Alteration of the structure and function of photosystem I by Pb2

•Pb2+ modified protein structure in PSI submembrane fractions.•Binding constant, binding ratio and binding site of Pb2+ were determined.•An inhibitory site at or near plastocyanine is proposed. The toxic effects of Pb2+ on photosynthetic electron transport were studied in photosystem I (PSI) submemb...

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Published inJournal of photochemistry and photobiology. B, Biology Vol. 123; pp. 41 - 47
Main Authors Belatik, Ahmed, Hotchandani, Surat, Tajmir-Riahi, Heidar-Ali, Carpentier, Robert
Format Journal Article
LanguageEnglish
Published Switzerland Elsevier B.V 05.06.2013
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Summary:•Pb2+ modified protein structure in PSI submembrane fractions.•Binding constant, binding ratio and binding site of Pb2+ were determined.•An inhibitory site at or near plastocyanine is proposed. The toxic effects of Pb2+ on photosynthetic electron transport were studied in photosystem I (PSI) submembrane fractions isolated from spinach. Structural and spectroscopic analysis using FTIR, fluorescence and X-ray photoelectron spectroscopy (XPS) showed that Pb2+ binds with proteins via oxygen and nitrogen atoms with an overall binding constant of KPb-PSI=4.9×103 (±0.2) M−1 and the number of bound Pb2+ cation was 0.9 per PSI complex. Pb2+ binding altered the protein conformation indicating a partial protein destabilization. Electron transport and P700 photooxidation/reduction measurements showed that the interaction of Pb2+ cations with PSI produced a donor side limitation of electron transport presumably due to Pb2+ binding to or in the vicinity of plastocyanin.
ISSN:1011-1344
1873-2682
DOI:10.1016/j.jphotobiol.2013.03.010