Electroneutral antiporter that mediates the transport of adenine nucleotides through the inner mitochondrial membrane. Originally identified as an ATP-magnesium/inorganic phosphate antiporter, it also acts as a broad specificity adenyl nucleotide antiporter. By regulating the mitochondrial matrix adenine nucleotide pool could adapt to changing cellular energetic demands and indirectly regulate adenine nucleotide-dependent metabolic pathways (PubMed:15123600). Also acts as a regulator of mitochondrial calcium uptake and can probably transport trace amounts of other divalent metal cations in complex with ATP (PubMed:24430870, PubMed:28695448). In vitro, a low activity is also observed with guanyl and pyrimidine nucleotides (PubMed:15123600).
