. "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)." . . "antiporter activity" . "solute:solute exchange" . "antiport" . "countertransporter activity" . "exchange transporter activity" . "exchanger" . "porter" . "solute:solute antiporter activity" . . . . . . . . . . . . . . . . . . . . . . . . .