Part of the ABC transporter complex PotABCD involved in spermidine/putrescine import. Responsible for energy coupling to the transport system. ATP + H2O + polyamine-[polyamine-binding protein]Side 1 = ADP + phosphate + polyamineSide 2 + [polyamine-binding protein]Side 1. The complex is composed of two ATP-binding proteins (PotA), two transmembrane proteins (PotB and PotC) and a solute-binding protein (PotD). Belongs to the ABC transporter superfamily. Spermidine/putrescine importer (TC 3.A.1.11.1) family.