Part of the ABC transporter complex DrrABC involved in doxorubicin resistance. Responsible for energy coupling to the transport system. Binds ATP. Inhibited by reserpine. The complex is composed of two ATP-binding proteins (DrrA) and two transmembrane proteins (DrrB and DrrC). Belongs to the ABC transporter superfamily. Drug exporter-1 (DrugE1) (TC 3.A.1.105) family.