Fig. 2.

Current regulation in MthK at its SF. a Structure of the MthK SF, formed by the signature sequence TVGYG, with SF residues shown in sticks and K⁺ ions occupying ion binding sites S1–S4 shown as purple spheres. Two diagonally opposite monomers are shown for clarity. b Outward K⁺ current through MthK at 300 mV as a function of SF opening at T59 forming S4. c, d Comparison of current variations when distance restraints are applied to the ends of TM helices (purple marks, same as in b) or directly to the T59 CA atoms (gray marks), for AMBER and CHARMM force fields, respectively. Error bars represent 95% confidence intervals. Source data are available as a Source Data file.