Fig. 2.

Basic architecture of an ABC transporter. Regardless of the direction of the transport, all ABC transporters are composed of a minimum “functional core” formed by two catalytic domains (NBD) and two transmembrane domains (TMDs). The NBDs, TMDs, and ATP molecules are coloured in orange, blue, and green, respectively. This figure represents the cryo-EM structure of the phosphorylated cystic fibrosis transmembrane conductance regulator (CFTR) channel (PDB code: 6O1V) [46]