Active and resting states of the O2-Evolving Complex of photosystem II

Warren F. Beck, Julio C. De Paula, Gary W Brudvig

Research output: Contribution to journalArticle

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Abstract

During dark adaptation, a change in the O2-evolving complex (OEC) of spinach photosystem II (PSII) occurs that affects both the structure of the Mn site and the chemical properties of the OEC, as determined from low-temperature electron paramagnetic resonance (EPR) spectroscopy and O2 measurements. The S2-state multiline EPR signal, arising from a Mn-containing species in the OEC, exhibits different properties in long-term (4 h at O°C) and short-term (6 min at O°C) dark-adapted PSII membranes or thylakoids. The optimal temperature for producing this EPR signal in long-term dark-adapted samples is 200 K compared to 170 K for short-term dark-adapted samples. However, in short-term dark-adapted samples, illumination at 170 K produces an EPR signal with a different hyperfine structure and a wider field range than does illumination at 160 K or below. In contrast, the line shape of the S2-state EPR signal produced in long-term dark-adapted samples is independent of the illumination temperature. The EPR-detected change in the Mn site of the OEC that occurs during dark adaptation is correlated with a change in O2 consumption activity of PSII or thylakoid membranes. PSII membranes and thylakoid membranes slowly consume O2 following illumination, but only when a functional OEC and excess reductant are present. We assign this slow consumption of O2 to a catalytic reduction of O2 by the OEC in the dark. The rate of O2 consumption decreases during dark adaptation; long-term dark-adapted PSII or thylakoid membranes do not consume O2 despite the presence of excess reductant. The EPR-detected change in the Mn site of the OEC and the decline of the O2 consumption activity observed in PSII or thylakoid membranes occur with the same time constant. It is proposed that a structural change in the Mn site of the OEC occurs during dark adaptation, changing the electron-transport properties of the donor side of PSII and causing a conversion from an active, O2-consuming state to a resting state incapable of O2 consumption.

Original languageEnglish
Pages (from-to)3035-3043
Number of pages9
JournalBiochemistry
Volume24
Issue number12
Publication statusPublished - 1985

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Photosystem II Protein Complex
Electron Spin Resonance Spectroscopy
Paramagnetic resonance
Thylakoids
Dark Adaptation
Membranes
Lighting
Reducing Agents
Temperature
Electron transport properties
Spinacia oleracea
Electron Transport
Chemical properties
Spectrum Analysis
Spectroscopy

ASJC Scopus subject areas

  • Biochemistry

Cite this

Active and resting states of the O2-Evolving Complex of photosystem II. / Beck, Warren F.; De Paula, Julio C.; Brudvig, Gary W.

In: Biochemistry, Vol. 24, No. 12, 1985, p. 3035-3043.

Research output: Contribution to journalArticle

Beck, WF, De Paula, JC & Brudvig, GW 1985, 'Active and resting states of the O2-Evolving Complex of photosystem II', Biochemistry, vol. 24, no. 12, pp. 3035-3043.
Beck, Warren F. ; De Paula, Julio C. ; Brudvig, Gary W. / Active and resting states of the O2-Evolving Complex of photosystem II. In: Biochemistry. 1985 ; Vol. 24, No. 12. pp. 3035-3043.
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