When cells of Streptococcus lactis or Escherichia coli were suspended in a potassium free medium, a membrane potential (negative inside) could be artificially generated by the addition of the potassium ionophore, valinomycin. In response to this inward directed protonmotive force, ATP synthesis catalyzed by the membrane bound ATPase (EC 184.108.40.206) was observed. The formation of ATP was not found in S. lactis that had been treated with the ATPase inhibitor, N,N' dicyclohexylcarbodiimide, nor was it observed in a mutant of E. coli lacking the ATPase. Inhibition of ATP synthesis in S. lactis was also observed when the membrane potential was reduced by the presence of external potassium, or when cells were first incubated with the proton conductor, carbonyl cyanide fluoromethoxy phenylhydrazone. These results are in agreement with predictions made by the chemiosmotic hypothesis of Mitchell.
|Original language||English (US)|
|Number of pages||5|
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|State||Published - Jan 1 1974|
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