Protein-Lipid Interfaces Drive DkTx-Mediated TRPV1 Channel Activation

Abstract

A recent cryo-EM structure and a molecular model of the TRPV1 ion channel in complex with its potent agonist, the double knot toxin (DkTx), have provided valuable information on the membrane lipid-binding sites of this complex.To interrogate the functional significance of these protein-lipid interfaces and to compare them with that of lipid-devoid DkTx-TRPV1 interfaces, we generated a series of DkTx variants and characterized their TRPV1-activating properties electrophysiologically. The results of these experiments together with those from our membrane partitioning experiments demonstrate that these structurally extremely similar toxin-lipid interfaces play dominant yet non-overlapping roles in channel activation. The lipid interfaces formed by one of the knots of toxin were observed to confer the toxin with its strong membrane partitioning ability resulting in its slow dissociation from the complex. In contrast, the lipid interfaces formed by the other knot was found to contribute minimally to toxin dissociation rates yet profoundly to the toxin's TRPV1-activating potency. These studies demonstrate that protein-lipid interfaces can play key roles in the function of membrane embedded protein-protein complexes.