Electrogenic proton transfer in Rhodobacter sphaeroides reaction centers: effect of coenzyme Q10 substitution by decylubiquinone in the QB binding site

FEBS Letters

Semenov, Alexey Y¹  Gopta, Oxana A¹  Bloch, Dmitry A¹ 

[1] Department of Bioenergetics, A.N. Belozersky Institute of Physico-Chemical Biology, Building ‘A’, Moscow State University, Vorobyevy Gory, Moscow 119899, Russia

关键词: Chromatophore;    Electrogenic reaction;    Photosynthetic reaction center;    Ubiquinone binding site;    Proton transfer;    Rhodobacter sphaeroides;    RC;    reaction center;    UQ;    coenzyme Q10 (2;    3-dimethoxy-5-methyl-6-decaisoprenyl-1;    4-benzoquinone);    dQ;    decylubiquinone (2;    3-dimethoxy-5-methyl-6-n-decyl-1;    4-benzoquinone);    Δψ;    transmembrane electric potential;    E a;    activation energy;    τ;    relaxation time constant;   

DOI  :  10.1016/S0014-5793(01)02537-6

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

An electrometric technique was used to investigate the effect of coenzyme Q₁₀ (UQ), substitution by decylubiquinone (dQ) at the Q_B binding site of reaction centers (UQ-RC and dQ-RC, respectively) on the electrogenic proton transfer kinetics upon Q_B reduction in Rhodobacter sphaeroides chromatophores. Unlike dQ-RC, the kinetics of the second flash-induced proton uptake in UQ-RC clearly deviated from the mono-exponential one. The activation energy (about 30 kJ/mol) and the pH profile of the kinetics in dQ-RC were similar to those in UQ-RC, with the power law approximation used in the latter case. The interpretation of the data presumed the quinone translocation between the two binding positions within the Q_B site. It is proposed that the native isoprenyl side chain (in contrast to decyl chain) favors the equilibrium binding of neutral quinone at the redox-active ‘proximal’ position, but causes a higher barrier for the hydroquinone movement from ‘proximal’ to ‘distal’ position.

【 授权许可】

Unknown