Periods indicate identities and dashes indicate gaps. Functional domains defined for the human AhR (29) are indicated (DNA-binding domains, dark box; ARNT dimerization, underlined; ligand binding, open box; transactivation, vertical box). Sequence alignment was completed using ClustalW (51). GenBank accession numbers for the sequences are as follows: rtAhR2α (AF065137), rtAhR2β (AF065138), and human AhR (S41124).