Protein Functional Domains
The AhR protein contains several domains critical for function and is classified as a member of the basic helix-loop-helix/Per-Arnt-Sim (bHLH/PAS) family of transcription factors. The bHLH motif is located in the N-terminal of the protein and is a common entity in a variety of transcription factors. Members of the bHLH superfamily have two functionally distinctive and highly conserved domains. The first is the basic-region (b), which is involved in the binding of the transcription factor to DNA. The second is the helix-loop-helix (HLH) region, which facilitates protein-protein interactions. Also contained with the AhR are two PAS domains, PAS-A and PAS-B, which are stretches of 200-350 amino acids that exhibit a high sequence homology to the protein domains that were originally found in the Drosophila genes period (Per) and single-minded (Sim) and in AhR’s dimerization partner the aryl hydrocarbon receptor nuclear translocator (ARNT). The PAS domains support specific secondary interactions with other PAS domain containing proteins, as is the case with AhR and ARNT, so that heterozygous and homozygous protein complexes can form. The ligand binding site of AhR is contained within the PAS-B domain and contains several conserved residues critical for ligand binding. Finally, a Q-rich domain is located in the C-terminal region of the protein and is involved in co-activator recruitment and transactivation.
Read more about this topic: Aryl Hydrocarbon Receptor
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