Premium
Electrogenic proton transfer in Rhodobacter sphaeroides reaction centers: effect of coenzyme Q 10 substitution by decylubiquinone in the Q B binding site
Author(s) -
Gopta Oxana A,
Semenov Alexey Y,
Bloch Dmitry A
Publication year - 2001
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(01)02537-6
Subject(s) - rhodobacter sphaeroides , chemistry , substitution (logic) , proton , cofactor , stereochemistry , photosynthetic reaction centre , binding site , photochemistry , electron transfer , biochemistry , photosynthesis , enzyme , physics , quantum mechanics , computer science , programming language
An electrometric technique was used to investigate the effect of coenzyme Q 10 (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.