J. G. Morris

Transmembrane Respiration-driven H+ Translocation is Unimpaired in an eup Mutant of Escherichia coli

Summary: Respiration-driven H+ translocation has been examined in an eup (‘energy uncoupled phenotype’) mutant of Escherichia coli and compared with that observed in its otherwise isogenic wildtype parent. Respiration-driven H+ translocation was unimpaired in the eup mutant strain. It appears that the role of the eup gene product lies in the utilization of energized protons pumped across the E. coli cytoplasmic membrane.

Butyricin 7423 and the membrane H+-ATPase of Clostridium pasteurianum

The bacteriocin butyricin 7423 inhibited the activity of the membrane H+-ATPase (BF0, F1) of vegetative cells of Clostridium pasteurianum but not that of its soluble BF1 component. In vitro studies with the H+-ATPases of mutant strains selected for diminished sensitivity (a) to butyricin 7423 and (b) to dicyclohexylcarbodi-imide, confirmed that butyricin 7423 interacts with the BF0 component of this enzyme complex. Even so, certain other mutant strains displaying decreased sensitivity to butyricin 7423 possessed H+-ATPases which in vitro showed undiminished sensitivity to inhibition by the bacteriocin. Furthermore, from the changes in intracellular ATP concentration and in the rates and net extent of efflux of intracellular 86Rb+ ions that were provoked by exposure of the parent and several of the mutant strains to butyricin 7423, it was concluded that its primary bactericidal action was not attributable to stoichiometric inhibition of the membrane H+-ATPase. High extracellular concentrations of K+ ions enabled Cl. pasteurianum to survive exposure to low concentrations of this membrane-active bacteriocin.