CFTR is the only member of the ABC (ATP-binding cassette) protein superfamily known
to function as an ion channel. Most other ABC proteins are ATP-driven transporters,
in which a cycle of ATP binding and hydrolysis, at intracellular nucleotide binding
domains (NBDs), powers uphill substrate translocation across the membrane. In CFTR,
this same ATP-driven cycle opens and closes a transmembrane pore through which chloride
ions flow rapidly down their electrochemical gradient. Detailed analysis of the pattern
of gating of CFTR channels thus offers the opportunity to learn about mechanisms of
function not only of CFTR channels but also of their ABC transporter ancestors. In
addition, CFTR channel gating is subject to complex regulation by kinase-mediated
phosphorylation at multiple consensus sites in a cytoplasmic regulatory domain that
is unique to CFTR. Here we offer a practical guide to extract useful information about
the mechanisms that control opening and closing of CFTR channels: on how to plan (including
information obtained from analysis of multiple sequence alignments), carry out, and
analyze electrophysiological and biochemical experiments, as well as on how to circumvent
potential pitfalls.
