The Metal Centers of the Photosynthetic Oxygen‐evolving Complex *

Dismukes, G. Charles

doi:10.1111/j.1751-1097.1986.tb05598.x

Cited by 204 publications

(75 citation statements)

References 109 publications

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“…Only a manganese dimer was considered to be functional. The mixed valence states in S 0 and S 2 (spin ϭ 1 ⁄2) are in agreement with an EPR multiline signal in S 0 (41,42) and S 2 (43). Valence states of the manganeses have also been derived from x-ray absorption shifts at the manganese-K-edge (37-40) indicating manganese oxidations up to S 3 .…”

Section: Resultsmentioning

confidence: 55%

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

Schlodder

Witt

1999

Journal of Biological Chemistry

154

137

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The catalytic center (CC) of water oxidation in photosystem II passes through four stepwise increased oxidized states (S 0 -S 4 ) before O 2 evolution takes place from 2H 2 O in the S 4 3 S 0 transition. The pattern of the release of the four protons from the CC cannot be followed directly in the medium, because proton release from unknown amino acid residues also takes place. However, pH-independent net charge oscillations of 0:0:1:1 in S 0 :S 1 :S 2 :S 3 have been considered as an intrinsic indicator for the H ؉ release from the CC. The net charges have been proposed to be created as the charge difference between electron abstraction and H ؉ release from the CC. Then the H ؉ release from the CC is 1:0:1:2 for the S 0 3 S 1 3 S 2 3 S 3 3 S 0 transition. Strong support for this conclusion is given in this work with the analysis of the pH-dependent pattern of H ؉ release in the medium measured directly by a glass electrode between pH 5.5 and 7.2. Improved and crystallizable photosystem II core complexes from the cyanobacterium Synechococcus elongatus were used as material. The pattern can be explained by protons released from the CC with a stoichiometry of 1:0:1:2 and protons from an amino acid group (pK Ϸ 5.7) that is deprotonated and reprotonated through electrostatic interaction with the oscillating net charges 0:0:1:1 in S 0 :S 1 :S 2 :S 3 . Possible water derivatives that circulate through the S states have been named.

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Section: Resultsmentioning

confidence: 55%

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

Schlodder

Witt

1999

Journal of Biological Chemistry

154

137

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“…7), we conclude that Ca from this site in our spinach 17,24 kD-less PSII membranes has been dissociated during preparation possibly as a consequence of modification of the site, and/or that Ca at the site became dissociated during assay. We favor the first alternative based on (11,13,18 …”

mentioning

confidence: 99%

“…Parallel research has been directed towards identifying which poly- ' peptides ligate Ca2", the polynuclear Mn complex, and Cl-, elements known to be essential for 02 evolution (11,13,18). It seems clear that the 17,24 kD PSII extrinsic polypeptides are not directly required in the ligation of the polynuclear Mn complex (11,13,18,34) or for cycling of the S-states2 of 02 evolution (12,(35)(36)(37). It also is apparent (11,13,18,19) that these polypeptides somehow modulate the concentration of Clrequired for the S2-S3 (20,25,36,45) or the S3--(S4)--S0 + 02 transitions.…”

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confidence: 99%

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Studies on 17,24 kD Depleted Photosystem II Membranes

Cammarata

Cheniae²

1987

Plant Physiol.

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Analyses were made of the effects of extraction of the 17,24 kilodalton extrinsic proteins from spinach versus wheat photosystem II (PSII) membranes on Ca abundance and 02 evolution capacity determined in the absence and presence of either ClO or Ca22. Extraction of these proteins from spinach PSII routinely diminished steady state 02 evolution by about 70% when assayed in the presence ofsufficient Cl1. Additionally, 02 evolution of 17,24 kilodalton-less spinach PSI1 membranes showed about 2-fold more enhancement by Ca22 than by Cl-during assay. When the same extraction and assay procedures were applied to wheat PSII membranes, we observed, in contrast to 17,24 kilodalton-less spinach PSII, only about 50% inhibition of 02 evolution and about 2-fold greater enhancement by Cl-than by Ca21. Irrespective of differences in the magnitude of enhancement of 02 evolution by Ca2' versuC a-in spinach versus wheat, the K., values for Cl-(about 1.7 millimolar) and Ca2l (about 1.5 millimolar) were similar for both type preparations. The abundance of Ca specifically associated with fully functional PSII (about 2 and about 3 Ca/200 chlorophyll for spinach and wheat, respectively) was diminished to about 1 per 200 chlorophyll upon 17.24 kilodalton protein depletion. Further treatment of wheat 17,24 kilodalton-less PSII in darkness with 2 molar NaClI/ millimolar ethyleneglycol-bis(O-aminoethyl ether)-N,N'-tetraacetic acid/20 micromolar A231872 made 02 evolution highly dependent on Ca2 addition, much like the 17,24 kilodaltonless spinach PSII. Analyses of this Ca2' effect on 02 evolution revealed both high (K. about 65 micromolar) and low (K. about 1.5 millimolar) affinity Ca2 sites in wheat 17,24 kilodalton-less PSII. The results suggest that during 17,24 kilodalton extraction by NaCl, spinach PSII is more susceptible than wheat PSII to loss of high affinity Ca and irreversible inhibition of 02 evolution.The realization of 02 evolving everted thylakoid vesicles (1, 21) and Triton X-100 prepared PSII membranes (3, 24), also having everted membrane orientation (14,24), has led to intensive research focused on defining the polypeptides essential for efficient functioning of the PSII/water oxidizing complex. Parallel research has been directed towards identifying which poly- 90% (4-7, 15, 16, 21, 25, 27) when determined in the presence of saturating concentrations of Cl-. Subsequently, it was shown (6,7,15,16) that addition of 10 to 20 mM Ca2+ to 17,24 kDless, Cl-sufficient spinach PSII membranes increased rates of 02 evolution as much as 4-to 6-fold to rates sometimes nearly equivalent to those observed with unextracted membranes. However, no Ca2' additions were necessary to observe substantial period-4 oscillations of the S-states with only about 25% disconnection of the S-state complexes from PSII traps (12).Conceivably, at least some of the rather large variability in extent of loss of 02 evolution following depletion of the 17,24 kD proteins could reflect inadvertent dissociation of high affinity Ca2`during extraction....

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“…They have been attributed to intervalence electronic transitions within a mixed-valent Mn cluster (Dismukes & Mathis, 1984;Dismukes, 1986). The absorption changes appear upon S 2 formation, remain unchanged on S3 formation, and decrease on So formation.…”

Section: Near-irmentioning

confidence: 99%

Structural oxidation state studies of the manganese cluster in the oxygen evolving complex of photosystem II

Liang¹

1994

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The Metal Centers of the Photosynthetic Oxygen‐evolving Complex *

Cited by 204 publications

References 109 publications

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

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

Studies on 17,24 kD Depleted Photosystem II Membranes

Structural oxidation state studies of the manganese cluster in the oxygen evolving complex of photosystem II

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