The donor side of Photosystem II as the copper-inhibitory binding site |
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Authors: | J B Arellano J J Lázaro J López-Gorgé M Barón |
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Institution: | (1) Department of Plant Biochemistry, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas (CSIC), Profesor Albareda,1, 18008 Granada, Spain |
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Abstract: | We have measured, under Cu (II) toxicity conditions, the oxygen-evolving capacity of spinach PS II particles in the Hill reactions H2OSiMo (in the presence and absence of DCMU) and H2OPPBQ, as well as the fluorescence induction curve of Tris-washed spinach PS II particles. Cu (II) inhibits both Hill reactions and, in the first case, the DCMU-insensitive H2O SiMo activity. In addition, the variable fluorescence is lowered by Cu (II). We have interpreted our results in terms of a donor side inhibition close to the reaction center. The same polarographic and fluorescence measurements carried out at different pHs indicate that Cu (II) could bind to amino acid residues that can be protonated and deprotonated. In order to reverse the Cu (II) inhibition by a posterior EDTA treatment, in experiments of preincubation of PS II particles with Cu (II) in light we have demonstrated that light is essential for the damage due to Cu (II) and that this furthermore is irreversible.Abbreviations DCMU
3-(3,4-dichlorophenyl)-1, 1-dimethyl urea
- DCIP
2,6-dichlorophenolindophenol
- DPC
1,5-diphenilcarbazide
- Fo
initial non-variable fluorescence
- FI
intermediate fluorescence yield
- Fm
maximum fluorescence yield
- Fv
variable fluorescence yield
- Mes
2,-(N-morpholino)ethanosulfonic acid
- OEC
oxygen-evolving complex
- P680
Primary electron donor chlorophyll
- Pheo
pheophytin
- PPBQ
phenyl-p-benzo-quinone
- PS II
Photosystem II
- SiMo
Silicomolybdate
- QB
secondary quinone acceptor
- QA
primary quinone aceptor
- Tris
N-tris(hydroxymethyl)amino ethane
- Tyrz
electron carrier functioning between P680 and the Mn cluster
This article is dedicated to Prof. Dr. Harmut Lichtenthaler on the occasion of his 60th birthday. |
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Keywords: | copper toxicity Photosystem II Spinacia oleracea |
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