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Single point mutation in the Rieske iron–sulfur subunit of cytochrome b 6 / f leads to an altered pH dependence of plastoquinol oxidation in Arabidopsis
Author(s) -
Jahns Peter,
Graf Maria,
Munekage Yuri,
Shikanai Toshiharu
Publication year - 2002
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(02)02719-9
Subject(s) - electron transport chain , chemistry , photosystem i , thylakoid , cytochrome b6f complex , plastocyanin , electron transfer , mutant , cytochrome f , cytochrome , redox , protein subunit , p700 , biophysics , point mutation , photosystem ii , wild type , biochemistry , photosynthesis , chloroplast , photochemistry , biology , inorganic chemistry , enzyme , gene
The pgr1 mutant of Arabidopsis thaliana carries a single point mutation (P194L) in the Rieske subunit of the cytochrome b 6 / f (cyt b 6 / f ) complex and is characterised by a reduced electron transport activity at saturating light intensities in vivo. We have investigated the electron transport in this mutant under in vitro conditions. Measurements of P700 reduction kinetics and of photosynthetic electron transport rates indicated that electron transfer from cyt b 6 / f to photosystem I is not generally reduced in the mutant, but that the pH dependence of this reaction is altered. The data imply that the pH‐dependent inactivation of electron transport through cyt b 6 / f is shifted by about 1 pH unit to more alkaline pH values in pgr1 thylakoids in comparison with wild‐type thylakoids. This interpretation was confirmed by determination of the transmembrane ΔpH at different stromal pH values showing that the lumen pH in pgr1 mutant plants cannot drop below pH 6 reflecting most likely a shift of the p K and/or the redox potential of the oxidised Rieske protein.