1.A.2.2.2
The KirBac3.1 K⁺ channel (a dimer of dimers with gating visualized by atomic force microscopy (Jaroslawski et al., 2007) (regulated by binding lipids, G-proteins, nucleotides, and ions (H⁺, Ca²⁺, and Mg²⁺)). The 3-D structure is available (1XL6_A).  The inhibitory cholesterol binding site has been identified (Fürst et al. 2014). The constricted opening in this, and presumably other, Kir channels does not impede potassium conduction (Black et al. 2020). The structural and dynamic properties of a KirBac3.1 mutant revealed the function of a highly conserved tryptophan in the transmembrane domain (Fagnen et al. 2021).