Schematic representation of the BLM setup and the structure of prokaryotic Na_v.

(A) The BLM sample chamber and the amplifier. The reference electrode is connected to the trans chamber through a salt bridge and the command electrode is connected to the cis chamber. (B) Top-view of the structure of a full-length prokaryotic Na_v. The four monomers, highlighted in different colors, assemble along each other to form the ionic conducting pore in the center of the tetrameric structure. Picture is generated based on the X-ray crystal structure of Na_vRh (PDB ID 4DXW) [7]. (C) Side-view of the same structure in (B). (D) Schematic illustration comparing the structure of eukaryotic and prokaryotic Na_vs. The four arginine residues on S4 that are responsible for the voltage sensing are denoted by “+” signs. N and C denote the N- and C- termini, respectively.