Amino acid residue composition of Adrenergic, Amine, Odorant and Trace amine-associated receptors.

(A) Amino acid percentages for Adrenergic, Amine, Odorant (ORs) and Trace amine-associated Receptors (TAARs). ORs and TAARs profiles differ from Adrenergic and Amine receptors. (B) Amino acid differences for ORs and TAARs expressed as percentage difference from Amine receptors. Many residues show an increase in proportion (positive percentage) and decrease in proportion (negative percentage). Three residues for ORs show a large, 60% difference (methionine-M, histidine-H and tryptophan-W). These three residues also show large differences from TAARs with methionine and histidine comprising the bulk of the statistical difference between them. Results did not change if TAARs and Adrenergic receptors were removed from the Amine receptor superfamily. Amino acids are ordered according to their hydropathy index from 4.5 to -4.5 (L to R). It appears that most of the residue differences favor ORs and TAARs to be more hydrophobic.