Heterogeneity of rat hepatic Ah Receptor: Identification of two receptor forms which differ in their biochemical properties

✍ Scribed by Denison, Michael S.

• Book ID: 102875655
• Publisher: John Wiley and Sons
• Year: 1992
• Tongue: English
• Weight: 893 KB
• Volume: 7
• Category: Article
• ISSN: 0887-2082
• DOI: 10.1002/jbt.2570070408

✦ Synopsis

Abstract

In cytosol, the rat hepatic Ah receptor (AhR) appears to exist in two distinct forms (AhR^α^, AhR^β^) in similar concentration. The binding of ligand (2,3,7,8‐tetrachlorodibenzo‐p‐dioxin (TCDD)) to AhR^α^ requires the receptor be in its oligomeric 8–10 to S conformation (bound to other protein subunits), while ligand binding to AhR^β^ can occur with the dissociated 5–6 S form. Occupancy of AhR^β^ by ligand (TCDD) protects it from salt‐dependent inactivation; AhR^β^ is not inactivated by high salt conditions. The addition of molybdate to cytosol during tissue homogenization stabilized AhR^α^ against salt‐dependent inactivation and subunit dissociation but did not prevent dissociation of AhR^β^ by high salt. Although the presence of molybdate appears to stabilize AhR^α^ in its oligomeric 8–10 S, it had no significant effect on the overall amount of TCDD:AhR complex which bound to its specific DNA recognition site, the dioxin responsive element (DRE). These results suggest that AhR^α^, unlike AhR^β^, is either unable to transform or bind to the DRE with high affinity.