Figure 4.

Substitution of Thr at the 252 equivalent position of Kv1.2 into use-dependent activation insensitive channels. Use-dependent activation of indicated mutants of Kv1.1, 1.3, and 1.4 (ΔN19 background to eliminate N-type inactivation), was measured using repetitive 10 ms depolarizations (20 Hz) from −80 mV to +60 mV, as described in previous Figures. In each of these channels a Thr (present in the Kv1.2 S2-S3 linker at position Thr252) was substituted at the equivalent position, and mutant channels were expressed in ltk- fibroblasts. Kv1.2 Thr252 is necessary for use-dependent activation, however introduction of this residue in either Kv1.1, Kv1.3, or Kv1.4 was not sufficient to transfer this use-dependent property (n = 14–20 for each construct).