Molecular determinants of μ-conotoxin KIIIA interaction with the human voltage-gated sodium channel Na_V1.7

The voltage-gated sodium (Na_V) channel subtype Na_V1.7 plays a critical role in pain signaling, making it an important drug target. Here we studied the molecular interactions between micro-Conotoxin KIIIA (KIIIA) and the human Na_V1.7 channel (hNa_V1.7). We developed a structural model of hNa_V1.7 using Rosetta computational modeling and performed in silico docking of KIIIA using RosettaDock to predict residues forming specific pairwise contacts between KIIIA and hNa_V1.7. We experimentally validated these contacts using mutant cycle analysis. Comparison between our KIIIA-hNa_V1.7 model and the cryo-EM structure of KIIIA-hNa_V1.2 revealed key similarities and differences between Na_V channel subtypes with potential implications for the molecular mechanism of toxin block. The accuracy of our integrative approach, combining structural data with computational modeling, experimental validation, and molecular dynamics simulations, suggests that Rosetta structural predictions will be useful for rational design of novel biologics targeting specific Na_V channels.