Identification of amino acid residues in the Ah receptor involved in ligand binding.

The Ah receptor (AhR) is a ligand-activated transcription factor. Five amino acids as candidate amino acids necessary for ligand binding within or near the ligand-binding domain were selected based on their evolutional conservation and their aromatic nature that could interact with xenobiotic ligands. These amino acids were changed to Ala, and the mutated AhRs were subjected to a test of their transactivation activity in HeLa cells.