Use of concatenated subunits shows that in the open state metal bridges can form between A364C and S472C, possibly within the same subunit. (A) Representative current traces were recorded in the absence (black) or presence (red) of 1 µM Cd²⁺ from inside-out patches expressing one of the tandem dimers (364C472C_364C472C, WT_364C472C, or 364C_472C). Currents were elicited by 500-ms voltage steps to −120 mV from a holding potential of 0 mV, followed by a voltage step to +50 mV. (B) Effects of Cd²⁺ on the average proportions of nondecaying tail current produced by the three tandem–dimeric constructs.