Photoreduction of the quinone pool in the bacterial photosynthetic membrane: identification of infrared marker bands for quinol formation

FEBS Letters

Leibl, Winfried¹  Nabedryk, Eliane¹  Mezzetti, Alberto¹  Breton, Jacques¹ 

[1] Service de Bioénergétique, Bâtiment 532, CEA Saclay, 91191 Gif-sur-Yvette Cedex, France

关键词: FTIR;    Photosynthetic membrane;    Quinone pool;    Quinol;    RC;    reaction center;    Q;    quinone;    QH2;    quinol;    Qn;    2;    3-dimethoxy-5-methyl-6-polypropenyl-1;    4-benzoquinone;    QA and QB;    primary and secondary quinone electron acceptors;    respectively;    P;    primary electron donor;    FTIR;    Fourier transform infrared;   

DOI  :  10.1016/S0014-5793(03)00118-2

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

The photoreduction of the quinone (Q) pool in the photosynthetic membrane of the purple bacterium Rhodobacter sphaeroides was investigated by steady-state and time-resolved Fourier transform infrared difference spectroscopy. The results are consistent with the existence of a homogeneous Q pool inside the chromatophore membrane, with a size of around 20 Q molecules per reaction center. IR marker bands for the quinone/quinol (Q/QH₂) redox couple were recognized. QH₂ bands are identified at 1491, 1470, 1433 and 1388–1375 cm⁻¹. The 1491 cm⁻¹ band, which is sensitive to ¹H/²H exchange, is assigned to a C–C ring mode coupled to a C–OH mode. A feature at ∼1743/1720 cm⁻¹ is tentatively related to a perturbation of the carbonyl modes of phospholipid head groups induced by QH₂ formation. Complex conformational changes of the protein in the amide I and II spectral ranges are also apparent during reduction and reoxidation of the Q pool.

【 授权许可】

Unknown