Two functional states of human CFTR Two functional states of human CFTR. (A) Schematic diagram showing the domain structure of CFTR. The numbers represent the range of residues visible in the cryo-EM map, not the exact boundaries of different domains. Two functional states of human CFTR. (A) Schematic diagram showing the domain structure of CFTR. The numbers represent the range of residues visible in the cryo-EM map, not the exact boundaries of different domains. (B) Ribbon diagrams of the dephosphorylated, ATP-free conformation (Left; PDB ID code 5UAK) and the phosphorylated, ATP-bound structure (Right). Regions not resolved in the structure are shown as dashed lines. The EM densities, shown in red, correspond to unstructured regions within the R domain. TM 8 is highlighted in cylinder. ATP is shown in ball-and-stick and colored by heteroatom. The distances between the last visible residue in the R domain and the first residue in TMD2 are indicated. Zhe Zhang et al. PNAS doi:10.1073/pnas.1815287115 ©2018 by National Academy of Sciences