Fig. 1.

TWIK1 sequence and topological organization. (A) Functional domains in a TWIK1 subunit: transmembrane segments (M1–M4), coiled-coiled self-interacting domain (SID), pore domains (P1 and P2), pore helices (ph), and selectivity filter sequences (purple bold line) are indicated. (B) Sequence alignment in which TWIK1 residues mutated in this article. Residues affecting ion selectivity are in red; residues affecting channel activity are in blue. (C and D) Structural modeling of a TWIK1 dimer. Cytoplasmic and extracellular domains are not depicted. (C) Top view of the TWIK1 extracellular side. (D) Side views of the TWIK1 membrane domain; out-of-plane loops and helices are not depicted. Mutated residues shown in B are depicted.