Structural models and pore dimensions of Cx26 hemichannels. (A) Top view of the Cx26 hemichannel corresponding to the crystal structure (Protein Data Bank accession no. 2ZW3; Maeda et al., 2009). The six protein subunits, depicted in different colors, surround a central aqueous pore. (B) Side view of the structure shown in A, illustrating the TM architecture and channel pore relative to two opposite subunits. The extracellular entrance of the channel (z = 45 Å) is at the top of the structure. (C) Pore radius of the Cx26 “crystal” hemichannel determined by HOLE plotted as a function of the z coordinate. (D) Top view of the “completed” crystal structure including the atomic coordinates of the N-terminal methionine residue (Met1), the side chains of K15, S17, and S19, as well as residues comprising the CL and the C terminus. (E) Side view of the completed crystal structure, showing the same subunits as in B. (F) Pore radius of the completed crystal structure. (G) Top view of the channel conformation that has the smallest RMSD from the average equilibrated structure, average pore dimension, and pore-lining probability. We define this structure as the “average equilibrated structure.” (H) Side view of the average equilibrated structure. (I) Pore dimensions of the average equilibrated structure. The mean pore radius is depicted by the black line. The red lines represent the dynamic variation by plotting the mean ± the standard deviation determined from the four 20-ns production-phase simulations.