Slow electrogenic events in the cytochrome bc 1‐complex of Rhodobacter sphaeroides The electron transfer between cytochrome b hemes can be non‐electrogenic

FEBS Letters

Mamedov, Mahir D.¹  Drachev, Lel A.¹  Mulkidjanian, Armen Ya.¹ 

[1] A.N. Belozersky Laboratory of Molecular Biology and Bioorganic Chemistry, Moscow State University, Moscow, 119899, USSR

关键词: Cytochrome bc 1 complex;    Ubiquinone;    Electrogenesis;    Electron transfer;    Rhodobacter sphaeroides;   

DOI  :  10.1016/0014-5793(91)80691-U

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

The flash-induced formation of transmembrane electric potential differences (measured by carotenoid bandshift) and redox changes of cytochrome b_h (b ₅₆₁) were monitored spectrophotometrically in Rb. sphaeroides chromatophores in a pH range from 7.5 to 10.0. It is shown that in the presence of antimycin A and at pH < 8.3 the myxothiazol-sensitive, antimycin-insensitive component of the carotenoid bandshift is kinetically coupled to cytochrome b_h reduction. The kinetics of both processes can be described by a single exponent with a rise time of about 10 ms. Alkalization of the medium (8.3 ≤ pH ≤ 9.2) causes the appearance of an additional constituent in this phase of the carotenoid response with the rise time varying in the range of 100–300 ms. With a further pH increase (pH > 9.2), the electrogenic constituent, kinetically linked to cytochrome b_h reduction, diminishes. The obtained data are discussed within the framework of the scheme, assuming that the electron transfer between b_l and b_h hemes in the bc ₁ complex is, under certain conditions, accompanied by proton transfer in the same direction.

【 授权许可】

Unknown