Detection of the 2,3,7,8-tetpachlorodibenzo-p-dioxin (TCDD) receptor in rat liver by isoelectric focusing in polyacrylamide gels

A stereospecific, high-affinity binding protein (receptor protein) for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in rat liver cytosol can be demonstrated using isoelectric focusing in polyacrylamide gels. In its native form, the receptor protein focuses at a varying pI possibly due to aggregation. However, if limited proteolysis of the receptor is carried out, the trypsinized receptor focuses as a single sharp peak at pI 5.15-5.25. Using this method the receptor can be separated from a serum TCDD-binding protein (pI 5.7-5.8) that is resistant to dextran-coated charcoal (DCC) treatment. The binding of [³H] TCDD to the receptor is competed for by 2,3,7,8-tetrachlorodibenzofuran (TCDBF), 3-methylcholanthrene (MC), and {amalgamation}-naphthoflavone ({amalgamation}NF) but not by phenobarbital (PhB) or pregnenolone-16α-carbonitrile (PCN). The method described can be used for detection and quantitation of the TCDD receptor.