Probing the Functional Role of Ca2+in the Oxygen-Evolving Complex of Photosystem II by Metal Ion Inhibition†

Biochemistry ◽  
2007 ◽  
Vol 46 (11) ◽  
pp. 3211-3223 ◽  
Author(s):  
Cheng-I Lee ◽  
K. V. Lakshmi ◽  
Gary W. Brudvig
Keyword(s):  
Photosystem Ii ◽  
Metal Ion ◽  
Functional Role ◽  
Oxygen Evolving Complex ◽  
Oxygen Evolving

Role of Phosphatidylglycerol in Oxygen-Evolving Complex of Photosystem II

2008 ◽  
pp. 463-466 ◽  
Author(s):  
Naoki Mizusawa ◽  
Isamu Sakurai ◽  
Hisako Kubota ◽  
Hajime Wada
Keyword(s):  
Photosystem Ii ◽  
Oxygen Evolving Complex ◽  
Oxygen Evolving

Electron donation to photosystem II by diphenylcarbazide is inhibited both by the endogenous manganese complex and by exogenous manganese ions

1995 ◽  
Vol 73 (5-6) ◽  
pp. 241-245 ◽  
Author(s):  
Abdur Rashid ◽  
Radovan Popovic
Keyword(s):  
Photosystem Ii ◽  
Antagonistic Effect ◽  
Oxygen Evolving Complex ◽  
Manganese Ions ◽  
Extrinsic Polypeptides ◽  
Negative Role ◽  
Mn Cluster ◽  
Oxygen Evolving ◽  
Electron Donation

Diphenylcarbazide (DPC) is an efficient electron donor to the inactive oxygen-evolving complex of photosystem II (PSII). We investigated the role of manganese on the rate of electron donation from DPC to PSII in both Mn-depleted (Tris washed) and Mn-retaining (NaCl washed) PSII preparations. The rate of electron donation from DPC to PSII was significantly higher in Mn-depleted than in Mn-retaining preparations, indicating a negative role of native Mn complex on DPC electron donation. The apparent Km values for DPC were found to be 0.11 and 0.17 mM for Mn-depleted and Mn-retaining PSII preparations, respectively. This difference in the Km values also indicates an antagonistic effect of endogenous Mn cluster on electron donation from DPC, which was markedly inhibited by exogenous Mn2+. However, the magnitude of inhibition was greater in Mn-depleted than in Mn-retaining PSII preparations. This indicates a higher accessibility of DPC to PSII in the absence of native Mn complex. Our results suggest (i) that Mn, either endogenous or added, acts as an accessibility barrier for DPC to donate electrons to PSII and (ii) that the native Mn complex not only functions as an accumulator of oxidizing equivalents but may also protect PSII from exogenous reductants.Key words: photosystem II, extrinsic polypeptides, Mn complex, electron transport, diphenylcarbazide.

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.

scholarly journals Role of redox-inactive metals in controlling the redox potential of heterometallic manganese–oxido clusters

2021 ◽  
Author(s):  
Keisuke Saito ◽  
Minesato Nakagawa ◽  
Manoj Mandal ◽  
Hiroshi Ishikita
Keyword(s):  
Photosystem Ii ◽  
Redox Potential ◽  
Quantum Chemical Calculations ◽  
Catalytic Reaction ◽  
Quantum Chemical ◽  
Ionic Radius ◽  
Redox Potentials ◽  
Oxygen Evolving ◽  
Highest Occupied Molecular Orbitals

AbstractPhotosystem II (PSII) contains Ca2+, which is essential to the oxygen-evolving activity of the catalytic Mn4CaO5 complex. Replacement of Ca2+ with other redox-inactive metals results in a loss/decrease of oxygen-evolving activity. To investigate the role of Ca2+ in this catalytic reaction, we investigate artificial Mn3[M]O2 clusters redox-inactive metals  [M] ([M]  = Mg2+, Ca2+, Zn2+, Sr2+, and Y3+), which were synthesized by Tsui et al. (Nat Chem 5:293, 2013). The experimentally measured redox potentials (Em) of these clusters are best described by the energy of their highest occupied molecular orbitals. Quantum chemical calculations showed that the valence of metals predominantly affects Em(MnIII/IV), whereas the ionic radius of metals affects Em(MnIII/IV) only slightly.

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