The roles of the extrinsic subunits in Photosystem II as revealed by EPR

Franzén, Lars‐Gunnar; Hansson, Örjan; Andréasson, Lars-Erik

doi:10.1016/0005-2728(85)90040-4

Cited by 65 publications

(28 citation statements)

References 44 publications

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“…Photosystem II-enriched thylakoid membrane fragments were prepared from fresh market spinach by Triton X-100 extraction (Berthold et al 1981), modified as described previously (Franzén et al 1985). The PSII-enriched membranes were suspended in buffer containing 0.4 M sucrose, 20 mM MES-NaOH, 15 mM NaCl, and 5 mM MgCl 2 at pH 6.3 and stored in liquid nitrogen.…”

Section: Psii Preparationmentioning

confidence: 99%

Fluoride inhibition of photosystem II and the effect of removal of the PsbQ subunit

Kuntzleman

Haddy

2009

Photosynth Res

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Photosystem II (PSII), the light-absorbing complex of photosynthesis that evolves oxygen, requires chloride for activation of the oxygen evolving complex (OEC). In this study, fluoride was characterized as an inhibitor of Cl(-)-activated oxygen evolution in higher plant PSII. It was confirmed to be primarily a competitive inhibitor in intact PSII, with Cl(-)-competitive inhibition constant K(i) = 2 mM and uncompetitive inhibition constant K'(1) = 79 mM. A pH dependence study showed that fluoride inhibition was more pronounced at lower pH values. In order to determine the location of the fluoride effect, PSII preparations lacking various amounts of the PsbQ subunit were prepared. The competitive F(-) inhibition constant and the Michaelis constant for Cl(-) activation increased with loss of the PsbQ subunit, while the uncompetitive F(-) inhibition constant was relatively insensitive to loss of PsbQ. The S(2) state EPR signals from PSII lacking PsbQ responded to Ca(2+) and Cl(-) removal and to F(-) treatment similar to intact PSII, with enhancement of the g = 4.1 signal and suppression of the multiline signal, but the effects were more pronounced in PSII lacking PsbQ. Together, these results support the interpretation that the PsbQ subunit has a role in retaining anions within the OEC.

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Section: Psii Preparationmentioning

confidence: 99%

Fluoride inhibition of photosystem II and the effect of removal of the PsbQ subunit

Kuntzleman

Haddy

2009

Photosynth Res

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“…PS II-euriched thylakoid membranes from spinach were prepared as described in [12] and suspended at 10-15 mg Chl/ml in 20 mM Mes-NaOH, pH 6.3, containing 15 mM NaCl, 5 mM MgCI2 and 400 mM sucrose.…”

Section: Preparation Of Photosynthetic Materialsmentioning

confidence: 99%

The nature of the Fe(III) EPR signal from the acceptor‐side iron in photosystem II

1989

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“…Treatments that solubilize all three extrinsic polypeptides (the 17, 23 and 33 kDa polypeptides), but not Mn, such as incubation in 1 M CaCI2, 1 M MgC12 or 2.6 M urea with 200 mM NaC1, demonstrate that Mn can remain bound in the absence of the 33 kDa polypeptide [15,24,27]. Two of the four Mn are not as stably bound in 17, 23 and 33 kDa polypeptide-depleted PSII membranes as in untreated PSII membranes however, and are eventually lost unless the medium contains a high concentration of C1- [24].…”

Section: Introductionmentioning

confidence: 99%

Formation of the S2 state and structure of the Mn complex in photosystem II lacking the extrinsic 33 kilodalton polypeptide

1987

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Electron paramagnetic resonance (EPR) spectroscopy and O2 evolution assays were performed on photosystem II (PSII) membranes which had been treated with 1 M CaCl2 to release the 17, 23 and 33 kilodalton (kDa) extrinsic polypeptides. Manganese was not released from PSII membranes by this treatment as long as a high concentration of chloride was maintained. We have quantitated the EPR signals of the several electron donors and acceptors of PSII that are photooxidized or reduced in a single stable charge separation over the temperature range of 77 to 240 K. The behavior of the samples was qualitatively similar to that observed in samples depleted of only the 17 and 23 kDa polypeptides (de Paula et al. (1986) Biochemistry25, 6487-6494). In both cases, the S2 state multiline EPR signal was observed in high yield and its formation required bound Ca(2+). The lineshape of the S2 state multiline EPR signal and the magnetic properties of the manganese site were virtually identical to those of untreated PSII membranes. These results suggest that the structure of the manganese site is unaffected by removal of the 33 kDa polypeptide. Nevertheless, in samples lacking the 33 kDa polypeptide a stable charge separation could only be produced in about one half of the reaction centers below 160 K, in contrast to the result obtained in untreated or 17 and 23 kDa polypeptide-depleted PSII membranes. This suggests that one function of the 33 kDa polypeptide is to stabilize conformations of PSII that are active in secondary electron transfer events.

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The roles of the extrinsic subunits in Photosystem II as revealed by EPR

Cited by 65 publications

References 44 publications

Fluoride inhibition of photosystem II and the effect of removal of the PsbQ subunit

Fluoride inhibition of photosystem II and the effect of removal of the PsbQ subunit

The nature of the Fe(III) EPR signal from the acceptor‐side iron in photosystem II

Formation of the S2 state and structure of the Mn complex in photosystem II lacking the extrinsic 33 kilodalton polypeptide

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