1. Introduction
Members of the mitochondrial carrier family transport chemically
and structurally diverse compounds across the mitochondrial inner
membrane with a common, yet unresolved, mechanism [1–3]. The
mitochondrial ADP/ATP carrier (AAC), a member of the protein family,
imports ADP into the mitochondrion for conversion to ATP and exports
ATP synthesized by ATP synthase to the cytosol. The transport protein
cycles between a cytoplasmic and matrix state in which the substratebinding
site is accessible to each of these compartments for binding of
ADP and ATP (Fig. 1A) [4]. The specific inhibitors atractyloside and
carboxyatractyloside (CATR) lock the transporter in an aborted
cytoplasmic state, whereas bongkrekic acid (BKA) locks the carrier in
an aborted matrix state [5–9]. These and other observations led to the
formulation of the 'single binding centre gated pore mechanism' for