A helical distortion in the TRP channel pore. (A) Structural alignment of a pore domain subunit of TRPV1 (pink), NavAb (yellow), and the paddle chimera (blue). (Top inset) Y671 of TRPV1 has no aligned residue in NavAb, in effect shifting the register of the helix (at the top of S6, the green and black C-β atoms are aligned, whereas after 671, they are staggered). (Bottom inset) Several pairs corresponding to contacting ECs in TRPV1 (left) are not coupled nor even in contact in the equivalent pairs of the Kv paddle chimera (right). (B; top) The “structural alignment” of TRPV1, NavAb, and the paddle chimera S6 helices, which suggests that TRP 671 is an insert picked up in TRP channels. (Bottom) An “evolutionarily plausible” alignment of TRPV1, NavAb, and the paddle chimera S6 in which the conserved asparagine observed in Nav, Cav, and TRP channels is aligned. (C) Gating motions of TRPV1 as determined by cryoelectron microscopy. On the left, two S6 helices of the apo “closed” TRPV1 pore domain are shown. On the right, the same “open” pore domain helices from the RTX/DkTx-bound TRPV1 structure are shown. Broken hydrogen bonds beneath Y671 reform as the channel shifts from closed to open, but only at the expense of new broken hydrogen bonds above A680, caused by the helical distortion.