Extended Data Fig. 6: The intracellular domain of state 2.
From: Cryo-EM reveals two distinct serotonin-bound conformations of full-length 5-HT3A receptor
a, A detailed view of the ICD with key residues shown in stick representation. Only two adjacent subunits are shown for clarity. The solvent-accessible vestibule in the ICD calculated using Caver3.047 with a minimum cavity radius of 2.8 Å is shown as dark-cyan spheres. The positively charged residues lining the portal are shown as blue sticks. The negatively charged residues in the vicinity are shown in red-brown. Residues that form the hydrophobic patch at the N-terminal end of the MA helix are shown as green sticks. Residues His309 (post-M3 loop) and Glu250 (M2) are in a potential interaction and are shown in magenta. b, A zoomed view of the ICD to highlight the break in MA–M4 helices (highlighted in magenta) at Gly430. Glycine-mediated transmembrane-helix distortion at the i−3 position is well-studied58, and Gly430 may have a dynamic role at the hinge point between MA and M4 helices. A similar bend in the MA–M4 helix was previously observed in the Torpedo marmorata nAChR structure even in the absence of glycine at the equivalent position3.
