The sole member of the TRPA sub-family, TRPA1, contains 14 N-terminal ankyrin repeats and is believed to function as a mechanical stress sensor. It is expressed in the dorsal root ganglion, trigeminal ganglion, and hair cells. The temperature sensitivity of TRPA1 is highly disputed, with some reports claiming that it is activated by noxiously cold stimuli and others disputing such a claim. TRPA1 is known to be activated by compounds capable of forming covalent chemical bonds with the protein's cysteins like isothiocyanates, which are the pungent chemicals in substances such as mustard oil and wasabi and Michael acceptors such as cinnamaldehyde in cinnamon, amongst numerous other substances. Non-covalent activators of TRPA1 also exists, such as methyl salicylate in winter green oil and the synthetic compound PF-4840154.
^Ryckmans T, Aubdool A A, Bodkin J V, Cox P, Brain S D, Dupont T, Fairman E, Hashizume Y, Ishii N, Kato T, Kitching L, Newman J, Omoto K, Rawson D and Strover J (July 2011). "Design and pharmacological evaluation of PF-4840154, a non-electrophilic reference agonist of the TrpA1 channel". Bioorganic. Med. Chem. Lett. (21): 4857–4859. doi:10.1016/j.bmcl.2011.06.035. PMID21741838.