Figure 2.

The mutation T441S abolishes the allosteric effect of TEA. (A) Allosteric effect of TEA on wild-type ShakerΔ. The time course of C-type inactivation was measured for inward currents at 0 mV with 0 mM [K⁺]_i and 10 mM [K⁺]_o. A half-blocking concentration of internal TEA (0.56 mM) slowed down the inactivation rate 1.7-fold, from 1.5 ± 0.1 s⁻¹ to 0.9 ± 0.1 s⁻¹. For better comparison, the unblocked trace (dotted) is also shown scaled down 2-fold. (B) Inward current with the T441S mutant was 50% blocked by internal application of 9 mM TEA, but there was no effect on the time course of inactivation (1.7 ± 0.2 and 1.8 ± 0.2, with and without 9 mM TEA) because both traces superimpose when scaled to the same amplitude.