Location of the G375 residue in the context of the BK channel structure. (A and B) Ribbon representation of the full-length structure of a human BK channel (PDB accession no. 6V3G) viewed from the side (A) and down the pore (B) from the extracellular side of the channel. In A, only transmembrane domains from two opposing subunits are shown for clarity, while the cytosolic domains reflect the RCK-containing C-terminal domains from the other two opposing subunits. In B, all four subunits are shown to highlight the tetrameric symmetry in the channel. The transmembrane segments forming VSD and PD are shown in light and dark grey, respectively. RCK1 and RCK2 domains are shown in light and dark blue, respectively. The glycine residue at the position 375 in human BK channels (corresponding to G310 in the BK channel structure determined for a transcript that was missing the first 65 amino acids, and G310 in the frequently used mouse BK channels) is shown in red spheres for each of the subunits.