A ternary complex of Nav1.4 with KIIIA and TTX. (A and B) Side and top views of the complex. TTX (space filled)-binding mode is taken from a previous study (Tikhonov and Zhorov, 2012). KIIIA is shifted toward repeat III, leaving the space for TTX to access its binding site in the narrow part of the outer pore. (C) MCM trajectory of forced TTX egress from its binding site in the presence of KIIIA. Blue dots show the central nitrogen atom of the TTX charged group. (D) TTX system energy along the trajectory (C). The smooth energy profile indicates absence of steric hindrances.