Calcium-dependent mitochondrial solute carrier. Mediates the reversible, electroneutral exchange of Mg-ATP or Mg-ADP against phosphate ions, catalyzing the net uptake or efflux of adenine nucleotides across the mitochondrial inner membrane. Nucleotide transport is inactive when cytosolic calcium levels are low, and is activated by an increase in cytosolic calcium levels. May play a role in protecting cells against oxidative stress-induced cell death, probably by promoting the formation of calcium-phosphate precipitates in the mitochondrial matrix, and thereby buffering calcium levels in the mitochondrial matrix (By similarity). The N-terminal domain can bind calcium and regulates the ATP carrier activity of the transmembrane domain. The apo form of the N-terminal domain is intrinsically disordered and binds to the transmembrane domain, leading to inhibition of the ATP carrier activity. Calcium binding leads to a major conformation change and abolishes the interaction with the transmembrane domain and the inhibition of the ATP carrier activity (By similarity). Belongs to the mitochondrial carrier (TC 2.A.29) family.