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

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

10.20944/preprints201906.0278.v1 ◽

2019 ◽

Author(s):

Faisal Hammad Mekky 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

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

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Ammonia-Induced Structural Changes of the Oxygen-Evolving Complex in Photosystem II Diminished at 277 K as Revealed by Light-Induced FTIR Difference Spectroscopy

Photosynthesis. Energy from the Sun ◽

10.1007/978-1-4020-6709-9_87 ◽

2008 ◽

pp. 389-391

Author(s):

Hsin-Ho Huang ◽

Tung-Hei Wang ◽

Hsiu-An Chu

Keyword(s):

Photosystem Ii ◽

Structural Changes ◽

Oxygen Evolving Complex ◽

Difference Spectroscopy ◽

Ftir Difference Spectroscopy ◽

Oxygen Evolving

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Simulation of the isotropic EXAFS spectra for the S2 and S3 structures of the oxygen evolving complex in photosystem II

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1422058112 ◽

2015 ◽

Vol 112 (13) ◽

pp. 3979-3984 ◽

Cited By ~ 26

Author(s):

Xichen Li ◽

Per E. M. Siegbahn ◽

Ulf Ryde

Keyword(s):

Photosystem Ii ◽

Water Oxidation ◽

Density Functional ◽

Structural Changes ◽

Complete Agreement ◽

Oxygen Evolving Complex ◽

Chemical Modeling ◽

Oxygen Evolving ◽

High Degree ◽

Exafs Spectra

Most of the main features of water oxidation in photosystem II are now well understood, including the mechanism for O–O bond formation. For the intermediate S2 and S3 structures there is also nearly complete agreement between quantum chemical modeling and experiments. Given the present high degree of consensus for these structures, it is of high interest to go back to previous suggestions concerning what happens in the S2–S3 transition. Analyses of extended X-ray adsorption fine structure (EXAFS) experiments have indicated relatively large structural changes in this transition, with changes of distances sometimes larger than 0.3 Å and a change of topology. In contrast, our previous density functional theory (DFT)(B3LYP) calculations on a cluster model showed very small changes, less than 0.1 Å. It is here found that the DFT structures are also consistent with the EXAFS spectra for the S2 and S3 states within normal errors of DFT. The analysis suggests that there are severe problems in interpreting EXAFS spectra for these complicated systems.

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