Purification of the rat-liver mitochondrial dicarboxylate carrier by affinity chromatography on immobilized malate...

The dicarboxylate carrier of rat-liver mitochondria, extracted by Triton X-100 and partially purified by hydroxylapatite chromatography, was retained by malate dehydrogenase immobilized on Sepharose gel, and eluted with 0.4 M NaCl. SDS-polyacrylamide gel electrophoresis of the eluate showed a predominant peptide band with an M(r) of 28,000. The purified protein, incorporated into liposomes, mediated a butylmalonate sensitive malonate(out)/malate(in) exchange that was inhibited by p-chloromercuriphenylsulfonate. Sulfate, malate and phosphate decreased the rate of exchange. The highly purified protein displayed all the properties of the dicarboxylate carrier. Moreover, the results suggest a possible functional interaction between mitochondrial carrier protein and malate dehydrogenase.