Anion transporter that carries out the exchange of divalent oxalate with monovalent formate, the product of oxalate decarboxylation, at the plasma membrane, and in doing so catalyzes the vectorial portion of a proton-motive metabolic cycle that drives ATP synthesis. Monomer. The protein has a two-fold symmetry axis, with a central cavity which may be associated with substrate transport. Residues contributed from seven transmembrane helices probably line the substrate transport pathway. Its velocity of transport is the highest one known so far among transporters of organic molecules. Belongs to the major facilitator superfamily. OFA (TC 2.A.1.11) family.