Toxin K selectively blocks Kv1.1 channels, and both toxins slow channel gating kinetics, suggesting steric hindrance of conformational changes during channel gating.
We have examined the effects of two DTX homologues, toxin I and toxin K, on Kv1.1, Kv1.2 and Kv1.6 channels expressed in Xenopus oocytes. Toxin I blocked all three channels; in contrast, toxin K was selective for Kv1.1. Both toxins slowed channel activation and inactivation kinetics with 10 nM toxin I approximately doubling activation and inactivation time constants of Kv1.1. For the first time, we have demonstrated the selectivity of a DTX homologue for a single cloned Kv1 channel and suggest that these toxins may sterically hinder the conformational changes that occur during channel gating.
Robertson et al. (Mon,) studied this question.