Schematics of Markov model for Ig of WT hERG1 channels in the presence of extracellular Cd²⁺. The model extends the description of Ig in Fig. 13 A with states and transitions describing the movement of Cd²⁺. States S₀ to S₁₄ (green) describe hERG1 configurations with Cd²⁺ bound to a site in the VSD. States S₁₅ to S₂₄ (blue), and S₂₅ to S₃₀ (brown), are associated with hERG1 configurations having one and two Cd²⁺ ions moved in the VSD, respectively.