A model for metalloprotein-catalysed ADP, ATP transport in mitochondria

We propose a hypothetical model for the transmembrane exchange reaction catalysed by the mitochondrial adenine nucleotide carrier protein, which basically consists of an alternating reorientation of a transitory carrier-metal-nucleotide complex. The key features of the model are: the participation of an intrinsic divalent metal ion in the course of transport catalysis; the different stability constants of protonated and deprotonated nucleotide-metal complexes; the exposure and retraction of strategic arginyl residues; the alternating reorientation of the active center involving a change from the cytosolic conformation (Cc) to the matrix conformation (Cm).