Asymmetric binding of the primary acceptor quinone in reaction centers of the photosynthetic bacterium Rhodobacter sphaeroides R26, probed with Q‐band (35 GHz) EPR spectroscopy

FEBS Letters

Raap, Jan¹  Gast, Peter²  Spoyalov, Andrej P.³  Hoff, Arnold J.²  Lugtenburg, Johan¹  van Liemt, Willem B.S.¹  van den Brink, Johan S.² 

[1] Leiden Institute of Chemistry, Gorleaus Laboratories, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands;Department of Biophysics, Huygens Laboratory, Leiden University, P.O. Box 9504, 2300 RA Leiden, The Netherlands;Institute of Chemical Kinetics and Combustion, Russian Academy of Sciences, Novosibirsk, 630090, Russian Federation

关键词: Reaction center;    Quinone;    EPR;    13C-hyperfine coupling;    Photosynthesis;    Rhodobacter sphaeroides R26;    RC;    reaction center;    Rb.;    Rhodobacter;    QA;    primary acceptor quinone;    QB;    secondary acceptor quinone;    UQ;    ubiquinone;    MAS;    magic angle spinning;    FTIR;    Fourier-transform infra-red;    ENDOR;    electron-nuclear double resonance;    EPR;    electron paramagnetic resonance;    ESP;    electron spin polarisation;   

DOI  :  10.1016/0014-5793(94)01047-1

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

The reaction center (RC)-bound primary acceptor quinone Q_A of the photosynthetic bacterium Rhodobacter sphaeroides R26 functions as a one-electron gate. The radical anion Q^•− _A is proposed to have an asymmetric electron distribution, induced by the protein environment. We replace the native ubiquinone-10 (UQ10) with specifically ¹³C-labelled UQ10, and use Q-band (35 GHz) EPR spectroscopy to investigate this phenomenon in closer detail. The direct observation of the ¹³C-hyperfine splitting of the g _z-component of UQ10^•− _A in the RC and in frozen isopropanol shows that the electron spin distribution is symmetric in the isopropanol glass, and asymmetric in the RC. Our results allow qualitative assessment of the spin and charge distribution for Q^•− _A in the RC. The carbonyl oxygen of the semiquinone anion nearest to the S = 2 Fe²⁺-ion and Q_B is shown to acquire the highest (negative) charge density.

【 授权许可】

Unknown