... SapienzaÕ, Roma, ItalyLigand binding by the aryl hydrocarbon receptor (AhR), a member of the bHLH-PAS family of transcriptional reg-ulatory proteins, has been mapped to a region within the second ... ail: Anna.Tramontano@uniroma1.itAbbreviations: AhR, aryl hydrocarbon receptor; PYP, photoactiveyellow protein; LBD, ligand binding domai n; mAhR, mouse aryl hydrocarbon receptor; PCDD, polychlorinated ... lowerthan mAhR [19]; the AhR-1 ortholog of Caenorhabditiselegans (AhR-1C.E.), neither photoafđnity labeled by a dioxin analog, nor activated by b-naphto¯avone in a yeastsystem [20]; the rainbow...