Nature of the inhibition of the oxygen-evolving enzyme of photosystem II induced by NaCl washing and reversed by the addition of Ca/sup 2 +/ or Sr/sup 2 +/

Journal Article · Tue May 03 04:00:00 EDT 1988 · Biochemistry; (United States)

OSTI ID:5045785

Boussac, A; Rutherford, A W

The inhibition of the oxygen-evolving enzyme of photosystem II, induced by NaCl washing, has been studied by monitoring the yield of the EPR multiline signal arising from the S/sub 2/ charge storage state. After continuous illumination at 200 K, the S/sub 2/-multiline signal was present with almost the same amplitude in inhibited and Ca/sup 2 +/-reconstituted membranes. Flash illumination given at room temperature to Ca/sup 2 +/-reconstituted membranes resulted in the usual period four oscillation pattern in the amplitude of the S/sub 2/-multiline signal. In the absence of Ca/sup 2 +/, although the multiline signal was formed on the first flash and decreased on the second flash, no further increase in the signal amplitude occurred on the fifth flash. In addition, dark adaptation for 15 s of inhibited membranes that had been given three flashes resulted in the formation of the S/sub 2/-multiline signal due to deactivation of the S/sub 3/ state. These results indicate that in NaCl-washed material inhibition of S-state turnover occurs at the S/sub 3/ to S/sub 0/ transition. These results disagree with several earlier reports. Attempts have therefore been made to reconcile these reports with the present work both experimentally and be reevaluation of the earlier data. Other apparent inconsistencies in the literature are discussed in terms of differential depletion of Ca/sup 2 +/ from sites with different binding affinities. The authors speculate that these complex phenomena may be simply explained within a model in which a single Ca/sup 2 +/ specific binding site is associated with oxygen evolution and that the affinity of this site is modulated by the S states. It is also shown that reactivation by Sr/sup 2 +/ instead of Ca/sup 2 +/ induced a modified multiline signal similar to that observed in NH/sub 3/-treated photosystem II membranes.

• Research Organization: CEN de Saclay, Gif-sur-Yvette (France)
• OSTI ID: 5045785
• Journal Information: Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 27:9; ISSN BICHA
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
140505* -- Solar Energy Conversion-- Photochemical
Photobiological
& Thermochemical Conversion-- (1980-)
ALKALI METAL COMPOUNDS
ALKALINE EARTH METAL COMPOUNDS
BIOCHEMISTRY
CALCIUM CHLORIDES
CALCIUM COMPOUNDS
CALCIUM HALIDES
CHEMICAL REACTIONS
CHEMISTRY
CHLORIDES
CHLORINE COMPOUNDS
ELECTRON SPECTRA
ELECTRON SPIN RESONANCE
ELEMENTS
HALIDES
HALOGEN COMPOUNDS
INHIBITION
MAGNETIC RESONANCE
MEMBRANES
NONMETALS
OXYGEN
PHOTOCHEMICAL REACTIONS
PHOTOSYNTHESIS
PHOTOSYNTHETIC MEMBRANES
PHOTOSYNTHETIC REACTION CENTERS
RESONANCE
SODIUM CHLORIDES
SODIUM COMPOUNDS
SPECTRA
STRONTIUM CHLORIDES
STRONTIUM COMPOUNDS
SYNTHESIS