Fig. 2: Temperature-dependent two-state behavior and thermodynamic analysis of hTRPV1 and hV1-S1S4.

a Whole-cell patch-clamp electrophysiology measurements from full-length human TRPV1 in HEK293 cells. b Temperature ramp of hV1-S1S4 monitored by far-UV circular dichroism shows two-state behavior. c The first moment of intrinsic tryptophan fluorescence of hV1-S1S4 as a function of temperature shows two-state transition similar to that identified by CD. d Representative NMR resonance (peak) intensity, G548 in the S4 helix, shows two-state behavior. G548 was chosen due to its similarity to the mean ΔH obtained from NMR. e A histogram of 71 enthalpies from NMR resonance (peak) intensities are shown in red with individual data points shown above as black circles. These data fit to a Gaussian function (black line) provide an average value of 21.2 ± 0.1 kcal mol⁻¹. f Comparison of ΔH values, the first two dark red bars are from the cellular electrophysiology measurements for full-length hTRPV1 from steady-state currents (a) and temperature ramps. A calculated value for one quarter of the steady-state value is also shown. The ΔH values from CD, fluorescence, and NMR are shown in red. g The left panel shows the full-length TRPV1 used for electrophysiology measurements. The middle panel shows the relative size of a TRPV1 monomer. The right panel shows the hV1-S1S4 domain in red, which has similar ΔH as the monomer, showing the relative significance of the hV1-S1S4 in thermosensitivity. The mid-point of the temperature dependence, T₅₀, for the resulting electrophysiology (a), CD (b), fluorescence (c), and NMR (d, e) are 38.1 ± 0.3, 36 ± 1, 38 ± 2, and 40.7 ± 0.6 °C respectively. Errors represent s.e.m. and source data are provided as a Source Data file.