Involved in cadaverine and putrescine tolerance in stationary phase. May facilitate the efflux of both cadaverine and putrescine from the cytoplasm, reducing potentially toxic levels under certain stress conditions. Deletion mutant loses viability in stationary phase when grown in acidic medium with nitrite. Mutant is sensitive to cadaverine and putrescine but not to spermine or spermidine at pH 9. Belongs to the UPF0053 family. PaeA subfamily.