Voltage-gated ion channels (VGICs) are a superfamily of membrane proteins encoded by more than 143 genes in the human genome, making it one of the largest superfamilies of signal transduction proteins. These ion channels are recognised as among one of the most important, yet underutilised, drug targets. Unsurprisingly, there has been a surge of biophysical studies in the recent decades that aim to develop antagonist modulators such as peptide toxins as therapeutic agents. The sodium VGIC subtype Nav1.7 is involved in nociception, and as such is one of the most promising drug targets for inhibition [1].
Structural studies of membrane proteins are typically undertaken in detergent micelles. Due to the absence of a native lipid bilayer, this model can lead to poor in vitro stability, sample inhomogeneity and does not represent the native environment for a channel [2]. Recently, nanodiscs (NDs) have been developed to solubilize and reconstruct membrane proteins in lipid bilayers. Nanodiscs consist of a membrane scaffold protein wrapped around a lipid bilayer, forming disc-like rafts. NDs can essentially mimic membrane environments, and be ultimately used to derive physiologically relevant functional and structural data [3,4].
We are interested in the application of nanodiscs with NMR spectroscopy in a novel approach to overcome past experimental limitations and advance research on VGICs and their peptide modulators. The elucidation of peptide-channel binding, both the kinetics and structural interaction, is uncommon in VGIC research due to experimental difficulties when using detergent micelles for VGICs. With nanodiscs we can solubilize the channel quantitatively in homogenous and compact models, while also providing a native environment, for biophysical studies such as NMR. Applying these methods, we are studying the spider toxin VSTx1 and the potassium VGIC, KvAP. We will present data on the peptide’s channel specific binding affinity (Kd) and the residue-specific interactions between both.