ARNT/HIF-1 beta: Proteins and Enzymes

ARNT (Aryl hydrocarbon nuclear translocator; also HIF-1 beta) is an 87 kDa member of the bHLH-PAS subclass of the bHLH family of transcription factors. It is widely expressed, and serves as part of both the NF kappa B and aryl hydrocarbon receptor (AHR) signaling nodes. For the AHR, the AHR is normally inactive and bound to hsp90 in the cytosol. Following ligand binding, the AHR complex enters the nucleus, dissociates from hsp90, dimerizes with ARNT, and then binds response elements of select genes. Human ARNT is 789 amino acids (aa) in length. It contains a DNA-binding region (aa 87-143), two PAS domains (aa 161-235 and 362-458) and one PAC region (aa 424-467). There are multiple potential splice forms. Two alternate start sites are found at Met10 and Met354, there is a deletion of aa 329-755 and 77-91, and an Ala substitution for aa 328-789.