Open AccessATP synthesis in chromatophores driven by artificially induced ion gradients
Author(s) -
TURINA Paola,
MELANDRI B. Andrea,
GRÄBER Peter
Publication year - 1991
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1991.tb15808.x
Subject(s) - chemistry , electrochemical potential , diffusion , valinomycin , membrane potential , ion , electrochemistry , membrane , ion transporter , potential difference , analytical chemistry (journal) , biophysics , thermodynamics , chromatography , biochemistry , electrode , physics , biology , organic chemistry
An electrochemical potential difference for protons (μ H+ ) across the membrane of bacterial chromatophores was induced by an artificially generated pH difference (pH) and a K + /valinomycin diffusion potential, φ. The initial rate of ATP synthesis was measured with a rapid‐mixing quenched‐flow apparatus in the time range between 70 ms and 30 s after the acid–base transition. The rate of ATP synthesis depends exponentially on pH;. Increasing diffusion potentials shift the pH dependency to lower pH values. Diffusion potentials were calculated from the Goldman equation. Using estimated permeability coefficients, the rate of ATP synthesis depends only on the electrochemical potential difference of protons irrespective of the relative contribution of pH and φ.