Transport of fatty acid is obligatory coupled with H+ entry in spheroplasts of Escherichia coli K12.

Transport of palmitate by spheroplasts of Escherichia coli K12 was studied. [14C]Palmitate was accumulated in spheroplasts approximately 1700-fold over the extracellular concentration of unbound [14C]palmitate. Uptake of [14C]palmitate was inhibited to 13% by addition of H+ uncoupler carbonyl cyanide-m-chlorophenylhydrazone (CCCP). Spheroplasts exhibited the uptake of 9-aminoacridine depending on the addition of palmitate to the incubation mixture. The rate of [14C]palmitate uptake by the spheroplasts pre-equilibrated in a buffer at pH 7.5 or 8.0 significantly increased in comparison with the spheroplasts pre-equilibrated in a buffer at pH 7.0 when the spheroplasts were incubated at an external pH of 7.0.