ATP‐synthase of Rhodobacter capsulatus: coupling of proton flow through F0 to reactions in F1 under the ATP synthesis and slip conditions

FEBS Letters

Junge, Wolfgang¹  Feniouk, Boris A.¹  Cherepanov, Dmitry A.¹  Mulkidjanian, Armen Y.¹ 

[1]Division of Biophysics, Faculty of Biology/Chemistry, University of Osnabrück, D-49069 Osnabrück, Germany

关键词: Membrane potential;    ATP synthesis;    Elasticity;    Proton transfer;    (Rhodobacter capsulatus);    BChl;    bacteriochlorophyll;    BSA;    bovine serum albumin;    DCCD;    N;    N′-dicyclohexylcarbodiimide;    DTT;    dithiotreitol;    FCCP;    carbonyl cyanide;    p-trifluoromethoxyphenylhydrazone;    HEPES;    4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid;    RC;    photosynthetic reaction center of purple phototrophic bacteria;    Pi;    inorganic phosphate;    μ ̃ H+;    transmembrane electrochemical potential difference of protons;    Δψ;    transmembrane electrical potential difference;   

DOI  :  10.1016/S0014-5793(99)00160-X

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

A stepwise increasing membrane potential was generated in chromatophores of the phototrophic bacterium Rhodobacter capsulatus by illumination with short flashes of light. Proton transfer through ATP-synthase (measured by electrochromic carotenoid bandshift and by pH-indicators) and ATP release (measured by luminescence of luciferin-luciferase) were monitored. The ratio between the amount of protons translocated by F₀F₁ and the ATP yield decreased with the flash number from an apparent value of 13 after the first flash to about 5 when averaged over three flashes. In the absence of ADP, protons slipped through F₀F₁. The proton transfer through F₀F₁ after the first flash contained two kinetic components, of about 6 ms and 20 ms both under the ATP synthesis conditions and under slip. The slower component of proton transfer was substantially suppressed in the absence of ADP. We attribute our observations to the mechanism of energy storage in the ATP-synthase needed to couple the transfer of four protons with the synthesis of one molecule of ATP. Most probably, the transfer of initial protons of each tetrad creates a strain in the enzyme that slows the translocation of the following protons.

【 授权许可】

Unknown