FIG. 1.

Phylogenetic tree of 18 representative TRPA1 receptors constructed by applying the NJ method (Saitou and Nei 1987) to the nucleotide sequence of the corresponding genes. The numbers next to the different nodes indicate clustering percentage supports generated by 1,000 bootstrap analysis. Relevant branches are lettered (a–f) so that they can be referenced in the text. Three amino acids in TRPA1 that are suspected to enable infrared detection are boxed. The numerical column headings specify the amino acid positions of the rattlesnake TRPA1.