Side view of Cx26 (A) and Cx32*43E1 N2E ΔCT (B) hemichannels after equilibration by all atom molecular dynamics in a fully hydrated POPC membrane. The side chains of residues 108 (green balls), 109 (blue balls), and 56 (orange balls) are shown. The backbone of the parahelix (residues 42–51) is depicted by the red ribbon. The C terminus of Cx32 was not included in the homology model. The Cx32*43E1 N2E hemichannel was incorporated into a fully hydrated POPC membrane as described previously (Kwon et al., 2011). A tetragonal periodic boundary box, 103 × 103 × 109 Å including the protein, lipid membrane, TIP3 waters, and 150 mM KCl, was constructed with a program contained in CHARMM-GUI. All protein atoms in this system used the CHARMM 22 force field with CMAP corrections. The CHARMM 36 force field was used for lipid molecules (Feller and MacKerell, 2000). The system was equilibrated for 1 µs at 310 K using NPnT dynamics in Desmond using an Anton computer (Shaw et al., 2007). NPnT is the ensemble name for constant number of particles (N), pressure in normal direction (Pn), and temperature (T).
