Part of the ABC transporter complex HtxBCDE involved in hypophosphite import. Responsible for energy coupling to the transport system (Probable). ATP + H2O + phosphinate(out) = ADP + H(+) + phosphate + phosphinate(in) The complex is composed of two ATP-binding proteins (HtxD), two transmembrane proteins (HtxC and HtxE) and a solute-binding protein (HtxB). Belongs to the ABC transporter superfamily. Phosphonates importer (TC 3.A.1.9.1) family.