a, A protomer structure of PIEZO2 is presented in a format in which its transmembrane helices roughly adopt a planar configuration. The extracellular loops and intracellular membrane-parallel helices are shown in surface electrostatic potential. Notably, except THU1, which has a short N terminus of seven residues, each of the other eight THUs is preceded by a membrane-parallel helix, which connects perpendicularly to the first transmembrane helices. These intracellular membrane-parallel helices (including TM5pre-α, TM9pre-α, TM13pre-α, TM17pre-α, TM21pre-α, TM25pre-α, TM29pre-α, claspα1–α2 and anchorα3) collectively form an intracellular helical layer with the hydrophobic side facing the membrane side. The enlarged view of the EL7–8, EL11–12, EL15–16, EL19–20 and EL23–24 illustrates the flattened arrangement that is formed by these extracellular loops leaning against each other, except that EL19–20 sits on top of EL23–24. Such an organization might help to stabilize the blade and facilitate conformational propagation from the distal blade to the central region. b, THU5 is used as a typical example to show the organization pattern of the left-handed bundle of four transmembrane helices and the preceding membrane-parallel helix. c, Overlay of THU2 and THU4–THU7 (colour-coded as in a), showing the similar folding pattern. d, Intertwined interaction of the distal beam domain, THU7 and the clasp domain. The residues involved in forming polar interactions are shown in yellow. THU7 is shown in surface representation. The distal part of the beam is apparently kinked at the position of S1466 and buried within a space enclosed by the intracellular side of THU7 and the second and third α-helices of the clasp (claspα2–α3). The clasp domain is composed of two long membrane-parallel helices (claspα1–α2) to form an L-shaped helical structure, and a short helix (claspα3) that is positioned underneath the kink position of the beam. The beam and clasp domains are intertwined together with hydrogen-bond interactions between D1457 and R1702, S1466 and R1717, and R1467 and E1701 for stabilization. The 280 unresolved residues (1728–1947) that link the claspα3 and TM29pre-α1–α2 helices (indicated by the red dashed line) might provide additional interactions and regulation at the distal end of the beam. e, Bottom view of the trimeric central region comprising the beam, the CTD and the latch domain. Two subunits are presented in surface electrostatic potential, and the other subunit is shown in ribbon representation. The proximal end of the beam directly contacts the hairpin-like CTD positioned on top, and connects to the perpendicularly crossed latch domain through 42 unresolved residues (1513–1556). f, Ribbon diagram showing positively charged (blue) and negatively charged (red) residues that contribute to the negative surface potential of the latch domain and positive surface potential of the beam and CTD (as shown in e). The C-terminal section of the latch domain is rich in negatively charged and polar residues (1572-ETDSEE-1577) and is sandwiched in between the beam and the CTD with clusters of positively charged residues (R1500, R1504, K1507 and K1512 in the beam and K2815, R2818 and K2820 in the C-terminal tail). Y1568 in the latch domain points towards the putative intracellular exit of the central pore and forms hydrogen bonds with E2811, which contributes to the cytosolic constriction neck. g, Ribbon diagram showing the intertwined polar interactions of the indicated structural domains. The long membrane-parallel anchorα3 sits right on top of the CTD-hairpin plane and connects to the outer helix through a lysine-rich anchor–outer-helix linker (2456-KRYPQPRGQKKKK-2468), which forms interactions with the polar-residue-rich anchorα2–α3 turn (2426-TDTTT-2430), the glutamate-rich region of the CTDα1–α2-turn (2789-ETGELELEED-2798) and the N-terminal section of the latch domain. Several pairs of hydrogen bonds, including D2427–K2465, T2428–E2796 and T2429–E2797, might help to facilitate the intertwined interactions. The corresponding anchor–outer-helix linker in PIEZO1 is critical for mediating regulation by the sarco/endoplasmic reticulum Ca2+-ATPase (SERCA), which binds to both PIEZO1 and PIEZO2.