Each of the two sub-units in a DASS transporter contains a transport domain (yellow) that is mobile, and a scaffold domain (blue) that is anchored within the plasma membrane of the cell (green). When the transporter is in an outward-facing state (left) two carboxylate ions outside the cell (such as the succinate ion shown here) can each bind to one transport domain and be dragged across the membrane and into the cell by the transport domain as it slides along the scaffold domain. This leaves the transporter is in an inward-facing state (right). In cotransporters the positive charges of two sodium ions in the transport domain have an important role in trafficking carboxylate ions through the membrane; in antiporters/exchangers two positively charged residues have a similar role in the trafficking process. DASS: divalent anion/sodium symporter.