Mechanism and site of Cu²⁺ action. (A) Scheme 1 (see text), green indicates Cu²⁺-dependent mechanisms, black represents HA model (Horrigan and Aldrich, 2002). (B and C) Residues mutated in mSlo1 are mapped onto the structure of a Kv1.2/Kv2.1 chimera (Long et al., 2007). B and C show side and top views, respectively. Only the S1–S4 segments from one subunit are shown with S1–S2 linker removed for clarity. Putative Cu²⁺-coordinating residues were changed to the corresponding residue from mSlo1: D133(red), Q151(yellow), D153(red), R207(cyan). The backbone was colored dark blue at other positions that were tested. Dotted spheres indicate the position of water molecules in the structure. The green sphere illustrates a possible position for Cu²⁺.