Structure of a Double-Knot Tarantula Toxin Bound to the TRPV1 Channel at the Protein-Lipid Interface

Venom toxins are invaluable tools for exploring the structure and mechanisms of ion channel proteins. Although representative structures of toxin-channel complexes have been solved for toxins that bind from solution, none are available for toxins that bind within the lipid membrane. Here we solve the structure of the bivalent double-knot toxin (DkTx) from tarantula venom, develop improved atomic models of the TRPV1 channel with and without DkTx bound, and investigate the interactions of the toxin with the channel and membrane. Our results demonstrate that DkTx binds to the periphery of the external pore of TRPV1 in a counterclockwise configuration, using a limited toxin-channel interface, while inserting hydrophobic residues into the surrounding membrane to stabilize the complex. In addition, we find that DkTx maximizes the utility of bivalency by optimizing one knot for membrane partitioning and another for channel activation.