A complex for the transport of metabolites into the cell, consisting of 5 subunits: two ATP-binding subunits, two membrane spanning subunits, and one substrate-binding subunit. In organisms with two membranes, the substrate-binding protein moves freely in the periplasmic space and joins the other subunits only when bound with substrate. In organisms with only one membrane the substrate-binding protein is tethered to the cytoplasmic membrane and associated with the other subunits. Transport of the substrate across the membrane is driven by the hydrolysis of ATP.