Figure 5. Determination of coordinating residues for metal bridges at V343 and S345.

(a) Superimposed scaled current traces demonstrate that three Cys are needed at position V343 for stable Cd²⁺ coordination. The concatamer with Cys mutations at V343 in only one or two of the three subunits is not sensitive to 2 μM of CdCl₂. (b) Superimposed scaled current traces demonstrate that H33 is not required for tight Cd²⁺ bridge formation at residue V343. (c) Superimposed scaled current traces show that two Cys are sufficient for stable Cd²⁺ coordination at residue S345. (d) Superimposed scaled current traces demonstrate that H33 is involved in tight Cd²⁺ coordination at residue S345.