NOVEL EFFECTS OF DENDROTOXIN HOMOLOGS ON SUBTYPES OF MAMMALIAN KV1 POTASSIUM CHANNELS EXPRESSED IN XENOPUS OOCYTES

We have examined the effects of tao DTX homologues, toxin T and toxin K, on Kv1.1, Kv1.2 and Kv1.6 channels expressed in Xenopus oocytes. To xin I blocked all three channels; in contrast, toxin K was selective f or Kv1.1. Both toxins slowed channel activation and inactivation kinet ics with 10 nM toxin I approximately doubling activation and inactivat ion time constants of Kv1.1. For the first time, me have demonstrated the selectivity of a DTX homologue for a single cloned Kv1 channel and suggest that these toxins may sterically hinder the conformational ch anges that occur during channel gating.