Photoinhibition affects the non‐heme iron center in photosystem II

FEBS Letters

Gleiter, Hermann M.¹  Haag, Elisabeth¹  Renger, Gernot¹  Nugent, Jonathan H.A.² 

[1] Max-Volmer-Institute for Biophysical Chemistry, Technical University Berlin, 1000 Berlin 12, Germany;Department of Biology, Darwin Building, University College London, Gower Street, London WC1E 6BT, UK

关键词: Photosynthesis;    Photosystem II;    Photoinhibition;    Non-heme iron;    Spinacea oleracca;    PS II;    photosystem II;    QA and QB;    primary and secondary plastoquinone acceptor;    MES;    4-morpholinethane sulphonic acid;    DCBQ;    2;    6-dichloro-p-benzoquinone;    EPR;    electron paramagnetic resonance;    F0;    fluorescence level in the dark adapted state;    Fvar;    variable fluorescence;    Fmax;    maximum fluorescence;   

DOI  :  10.1016/0014-5793(92)81188-R

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Effects on the PS II acceptor side caused by exposure to strong white light (180 W/m²) of PS II membrane fragments (spinach) at pH 6.5 and 0°C were analyzed by measuring low temperature EPR signals and flash-induced transient changes of the flourescence quantum yield. The following results were obtained: (a) the extent of the light induced g = 1.9 EPR signal as a measure of photochemical Fe²⁺Q⁻ _A formation declines with progressing photoinhibition. The half-life of this effect is independent of the absence or presence of an exogenous electron acceptor during the photoinhibitory treatment; (b) in samples photoinhibited in the absence of an electron acceptor and subsequently incubated with K₃[Fe(CN)₆] in the dark, the extent of the g = 8 EPR signal (reflecting the oxidized Fe₃₊ form of the endogenous non-heme iron center) and of the flash-induced change of the flourescence yield (as a measure of fast electron transfer from Q⁻ _A to Fe³⁺ after the first flash; [see (1992) Photosynth. Res. 31, 113–126] exhibits the same dependence on photoinhibition time as the g = 1.9 EPR signal; (c) in samples photoinhibited in the presence of an exogenous electron acceptor, the signals reflecting Fe³⁺-formation and fast electron transfer from Q⁻ _A to Fe³⁺ decline faster than the g = 1.9 EPR signal. These results provide for the first time direct evidence that the endogenous non-heme iron located between Q_A and Q_B is susceptible to modifications by light stress. The implications of this finding will be discussed.

【 授权许可】

Unknown