![The SF of NavAb and representative current traces of NavAb N49K, S178TNK, S178ANK, and S178GNKmutants. (A) Schematic diagram of the BacNav subunit. Mammalian Navs comprise four homologous repeats. (B) Side view of NavAb N49K mutant (PDB code 8H9W). (C) Side view of the residues 175–179th constituting the SF of NavAb N49K mutant (PDB code 8H9W). The red dashed lines represent the hydration water-exchange sites through which ions pass, formed by the oxygen atoms of the main and side chains of the SF. (D) Recordings of the whole-cell current responses were obtained using the ramp protocol with the solutions of 150 mM [Li+]out and 150 mM [Na+]in. Background (BG) indicates NavAb N49K mutant without the Ser178 mutation. Currents were generated by the step pulse of −20 mV from the −140 mV holding potential, followed by the ramp pulse with different voltage values (shown at the bottom). In this figure and subsequent electrophysiological measurements shown in Figs. 2, 3, and 9, cancellation of the capacitance transients and leak subtraction were performed using a programmed P/10 protocol delivered at −140 mV.](https://cdn.rupress.org/rup/content_public/journal/jgp/158/3/10.1085_jgp.202513855/1/jgp_202513855_fig1.png?Expires=1774746473&Signature=kLf-VRP7rwXWeLVHVguBoseXB9RcERj4A4PEgcFQABpYV9iSD7lqfLqhiybAB5mjm0gqzMXs13f2UniWyOofRlv0gQ98~o2HFvHxGbG46ArjSyfNx~tcM9y0f1yImeMN--qIqEVSnF8fhet2vyFyvI2tIqhKCRQQNhHXCX4F2zUyRF1Yys0v83W~Zym5d5vt1LW07YJX5YOhOv23qOQnqBXOUAp-Vn9NQyVBzLnXLLFRqILRGp4sOoIoAcH0ys2XwN9bxC7dsP1MtknA-C9DUY~rXGrj3BNKV2otDSIzp24Hib490gHN30QfuHqoHTAuZIYPZfIy1q~OygiYg1vNIA__&Key-Pair-Id=APKAIE5G5CRDK6RD3PGA)
The SF of NavAb and representative current traces of NavAb N49K, S178T NK , S178A NK , and S178G NK mutants. (A) Schematic diagram of the BacNav subunit. Mammalian Navs comprise four homologous repeats. (B) Side view of NavAb N49K mutant (PDB code 8H9W). (C) Side view of the residues 175–179th constituting the SF of NavAb N49K mutant (PDB code 8H9W). The red dashed lines represent the hydration water-exchange sites through which ions pass, formed by the oxygen atoms of the main and side chains of the SF. (D) Recordings of the whole-cell current responses were obtained using the ramp protocol with the solutions of 150 mM [Li+]out and 150 mM [Na+]in. Background (BG) indicates NavAb N49K mutant without the Ser178 mutation. Currents were generated by the step pulse of −20 mV from the −140 mV holding potential, followed by the ramp pulse with different voltage values (shown at the bottom). In this figure and subsequent electrophysiological measurements shown in Figs. 2, 3, and 9, cancellation of the capacitance transients and leak subtraction were performed using a programmed P/10 protocol delivered at −140 mV.