Figure 2.
(A) Concept of the single-turnover K+ exchange experiment to determine electrical events associates with K+ relocation and/or binding. (B) Outward current induced by external K+ application (grey bar), due to negative charge of the reorienting binding site(s). (C-D) Iso-potential planes for hypothesized outward-facing and inward-facing structures. The protein is shown in blue (slice at the depth of the substrate binding site in the left subunit). Conserved, potentially charged residues are overlaid. D454 is omitted due to the possibility of its side chain being neutral. The figure is adapted from [72].