Responsible for the transport of dicarboxylates such as succinate, fumarate, and malate from the periplasm across the inner membrane. This transport system plays an important role in the energy supply of rhizobium-legume symbionts. By succinate, fumarate, and malate. Belongs to the dicarboxylate/amino acid:cation symporter (DAACS) (TC 2.A.23) family. The topology shown here is that reported by PubMed:8232193. It contradicts that predicted by TM prediction programs and which has been used in orthologous entries.