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

(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 Nav. 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 NavRh (PDB ID 4DXW) [7]. (C) Side-view of the same structure in (B). (D) Schematic illustration comparing the structure of eukaryotic and prokaryotic Navs. 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.