Schematic presentation of the effect of voltage (A and C: −; B and D: + at the trans side) and of the side of enrofloxacin addition (A and B: trans; C and D: cis) on the accessibility of the binding site Mini Below (purple in Fig. 5) for enrofloxacin. The blue sphere indicates the presence of (H₂O)₆-Mg²⁺. The cartoons are made for the dominant F+ type insertions (flickering at positive potentials) under the assumption that the location of Mg²⁺ found in crystal structure analysis (Yamashita et al., 2008) also applies to the electrophysiological studies used here.