Abstract

The hydrophobic character of the receptor for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) has been estimated by its tendency to adsorb to hydrophobically interacting matrices. The receptor is adsorbed to uncharged pentyl-Sepharose but not to butyl-Sepharose at 1 M NaCl. It is also adsorbed to phenyl-Sepharose or Cibacron blue-Sepharose at lower ionic strengths (0-0.15 M NaCl). Elution of adsorbed receptor could not be achieved under mild conditions (decreasing salt concentration, increasing glycerol concentration). A concentration of 0.2% (w/v) of the detergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS) was required to desorb the receptor from pentyl-Sepharose with an approximate yield of 11-14% of the specific [3H]TCDD-binding activity. The CHAPS-treated receptor exhibited the same physicochemical characteristics as that in crude cytosol (4-5 S, Stokes radius approximately 60 A). Furthermore, the effects of detergents other than CHAPS on hydrodynamic parameters and on [3H]TCDD binding to the receptor were studied. In conclusion the TCDD receptor showed more pronounced hydrophobic properties than those reported for steroid hormone receptors.