Stoichiometry of Proton Release from the Catalytic Center in Photosynthetic Water Oxidation

Schlodder, E.; Witt, H. T.

doi:10.1074/jbc.274.43.30387

Cited by 154 publications

(160 citation statements)

References 40 publications

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“…This procedure led to the ligation of about six water and water-derived ligands to the metals of the OEC. Two of these waters, attached respectively to Ca and to Mn(4), were identified as possible substrate water molecules (see below), in agreement with earlier proposals (Haumann & Junge 1999;Hoganson & Babcock 1997;McEvoy & Brudvig 2004;Messinger 2004;Schlodder & Witt 1999), but in contrast to other models suggesting substrate water coordination as oxo-bridges between Mn ions (Brudvig & Crabtree 1986;Nugent et al 2001;Pecoraro et al 1994;Robblee et al 2001;Yachandra et al 1996). The two molecules accounted for the electronic density in the 1S5L XRD structure that was initially assigned to bicarbonate (Ferreira et al 2004).…”

Section: Water Ligationsupporting

confidence: 80%

“…During the S 2 →S 3 transition, the substrate water molecule bound to Mn(4) is deprotonated, consistently with electrochromism data (Haumann & Junge 1996;Junge et al 2002;Lavergne & Junge 1993;Schlodder & Witt 1999;Witt 1996), and the oxidation state of Mn(4) is advanced from III to IV. These changes induce inter-ligand proton transfer from the HO -ligand of Mn (3) to the hydrogen bonded HO -ligand of Mn(4), strengthening the attractive interactions between Mn(4) and the HO -ligand of Mn(3), forming a μ-oxo bridge between Mn(3) and Mn (4), and transforming the HO -ligand of Mn(4) into a water ligand (the HO -proton acceptor is regenerated by deprotonation of the water ligand in the S 0 →S 1 transition).…”

Section: Qm/mm Mechanistic Model Of Water Splittingsupporting

confidence: 74%

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Computational insights into the O2-evolving complex of photosystem II

et al. 2008

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Mechanistic investigations of the water-splitting reaction of the oxygen-evolving complex (OEC) of photosystem II (PSII) are fundamentally informed by structural studies. Many physical techniques have provided important insights into the OEC structure and function, including X-ray diffraction (XRD) and extended X-ray absorption fine structure (EXAFS) spectroscopy as well as mass spectrometry (MS), electron paramagnetic resonance (EPR) spectroscopy and Fourier transform infrared spectroscopy applied in conjunction with mutagenesis studies. However, experimental studies have yet to yield consensus as to the exact configuration of the catalytic metal cluster and its ligation scheme. Computational modeling studies, including density functional (DFT) theory combined with quantum mechanics/molecular mechanics (QM/MM) hybrid methods for explicitly including the influence of the surrounding protein, have proposed chemically satisfactory models of the fully ligated OEC within PSII that are maximally consistent with experimental results. The inorganic core of these models is similar to the crystallographic model upon which they were based but comprises important modifications due to structural refinement, hydration and proteinaceous ligation which improve agreement with a wide range of experimental data. The computational models are useful for rationalizing spectroscopic and crystallographic results and for building a complete structure-based mechanism of water-splitting in PSII as described by the intermediate oxidation states of the OEC. This review summarizes these recent advances in QM/MM modeling of PSII within the context of recent experimental studies.

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Section: Water Ligationsupporting

confidence: 80%

Section: Qm/mm Mechanistic Model Of Water Splittingsupporting

confidence: 74%

Computational insights into the O2-evolving complex of photosystem II

et al. 2008

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“…Probably the structural relaxation reactions take place simultaneously with deprotonation events and O 2 release which can explain the higher transition efficiency than in the S 2 3 S 3 transition. The intermediate transition efficiency in the S 0 3 S 1 transition also can be correlated to the chemistry of this transition (35,50,51) which is considered to involve deprotonation of a -oxo-bridge between two of the manganese atoms (5). This is a smaller structural change than the change in manganese coordination number thought to occur in the S 2 3 S 3 and S 3 3 S 0 transitions.…”

Section: Significance Of Kok Parameters In Our Analysis: Involvement mentioning

confidence: 99%

Misses during Water Oxidation in Photosystem II Are S State-dependent

Han

Mamedov

Styring

2012

Journal of Biological Chemistry

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“…Upon reaching the S 4 state (which may be equivalent to S 3 Y Z ⅐ ) O 2 is released, S 0 is regenerated, and the cycle begins anew. The catalytic site for water oxidation involves an inorganic metal cluster consisting of four manganese ions, one Ca 2ϩ ion, possibly one Cl Ϫ ion, and the redox-active Tyr-161 residue of the D1 reaction center polypeptide (Y Z ) (3)(4)(5)(6). Ligands to the manganese cluster are likely to be derived mostly from the D1 polypeptide, though there are at least 30 other polypeptides involved in the holoenzyme (7,8).…”

mentioning

confidence: 99%

Substrate Water Exchange in Photosystem II Depends on the Peripheral Proteins

Hillier¹,

Hendry²,

Burnap³

et al. 2001

Journal of Biological Chemistry

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The 18 O exchange rates for the substrate water bound in the S 3 state were determined in different photosystem II sample types using time-resolved mass spectrometry. The samples included thylakoid membranes, saltwashed Triton X-100-prepared membrane fragments, and purified core complexes from spinach and cyanobacteria. For each sample type, two kinetically distinct isotopic exchange rates could be resolved, indicating that the biphasic exchange behavior for the substrate water is inherent to the O 2 -evolving catalytic site in the S 3 state. However, the fast phase of exchange became somewhat slower (by a factor of ϳ2) in NaClwashed membrane fragments and core complexes from spinach in which the 16-and 23-kDa extrinsic proteins have been removed, compared with the corresponding rate for the intact samples. For CaCl 2 -washed membrane fragments in which the 33-kDa manganese stabilizing protein (MSP) has also been removed, the fast phase of exchange slowed down even further (by a factor of ϳ3). Interestingly, the slow phase of exchange was little affected in the samples from spinach. For core complexes prepared from Synechocystis PCC 6803 and Synechococcus elongatus, the fast and slow exchange rates were variously affected. Nevertheless, within the experimental error, nearly the same exchange rates were measured for thylakoid samples made from wild type and an MSP-lacking mutant of Synechocystis PCC 6803. This result could indicate that the MSP has a slightly different function in eukaryotic organisms compared with prokaryotic organisms. In all samples, however, the differences in the exchange rates are relatively small. Such small differences are unlikely to arise from major changes in the metal-ligand structure at the catalytic site. Rather, the observed differences may reflect subtle long range effects in which the exchange reaction coordinates become slightly altered. We discuss the results in terms of solvent penetration into photosystem II and the regional dielectric around the catalytic site.The oxidation of water during photosynthesis is catalyzed by the membrane-bound pigment protein complex photosystem II (PSII).1 In the net reaction, four electrons, four protons, and one molecule of O 2 are liberated from the splitting of two water molecules. A key insight into the reaction mechanism was the observation that the O 2 produced in brief, saturating light flashes follows a periodicity of four (1). The period four phenomenon is now universally interpreted in terms of the S-state model, in which the catalytic site cycles through five intermediary S n states (n ϭ 0 -4) (2). Beginning in S 0 and traversing to S 4 , each S n state is driven forward by a single quantum event at the PSII reaction center. Upon reaching the S 4 state (which may be equivalent to S 3 Y Z ⅐ ) O 2 is released, S 0 is regenerated, and the cycle begins anew. The catalytic site for water oxidation involves an inorganic metal cluster consisting of four manganese ions, one Ca 2ϩ ion, possibly one Cl Ϫ ion, and the redox-active Tyr-161 resid...

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Stoichiometry of Proton Release from the Catalytic Center in Photosynthetic Water Oxidation

Cited by 154 publications

References 40 publications

Computational insights into the O2-evolving complex of photosystem II

Computational insights into the O2-evolving complex of photosystem II

Misses during Water Oxidation in Photosystem II Are S State-dependent

Substrate Water Exchange in Photosystem II Depends on the Peripheral Proteins

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