(A) Cartoon depiction indicates the location of positions 3.32 and 5.42 in GPCRs. (B) Bioinformatic analysis reveals the number of receptors with anions at positions 3.32 (X) or 5.42 (Y) across various biogenic receptor subfamilies in mouse, as well as TAARs in mouse, rat, humans, and zebrafish. Two mouse, rat, and human TAARs have Asp5.43 instead of Asp5.42, and these are included in columns marked Y = Asp (*). (C) Phylogenetic analysis of the TAAR family in zebrafish (solid lines), mice (dashed lines), rats (dashed lines), and humans (dashed lines); scale bar = 0.5 substitutions per site. TAARs containing only Asp3.32 (blue), only Asp5.42 (red), or both Asp3.32 and Asp5.42 (green) are depicted. Mammalian TAARs with Asp3.32 and Asp5.43 instead of Asp5.42 are green. Glu3.32-containing rodent TAARs and the one zebrafish TAAR, TAAR19f, that lacks both Asp3.32 and Asp5.42 are depicted in black.