Catalyzes both the uptake and excretion of putrescine. The uptake of putrescine is dependent on the membrane potential and the excretion involves putrescine-ornithine antiporter activity. H(+)(in) + putrescine(in) = H(+)(out) + putrescine(out) L-ornithine(out) + putrescine(in) = L-ornithine(in) + putrescine(out) Uptake activity, but not antiporter activity, is inhibited by CCCP and N-ethylmaleimide (NEM). Uptake of putrescine is inhibited by high concentrations of ornithine. Optimum pH is 6.5 for uptake activity. Optimum pH is 9.2 for antiporter activity. Monomer. Induced at low environmental pH. Part of the speFL-speF-potE operon. Belongs to the amino acid-polyamine-organocation (APC) superfamily. Basic amino acid/polyamine antiporter (APA) (TC 2.A.3.2) family.