secondary active transmembrane transporter activity antiporter activity GO:0015300 Reactome:R-HSA-2730692 solute:solute antiporter activity porter Reactome:R-HSA-2731002 antiport molecular_function exchanger ion antiporter activity exchange transporter activity Reactome:R-HSA-2730959 GO:0015297 solute:solute exchange Enables the active transport of a solute across a membrane by a mechanism whereby two or more species are transported in opposite directions in a tightly coupled process not directly linked to a form of energy other than chemiosmotic energy. The reaction is: solute A(out) + solute B(in) = solute A(in) + solute B(out). countertransporter activity GO:0099516