Structure of ABCB1/P-glycoprotein bound to the CFTR potentiator ivacaftor.

ABCB1 (P-glycoprotein) is an ATP binding cassette transporter that is involved in the clearance of xenobiotics and it affects the disposition of many drugs in the body. Here we have studied ABCB1 in the drug-bound and drug-free states, simultaneously, using high contrast cryo-electron microscopy imaging and a Volta phase plate. The binding of the potent CFTR potentiator, ivacaftor, at a site in the central aqueous cavity is mediated by transmembrane α-helices 3,6,10,11 & 12. Binding is associated with a wider separation of the two halves of the transporter in the inward-facing state. Induced-fit changes the nucleotide binding domains in a way that may explain their increased affinity for ATP when drug is bound. Comparison of ivacaftor-bound structures of CFTR and ABCB1 suggests common features in the binding modes.