Many proteins form dimers as functional units. One such
example is the Cystic Fibrosis Transmembrane conductance
Regulator (CFTR). CFTR is a chloride channel in the apicalmembrane
of epithelial cells that is regulated by cAMP-dependent protein
kinase (PKA) and ATP[1]. The 1480-amino acid protein belongs to
the superfamily of ATP-binding cassette (ABC) transporters. CFTR
consists of two transmembrane domains (TMDs), two intracellular
nucleotide-binding domains (NBD1 and NBD2) and one unique
intracellular regulatory (R) domain. It has been proposed that the
ATP-driven dimerization of NBD1 andNBD2 leads to the opening of
thechannel, and thesubsequenthydrolysisofATPatNDB2results in
dimerdissociationwhichisresponsiblefor theclosingof thechannel
(for review, see Refs.[2–4]).