Properties of the chloride-depleted oxygen-evolving complex of photosystem II studied by electron paramagnetic resonance

Journal Article · Tue Feb 13 04:00:00 EST 1996 · Biochemistry (Eaton)

DOI:https://doi.org/10.1021/bi9514471· OSTI ID:494244

Vliet, P van ^[1]; Rutherford, A W ^[1]

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1. CEA Saclay, Gif-sur-Yvette (France)

The effects of different Cl{sup -} depletion treatments in photosystem II (PS-II)-enriched membranes have been investigated by electron paramagnetic resonance (EPR) spectroscopy and by measurements of oxygen-evolving activity. The results indicated that the oxygen-evolving complex of PS-II exhibits two distinct Cl{sup -}-dependent properties. (1) After Cl{sup -}-free washes at pH 6.3, a reversibly altered distribution of structural states of PS-II was observed, manifested as the appearance of a g = 4 EPR signal from the S{sub 2} state in a significant fraction of centers (20-40%) at the expense of the S{sub 2} multiline signal. In addition, small but significant changes in the shape of the S{sub 2} multiline EPR signal were observed. Reconstitution of Cl{sup -} to Cl{sup -}-free washed PS-II rapidly reversed the observed effects of the Cl{sup -}-free washing. The anions, SO{sub 4}{sub 2-} and F{sup -}, which are often used during Cl{sup -} depletion treatments, had no effect on the S{sub 2} EPR properties of PS-II under these conditions in the absence or presence of Cl{sup -}. Flash experiments and measurements of oxygen evolution versus light intensity indicated that the two structural states observed after the removal of Cl{sup -} at pH 6.3 originated from oxygen-evolving centers exhibiting a lowered quantum yield of water oxidation. (2) Depletion of O{sup -} in PS-II by pH 10 treatment reversibly inhibited the oxygen-evolving activity to {approx}15%. The pH 10 treatment depleted the Cl{sup -} from a site which is considered to be equivalent to that studied in most earlier work on Cl{sup -}-depleted PS-II. The S{sub 2} state in pH 10/Cl{sup -}-depleted PS-II was reversibly modified to a state from which no S{sub 2} multiline EPR signal was generated and which exhibited an intense S{sub 2} g = 4 EPR signal corresponding to at least 40% of the centers but possibly to a much larger fraction of centers. 73 refs., 10 figs.

• OSTI ID: 494244
• Journal Information: Biochemistry (Eaton), Journal Name: Biochemistry (Eaton) Journal Issue: 6 Vol. 35; ISSN 0006-2960; ISSN BICHAW
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
55 BIOLOGY AND MEDICINE
BASIC STUDIES
ANIONS
CHLORINE
ELECTRON SPIN RESONANCE
FLUORINE
OXIDATION
PH VALUE
PHOTOSYNTHESIS
PHOTOSYNTHETIC MEMBRANES
SULFATES
WATER