Spider venoms are a rich source of ion channel modulators that are increasingly being used as pharmacological tools and as leads for the development of novel therapeutics.1 Almost without exception, these toxins are allosteric modulators (“gating modifiers”) that bind to the voltage-sensor domain of the channel in order to alter channel activation or inactivation.2 Remarkably, despite this ubiquitous mode of action, we know virtually nothing about the molecular basis of the interaction between spider-venom peptides and the voltage-sensor domain of voltage-gated ion channels.
In this study, we used the interaction between the spider-venom peptide VSTx1 and the voltage-sensor domain (VSD) of the KvAP potassium channel as a model system for understanding what drives this type of toxin-channel interaction.
Isotopically labeled VSTx1 and KvAP VSD were produced recombinantly in Escherichia coli. The structure of VSTx1 was solved using triple resonance NMR experiments. KvAP VSD was isotopically labeled for NMR studies and purified in detergent micelles. NMR chemical shift mapping with isotopically KvAP VSD and unlabeled toxin, or vice versa, was then used to probe the molecular details of the interaction.
In future studies, we plan to apply the methods that we have developed here to study the interaction between spider-venom peptides and the voltage-sensor domain of the voltage-gated sodium channel NaV1.7, which is an important target for the development of novel analgesics.