Proton-coupled chloride transporter. Functions as antiport system and exchanges two chloride ions for 1 proton. Probably acts as an electrical shunt for an outwardly-directed proton pump that is linked to amino acid decarboxylation, as part of the extreme acid resistance (XAR) response. 2 chloride(in) + H(+)(out) = 2 chloride(out) + H(+)(in) Homodimer. Belongs to the chloride channel (TC 2.A.49) family. ClcA subfamily.