Protein and substrate coordination to the manganese cluster in the photosynthetic water oxidizing complex: nitrogen 15 and proton ENDOR spectroscopy of the S2 state multiline signal in the thermophilic cyanobacterium Synechococcus elongatus

Tang, Xiao-Song; Sivaraja, M.; Dismukes, G. Charles

doi:10.1021/ja00059a037

Cited by 67 publications

(103 citation statements)

References 2 publications

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“…The absence of the 17 and 23 kDa proteins in the core complex preparation has no effect on the appearance of the EPR signals, tH-ENDOR experiments performed at two different field positions of the $2 state multiline signal of core complexes permitted the resolution of four hyperfine (hf) splittings. The hf coupling constants obtained are 4.0, 2.3, 1.1 and 0.6 MHz, in good agreement with results that were previously reported (Tang et al (1993) J Am Chem Soc 115: 2382-2389). The intensities of all four line pairs belonging to these hf couplings are diminished in D20.…”

supporting

confidence: 91%

“…Furthermore, ENDOR signals obtained from the MLS are reported for PS II core complexes. These signals are compared with those obtained in earlier studies by our group (Zweygart et al 1992) and other laboratories (Kawamori et al 1989;Tang et al 1993). The study of Khangulov et al (1993) presents a model that allows the evaluation of effective hyperfine couplings along the magnatic field axis for the Mn(III)Mn(IV) complex in catalase.…”

Section: Introductionmentioning

confidence: 90%

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EPR and ENDOR studies of the water oxidizing complex of Photosystem II

et al. 1996

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A comparative study of X-band EPR and ENDOR of the S2 state of photosystem II membrane fragments and core complexes in the frozen state is presented. The S2 state was generated either by continuous illumination at T=200 K or by a single turn-over light flash at T=273 K yielding entirely the same S2 state EPR signals at 10 K. In membrane fragments and core complex preparations both the multiline and the g=4.1 signals were detected with comparable relative intensity. The absence of the 17 and 23 kDa proteins in the core complex preparation has no effect on the appearance of the EPR signals. (1)H-ENDOR experiments performed at two different field positions of the S2 state multiline signal of core complexes permitted the resolution of four hyperfine (hf) splittings. The hf coupling constants obtained are 4.0, 2.3, 1.1 and 0.6 MHz, in good agreement with results that were previously reported (Tang et al. (1993) J Am Chem Soc 115: 2382-2389). The intensities of all four line pairs belonging to these hf couplings are diminished in D2O. A novel model is presented and on the basis of the two largest hfc's distances between the manganese ions and the exchangeable protons are deduced. The interpretation of the ENDOR data indicates that these hf couplings might arise from water which is directly ligated to the manganese of the water oxidizing complex in redox state S2.

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supporting

confidence: 91%

Section: Introductionmentioning

confidence: 90%

EPR and ENDOR studies of the water oxidizing complex of Photosystem II

et al. 1996

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“…A number of S 2 -state ENDOR and ESEEM studies have found no direct evidence for strongly dipolar-coupled exchangeable hydrogen nuclei such as expected from Mn-coordinated waters (34,87,89). However, we have had success with observing such strongly coupled hydrogen nuclei, both with 1 H-pulsed ENDOR and 2 H-pulsed ENDOR and ESEEM.…”

Section: Substrate and Inhibitor Bindingmentioning

confidence: 83%

Pulsed and Parallel-Polarization EPR Characterization of the Photosystem II Oxygen-Evolving Complex

Britt

and

Campbell

2000

Annu. Rev. Biophys. Biomol. Struct.

127

120

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Photosystem II uses visible light to drive the oxidation of water, resulting in bioactivated electrons and protons, with the production of molecular oxygen as a byproduct. This water-splitting reaction is carried out by a manganese cluster/tyrosine radial ensemble, the oxygen -evolving complex. Although conventional continuous-wave, perpendicular -polarization electron paramagnetic resonance (EPR) spectroscopy has significantly advanced our knowledge of the structure and function of the oxygen-evolving complex, significant additional information can be obtained with the application of additional EPR methodologies. Specifically, parallel-polarization EPR spectroscopy can be use to obtain highly resolved EPR spectra of integer spin Mn species, and pulsed EPR spectroscopy with electron spin echo-based sequences, such as electron spin echo envelope modulation and electron spin echo-electron nuclear double resonance, can be used to measure weak interactions obscured in continuous-wave spectroscopy by inhomogeneous broadening.

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“…Analyses of the proton hy-perfine splitting obtained from ENDOR measurements should also provide information on the coordination of water molecules to the manganese cluster. At present, the existing data suggest that the shortest distance between manganese and protons is in the range of 3.2-3.6 A in redox state S 2 (Zweygart et al 1992, Tang et al 1993. However, it has to be emphasized that these calculations are strongly model dependent.…”

Section: Protein Matrix and Coordination Sphere Of The Manganese Clustermentioning

confidence: 98%

“…On the other hand, N-containing ligands in the first coordination sphere can be detected via ENDOR spectroscopy. Data of Tang et al (1993) provide evidence for the existence of one (or two?) nitrogens (possibly from one His-residue) in the first coordination sphere of the redox active Mn.…”

Section: Protein Matrix and Coordination Sphere Of The Manganese Clustermentioning

confidence: 99%

Water cleavage by solar radiation?an inspiring challenge of photosynthesis research

Ренгер¹

1993

Photosynth Res

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Solar energy exploitation by photosynthetic water cleavage is of central relevance for the development and sustenance of all higher forms of living matter in the biosphere. The key steps of this process take place within an integral protein complex referred to as Photosystem II (PS II) which is anisotropically incorporated into the thylakoid membrane. This minireview concentrates on mechanistic questions related to i) the generation of strongly oxidizing equivalents (holes) at a special chlorophyll a complex (designated as P680) and ii) the cooperative reaction of four holes with two water molecules at a manganese containing unit WOC (water oxidizing complex) resulting in the release of molecular oxygen and four protons. The classical work of Pierre Joliot and Bessel Kok and their coworkers revealed that water oxidation occurs via a sequence of univalent oxidation steps including intermediary redox states Si (i = number of accumulated holes within the WOC). Based on our current stage of knowledge, an attempt is made a) to identify the nature of the redox states Si, b) to describe the structural arrangement of the (four) manganese centers and their presumed coordination and ligation within the protein matrix, and c) to propose a mechanism of photosynthetic water oxidation with special emphasis on the key step, i.e. oxygen-oxygen bond formation. It is assumed that there exists a dynamic equilibrium in S3 with one state attaining the nuclear geometry and electronic configuration of a complexed peroxide. This state is postulated to undergo direct oxidation to complexed dioxygen by univalent electron abstraction with YZ (ox) and simultaneous internal ligand to metal charge transfer.Key questions on the mechanism will be raised. The still fragmentary answers to these questions not only reflect our limited knowledge but also illustrate the challenges for future research.

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Protein and substrate coordination to the manganese cluster in the photosynthetic water oxidizing complex: nitrogen 15 and proton ENDOR spectroscopy of the S2 state multiline signal in the thermophilic cyanobacterium Synechococcus elongatus

Cited by 67 publications

References 2 publications

EPR and ENDOR studies of the water oxidizing complex of Photosystem II

EPR and ENDOR studies of the water oxidizing complex of Photosystem II

Pulsed and Parallel-Polarization EPR Characterization of the Photosystem II Oxygen-Evolving Complex

Water cleavage by solar radiation?an inspiring challenge of photosynthesis research

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