Extended Data Figure 1: A minimal TRPV1 channel that is functional and biochemically stable.

a, Mammalian (HEK293) cells expressing a minimal construct (with an N-terminal green fluorescent protein (GFP) tag) responded to various TRPV1 agonists, including capsaicin (Cap; 0.5 μM), extracellular protons (pH 5.0) and double-knot spider toxin (DkTx; 2 μM). Electrophysiological responses were measured in whole-cell patch-clamp configuration. b, c, Dose–responsive curves for capsaicin (b) or protons (c) were determined for minimal (black) or full-length (red) TRPV1, both of which contained an N-terminal GFP fusion. Values were normalized to maximal currents evoked by 30 μM capsaicin (b) or pH 4.0 (c) (n = 6 independent whole-cell recordings). d, DkTx dose–response curves for minimal (black) or full-length (red) TRPV1 as in b and c, determined by calcium imaging. Values were normalized to maximal capsaicin (10 μM)-evoked response in transfected HEK293 cells (n > 30 per point). e, Thermal response profiles for minimal (black) or full-length (red) TRPV1-expressing oocytes reveal similar heat sensitivity. f, Ion permeability ratios of agonist-evoked currents from minimal TRPV1 were estimated from reversal potential shifts in whole-cell patch-clamp recordings of transfected HEK293 cells, revealing no significant differences from full-length channel. g, Gel-filtration profile (Superdex-200) of detergent solubilized TRPV1 after purification on amylose affinity resin and proteolytic removal of maltose-binding protein (MBP) tag. The major species elutes as a symmetrical peak after the void volume (V₀). Inset shows that peak material migrates as a single, homogeneous band on SDS–PAGE (4–12% gradient gel; Coomassie stain).