Metal bridges can form between the S4–S5 linker and C-linker in the open state. Representative current traces of selected single C-linker residue mutants and double mutants with F359C. 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. Currents were recorded in the absence (black) or presence (red) of 1 µM Cd²⁺ from excised inside-out patches expressing the various mutants as indicated. Current traces recorded from the WT partial cysteine-less background, which contains C211Y, C224I, C254V, C266M, C369F, and C373G in addition to the M349I and H462Y mutations, are shown. Current traces recorded from the single F359C mutant are also shown, as well as current traces recorded from single S472C, S473C, S474C, Q476C, R478C, E479C, K482C, and E485C mutants. Current traces from double mutants containing F359C and each of the C-linker mutations are also shown.