipid Environment ◽  
Oxygen Evolving

AbstractAbout 3 billion years ago an enzyme emerged which would dramatically change the chemical composition of our planet and set in motion an unprecedented explosion in biological activity. This enzyme used solar energy to power the thermodynamically and chemically demanding reaction of water splitting. In so doing it provided biology with an unlimited supply of reducing equivalents needed to convert carbon dioxide into the organic molecules of life while at the same time produced oxygen to transform our planetary atmosphere from an anaerobic to an aerobic state. The enzyme which facilitates this reaction and therefore underpins virtually all life on our planet is known as Photosystem II (PSII). It is a pigment-binding, multisubunit protein complex embedded in the lipid environment of the thylakoid membranes of plants, algae and cyanobacteria. Today we have detailed understanding of the structure and functioning of this key and unique enzyme. The journey to this level of knowledge can be traced back to the discovery of oxygen itself in the 18th-century. Since then there has been a sequence of mile stone discoveries which makes a fascinating story, stretching over 200 years. But it is the last few years that have provided the level of detail necessary to reveal the chemistry of water oxidation and O–O bond formation. In particular, the crystal structure of the isolated PSII enzyme has been reported with ever increasing improvement in resolution. Thus the organisational and structural details of its many subunits and cofactors are now well understood. The water splitting site was revealed as a cluster of four Mn ions and a Ca ion surrounded by amino-acid side chains, of which seven provide direct ligands to the metals. The metal cluster is organised as a cubane structure composed of three Mn ions and a Ca2+ linked by oxo-bonds with the fourth Mn ion attached to the cubane. This structure has now been synthesised in a non-protein environment suggesting that it is a totally inorganic precursor for the evolution of the photosynthetic oxygen-evolving complex. In summary, the overall structure of the catalytic site has given a framework on which to build a mechanistic scheme for photosynthetic dioxygen generation and at the same time provide a blue-print and incentive to develop catalysts for artificial photo-electrochemical systems to split water and generate renewable solar fuels.

scholarly journals Structural Changes in the Acceptor Site of Photosystem II upon Ca2+/Sr2+ Exchange in the Mn4CaO5 Cluster Site and the Possible Long-Range Interactions

Biomolecules ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 371
Author(s):  
Koua
Keyword(s):  
Crystal Structure ◽  
Photosystem Ii ◽  
Long Range ◽  
Electron Acceptor ◽  
Structural Changes ◽  
Acceptor Site ◽  
Oxygen Evolving Complex ◽  
Long Range Interactions ◽  
Structural Perturbations ◽  
Oxygen Evolving

The Mn4CaO5 cluster site in the oxygen-evolving complex (OEC) of photosystem II (PSII) undergoes structural perturbations, such as those induced by Ca2+/Sr2+ exchanges or Ca/Mn removal. These changes have been known to induce long-range positive shifts (between +30 and +150 mV) in the redox potential of the primary quinone electron acceptor plastoquinone A (QA), which is located 40 Å from the OEC. To further investigate these effects, we reanalyzed the crystal structure of Sr-PSII resolved at 2.1 Å and compared it with the native Ca-PSII resolved at 1.9 Å. Here, we focus on the acceptor site and report the possible long-range interactions between the donor, Mn4Ca(Sr)O5 cluster, and acceptor sites.

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