Schematic representation of the basic structural biology of connexins. a Secondary structure representation of a gap junction channel formed by end-to-end docking of two hemichannels of Cx26, colored in green and blue. Membrane planes depicted by red solid lines. b Representative hemichannel invoving hexameric arrangement of connexin protomers. Protomer domains appear denoted using color-coded names in one protomer as reference. c Intracellular view of a human Cx26 hemichannel in its open conformation with inner pore diameter of 14 Å (see text for explanation on channel openness). d 2D-plot denoting connexin secondary structure and the approximate position of every residue. The 3D coordinates of the human Cx26 gap junction and membrane planes were retrieved from Orientation of Proteins in Membrane Database  (using PDB id: 2ZW3). Panels a to c were rendered using Pymol. Panel d was modified from Nakagawa et al.