Fig. 2. Activity of opioid receptors in the cholesterol-producing strain.

a A protein-based phylogenetic tree of opioid receptors selected to make biosensors. MOR, mu receptor, KOR, kappa receptor, DOR, delta receptor. Dr, D. rerio, zebrafish; Pva, P. vampyrus, flying fox; Mm, M. musculus, mouse; Pb, P. bivittatus, python; Am, A. mexicanus, Mexican tetra; Pvi, P. vitticeps, bearded dragon; Bt, B. taurus, cow. i2, isoform 2. b Activities of agonists and the antagonist naltrexone on opioid receptors were assayed by flow cytometry and mean pEC₅₀ was determined. Agonists clustered by literature receptor-type specificity. n = 3 biologically independent experiments, >2073 cells/condition/replicate. c Biosensor agonist sensitivities (EC₅₀, black circles) relative to sensitivities reported in the literature for mammalian receptors as inhibition constants (Ki, red squares) and EC₅₀/IC₅₀ values (red triangles)^34–45. Fold decrease in sensitivity of the best biosensor relative to the literature average is indicated. Source data are provided as a Source Data file.