The Mechanism of Na+/K+ Selectivity in Mammalian Voltage-Gated Sodium Channels Based on Molecular Dynamics Simulation

Voltage-gated sodium (Na-v) channels and their Na+/K+ selectivity are of great importance in the mammalian neuronal signaling. According to mutational analysis, the Na+/K+ selectivity in mammalian Nav channels is mainly determined by the Lys and Asp/Glu residues located at the constriction site within the selectivity filter. Despite successful molecular dynamics simulations conducted on the prokaryotic Na-v channels, the lack of Lys at the constriction site of prokaryotic Na-v channels limits how much can be learned about the Na+/K+ selectivity in mammalian Na-v channels. In this work, we modeled the mammalian Na-v channel by mutating the key residues at the constriction site in a prokaryotic Na-v channel (NavRh) to its mammalian counterpart. By simulating the mutant structure, we found that the Na+ preference in mammalian Na-v channels is collaboratively achieved by the deselection from Lys and the selection from Asp/Glu within the constriction site.