The role of the `Rieske' iron sulfur protein in the hydroquinone oxidation (QP) site of the cytochrome bc 1 complex

FEBS Letters

Link, Thomas A¹ 

[1]Universitätsklinikum Frankfurt, ZBC, Institut für Biochemie I, Molekulare Bioenergetik, Theodor-Stern-Kai 7, Haus 25B, D-60590 Frankfurt/Main, Germany

关键词: Cytochrome bc 1 complex;    `Rieske' iron sulfur protein;    Hydroquinone oxidation;    Q cycle;    Semiquinone stability;    Affinity change;    CD;    circular dichroism;    ENDOR;    electron nuclear double resonance;    EPR;    electron paramagnetic resonance;    ESEEM;    electron spin echo envelope modulation;    FT-IR;    Fourier-transform infrared spectroscopy;    ISF;    `Rieske' iron sulfur fragment of the bc 1 complex;    QA;    QB site;    primary and secondary quinone sites of the bacterial photosynthetic reaction centers;    respectively;    QN;    QP site;    quinone reduction and hydroquinone oxidation sites of the bc 1 complex;    respectively;   

DOI  :  10.1016/S0014-5793(97)00772-2

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

The essential reaction in the widely accepted protonmotive Q-cycle mechanism of the bc ₁ complex is the bifurcation of the electron flow during hydroquinone oxidation at the hydroquinone oxidation (Q_P) site formed by the `Rieske' iron sulfur protein and by the heme b <sub>L</sub> domain of cytochrome b. The `Rieske' [2Fe-2S] cluster has a unique structure containing two exposed histidine ligands, which are the binding site for quinones. The affinity of the `Rieske' cluster for quinones increases several orders of magnitude upon reduction; this will stabilize semiquinone at the Q_P site. Based on this affinity change, a reaction scheme is presented which can explain the bifurcation of the electron flow without invoking highly unstable semiquinone species.

【 授权许可】

Unknown