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Title

Flash-induced absorption spectroscopy studies of copper interaction with photosystem II in higher plants

AuthorsSchröder, Wolfgang P.; Arellano, Juan B. ; Bittner, Thomas; Barón Ayala, Matilde; Eckert, Hann-Jörg; Renger, Gernot
KeywordsLaser Flash Photolysis
Photosystem II
Copper
Inhibition
Issue DateDec-1994
PublisherAmerican Society for Biochemistry and Molecular Biology
CitationJournal of Biological Chemistry (1994) 269:32865-32870.
AbstractMeasurements of flash-induced absorption changes at 325, 436, and 830 nm and of oxygen evolution were performed in order to analyze in detail the inhibition of photosystem II (PS II) by Cu(II) in PS II membrane fragments from spinach. (a) The kinetics of P680+ reduction become markedly slower in the presence of 100 microM CuSO4. (b) The CuSO4- induced kinetics of P680+ reduction are dominated by a 140-160- microsecond decay. (c) The extent of these 140-160-microsecond kinetics, normalized to the overall decay, remains virtually unaffected by addition of the exogenous PS II donor, NH2OH. (d) In thoroughly dark- adapted samples the CuSO4-induced 140-160-microsecond kinetics are already observed after the first flash and remain unchanged by a train of excitation flashes. (e) The extent of P680+ and QA- formation under repetitive flash excitation is not diminished by addition of 100 microM CuSO4. (f) The induction of microsecond kinetics of P680+ reduction at the expense of ns kinetics and the inhibition of the saturation rate of oxygen evolution exhibit the same dependence on CuSO4 concentration. (g) CuSO4 also transforms the 10-20-microsecond reduction of P680+ by TyrZ in Tris-washed PS II membrane fragments into 140-160-microsecond kinetics without any effect on the extent of flash-induced P680+ formation. These results unambiguously show that Cu(II) does not affect the charge separation (P680+QA-), but instead specifically modifies TyrZ and/or its micro environment so that the electron transfer to P680+ becomes blocked.
Publisher version (URL)http://www.jbc.org/cgi/content/abstract/269/52/32865
URIhttp://hdl.handle.net/10261/11098
ISSN0021-9258
Appears in Collections:(IRNASA) Artículos
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