Figure 8.

Families of WT, T623A, F627Y, and S641A hERG K⁺ currents recorded in the presence of 5 mM K⁺ _o (left) or in the absence of K⁺ _o (NMG⁺ as substitute, right). The pipette solution contained 135 mM K⁺. In both panels, the voltage protocols are shown at the top and the current–voltage relationships are shown at the bottom. Changing external K⁺ from 5 mM to 0 significantly reduced the WT hERG current (note the different bar scales in WT current traces in 0 and 5 mM K⁺). In both 5 mM and 0 K⁺ _o conditions, no significant current could be recorded in the T623A, F627Y, and S641A mutant hERG channels (n = 4–7 cells).