Fig. 1: The isolated human TRPV1 S1–S4 domain is folded in a biologically relevant state and binds capsaicin at elevated temperatures.

a Highlighted in red is the hV1-S1S4 construct shown in the rTRPV1 cryo-EM structure (PDB ID: 3J5P) and used throughout our studies. b Cryo-EM determined secondary structure information of rTRPV1 (cyan/purple) compared with the NMR-determined secondary structure (red) from hV1-S1S4 at 45 °C identifies the similarities and differences in secondary structure. The S4 3₁₀ helix is shown in purple. The unassigned region is blocked with opaque white boxes. c Deuterium/hydrogen (D/H) exchange factors show the hV1-S1S4 solvent accessibility is consistent with the anticipated membrane topology. As annotated in (b), unassigned residues are covered with opaque white boxes. Darker gray box represents the average value of exchange factors. Error bars represent per-residue fitting error. d Superimposed ¹H-¹⁵N HSQC spectra of the hV1-S1S4 titration with capsaicin at 37 °C. e Canonical capsaicin binding residues include Y511, S512, T550, and A546, which show saturating binding isotherms as a function of capsaicin. Source data are provided as a Source Data file.