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

FEBS Letters

Graf, Maria²  Munekage, Yuri¹  Jahns, Peter²  Shikanai, Toshiharu¹ 

[1] Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma, Nara 630-0101, Japan;Plant Biochemistry, Heinrich-Heine-Universität Düsseldorf, Universitätsstr. 1, D-40225 Düsseldorf, Germany

关键词: Cytochrome b 6/f complex;    pH regulation;    Photosynthetic electron transport;    Plastoquinol oxidation;    Rieske iron–sulfur protein;    Arabidopsis thaliana;    cyt b 6/f;    cytochrome b 6/f complex;    ISP;    iron–sulfur protein;    PSI;    photosystem I;    PSII;    photosystem II;    WT;    wild-type;    9-AA;    9-aminoacridine;   

DOI  :  10.1016/S0014-5793(02)02719-9

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

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 pK and/or the redox potential of the oxidised Rieske protein.

【 授权许可】

Unknown