Jun 1, 1976

The electrochemical gradient of protons and its relationship to active transport in Escherichia coli membrane vesicles

Proceedings of the National Academy of Sciences of the United States of America
S RamosH R Kaback


Membrane vesicles isolated from E. coli generate a trans-membrane proton gradient of 2 pH units under appropriate conditions when assayed by flow dialysis. Using the distribution of weak acids to measure the proton gradient (deltapH) and the distribution of the lipophilic cation triphenyl-methylphosphonium to measure the electrical potential across the membrane (delta psi), the vesicles are shown to generate an electrochemical proton gradient (deltamuH+) of approximately-180 mV at pH 5.5 in the presence of ascorbate and phenazine methosulfate, the major component of which is a deltapH of about -110mV. As external pH is increased, deltapH decreases, reaching 0 at pH 7.5 and above, while delta psi remains at about-75 mV and internal pH remains at pH 7.5. Moreover, the ability of various electron donors to drive transport is correlated with their ability to generate deltamuH+. In addition, deltapH and delta psi can be varied reciprocally in the presence of valinomycin and nigericin. These data and others (manuscript in preparation) provide convincing support for the role of chemiosmotic phenomena in active transport.

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Mentioned in this Paper

Tissue Membrane
Alkalescens-Dispar Group
Resting Potentials
Carbonyl Cyanide m-Chlorophenyl Hydrazone
Cell-Free System
Hydrogen-Ion Concentration
Acetic Acids

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