Partial Purification and Reconstitution of the α-Ketoglutarate Carrier from Corn (Zea mays L.) Mitochondria

The alpha-ketoglutarate carrier from corn shoot mitochondria (Zea mays L., B 73) was solubilized in Triton X-114 and partially purified by chromatography on hydroxyapatite and celite in the presence of cardiolipin. On SDS-gel electrophoresis, the hydroxyapatite/celite eluate showed various protein bands between 12 and 70 kilodaltons. When reconstituted into liposomes, the alpha-ketoglutarate transport protein catalyzed a phthalonate-sensitive alpha-ketoglutarate/alpha-ketoglutarate exchange. The protein was purified 60-fold with a recovery of 88% with respect to the mitochondrial extract. The protein yield was 0.6%. The properties of the reconstituted carrier, i.e. requirement for a counter-anion, substrate specificity, and inhibitor sensitivity, were similar to those of the alpha-ketoglutarate transport system as characterized in plant and animal mitochondria.