Figure 7. Functional layers and proposed mechanism for channel opening in TMEM175 channels.

(a) Functional layers in the MtTMEM175 pore. Two subunits are shown (right side only partly). Important residues in MtTMEM175 and hTMEM175 and for comparison the pore radius (in Å) are indicated. The ion binding site is shown in red, gate-residues in magenta and residues required for selectivity in blue and cyan. (b) Schematic side view of MtTMEM175 in closed (left) and proposed conductive state (right). Key residues on helix one are shown as spheres. Two subunits are omitted for clarity. K⁺ ions are shown as purple spheres. A clockwise rotation of helix 1 (viewed from intracellular) of 8–15° would widen the pore sufficiently for K⁺ ions to permeate (indicated by curved arrows in the bottom panel).