Cell membrane polyamine/proton symporter involved in the polyamine uptake in cells. Possesses high affinity for spermidine and lower affinity for spermine and putrescine. Transports paraquat, a polyamine analog, and thus confers sensitivity to this chemical which is used as a herbicide. Plasma membrane. Expressed in seedling roots, leaves, stems, flowers and siliques. Belongs to the amino acid-polyamine-organocation (APC) superfamily. Polyamine:cation symporter (PHS) (TC 2.A.3.12) family.