Premium
ATP‐synthase of Rhodobacter capsulatus : coupling of proton flow through F 0 to reactions in F 1 under the ATP synthesis and slip conditions
Author(s) -
Feniouk Boris A.,
Cherepanov Dmitry A.,
Junge Wolfgang,
Mulkidjanian Armen Y.
Publication year - 1999
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(99)00160-x
Subject(s) - atp synthase , rhodobacter , photophosphorylation , chemiosmosis , proton , chemistry , proton transport , adenosine triphosphate , photochemistry , biophysics , biochemistry , chloroplast , enzyme , membrane , biology , mutant , physics , quantum mechanics , gene
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 F 0 F 1 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 F 0 F 1 . The proton transfer through F 0 F 1 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.