Mitochondrial antiporter which catalyzes the transport of citrate and oxoglutarate across the membrane. Also shows specificity for oxaloacetate, and to a lesser extent succinate and fumarate. Transports isocitrate, cis-aconitate and L-malate with very low efficiency. Does not show uniporter activity. Helps to maintain normal citrate levels and NADPH/NADP(+) ratios under conditions of oxidative stress. In addition, associates with the mitochondrial nucleoid and binds DNA in vitro, although the relevance of these data in vivo is unclear. Strongly inhibited by mersalyl, p-chloromercuribenzenesulfonate, mercuric chloride, N-ethylmaleimide, pyridoxal 5'-phosphate, bathophenanthroline, and tannic acid. Partially inhibited by alpha-cyanocinnamate and bromescol purple. Weakly inhibited by butylmalonate and phenylsuccinate. Not inhibited by 1,2,3-benzenetricarboxylate or carboxyatractyloside. Shows slow growth and respiration defects in minimal medium. Shows growth defects in acetate-supplemented medium; the phenotype is enhanced by addition of hydrogen peroxide (increased oxidative stress) and/or double knockout of YHM2 and ZWF1. The cytosolic NADPH/NADP(+) ratio is decreased compared to wild type; this effect is enhanced in the presence of hydrogen peroxide. The mitochondrial NADPH/NADP(+) ratio is increased, but only in the presence of hydrogen peroxide. Levels of cytosolic citrate are reduced, but only in the presence of hydrogen peroxide. Levels of cytosolic oxoglutarate are reduced, but only in the presence of hydrogen peroxide; the effect is enhanced by double knockout of YHM2 and ZWF1. Cells show a very small increase in levels of reactive oxygen species (ROS) following hydrogen peroxide treatment; in double knockouts of YHM2 and ZWF1 there is a large increase in ROS. Overexpression suppresses the temperature-sensitive growth defect of ABF2 in glucose-rich medium. Present with 2930 molecules/cell in log phase SD medium. Belongs to the mitochondrial carrier (TC 2.A.29) family. Was originally proposed to function in mitochondrial DNA replication and maintenance.