Open AccessChanges in the proton‐motive force in Escherichia coli in response to external oxidoreduction potential
Author(s) -
Riondet Christophe,
Cachon Rémy,
Waché Yves,
Alcaraz , Gérard,
Diviès Charles
Publication year - 1999
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1046/j.1432-1327.1999.00429.x
Subject(s) - chemistry , membrane , escherichia coli , membrane potential , electrochemical gradient , biophysics , proton , conductance , atpase , permeability (electromagnetism) , biochemistry , enzyme , biology , physics , mathematics , quantum mechanics , combinatorics , gene
The pH homeostasis and proton‐motive force (Δp) of Escherichia coli are dependent on the surrounding oxidoreduction potential (ORP). Only the internal pH value and, thus, the membrane pH gradient (ΔpH) component of the Δp is modified, while the membrane potential (ΔΨ) does not change in a significant way. Under reducing conditions ( E h < 50 mV at pH 7.0), E. coli decreases its Δp especially in acidic media (21% decrease at pH 7.0 and 48% at pH 5.0 for a 850‐mV ORP decrease). Measurements of ATPase activity and membrane proton conductance ( C H + m ) depending on ORP and pH have shown that the internal pH decrease is due to an increase in membrane proton permeability without any modification of ATPase activity. We propose that low ORP values de‐energize E. coli by modifying the thiol : disulfide balance of proteins, which leads to an increase in the membrane permeability to protons.