Mitochondrial inner membrane carrier protein that mediates the import of NAD(+) into mitochondria (PubMed:16291748, PubMed:32906142, PubMed:33087354). Can transport NAD(+) by unidirectional transport or by exchange with intramitochondrially generated dAMP and dGMP (PubMed:16291748). Also able to transport NAD(+) by exchange with AMP, GMP or deamido-NAD (+) in vitro (PubMed:16291748). dAMP(in) + NAD(+)(out) = dAMP(out) + NAD(+)(in) dGMP(in) + NAD(+)(out) = dGMP(out) + NAD(+)(in) GMP(in) + NAD(+)(out) = GMP(out) + NAD(+)(in) AMP(in) + NAD(+)(out) = AMP(out) + NAD(+)(in) deamido-NAD(+)(in) + NAD(+)(out) = deamido-NAD(+)(out) + NAD(+)(in) Belongs to the mitochondrial carrier (TC 2.A.29) family. Was first identified as the mitochondrial pyruvate transporter (PubMed:12887330). However, later experiments showed that was a NAD(+) transporter (PubMed:16291748).