The Molecular Basis of the Interaction between Spider Toxins and the Voltage-Sensor Domain of Voltage-Gated Ion Channels — ASN Events
  1. Schedule
  2. Session Five - Poster Session A including Refreshments
  3. The Molecular Basis of the Interaction between Spider Toxins and the Voltage-Sensor Domain of Voltage-Gated Ion Channels

The Molecular Basis of the Interaction between Spider Toxins and the Voltage-Sensor Domain of Voltage-Gated Ion Channels (#138)

Carus Lau 1 , Glenn F King 1 , Mehdi Mobli 2
  1. Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD, Australia
  2. Centre for Advanced Imaging, The University of Queensland, St Lucia, QLD, Australia

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. 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.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.

Electrophysiology studies and alanine scanning mutagenesis have been used to determine the pharmacophores of these peptide inhibitors. However, these studies do not provide sufficient information for rational engineering of more selective ion channel inhibitors. In this study, we used the interaction between the spider-venom peptide VSTx1 and the voltage-sensor domain (VSD) of the archeabacterial voltage-gated potassium channel KvAP as a model system for understanding what drives this type of toxin-channel interaction.

Isotopically labelled VSTx1 and KvAP-VSD were produced recombinantly in Escherichia coli. The structure of VSTx1 was solved using triple resonance heteronuclear NMR experiments. The interaction of the isotope-labelled toxin with model membranes was studied using solution state NMR. KvAP-VSD was triple-labelled for NMR studies and purified in detergent micelles.

NMR chemical shift mapping experiments using isotopically labelled KvAP-VSD and unlabelled toxin, or vice versa, were then used to probe the atomic details of the VSTx1-VSD interaction This information was used to guide site-directed mutagenesis studies that enabled identification of VSTx1 and KvAP residues involved in the peptide-ion channel interaction. These studies provide some of the first atomic resolution information on the interaction of this class of spider toxins with the voltage sensor domain of these membrane-bound ion channels.

Finally, we applied our NMR based approach to identify the pharmacophore of a spider toxin that potently inhibits the human voltage-gated sodium channel Nav1.7, an analgesic drug target. Our results closely agree with extensive mutagenesis results conducted on this family of spider toxins.