Assignment of the ligand binding site of the porcine estradiol receptor to the N-terminal 17 kDa part of domain E.

Ligand-filled porcine estradiol receptor was adsorbed to heparin-Sepharose, from which a 26 kDa fragment was released by papain. Its mass was reduced to a 17 kDa fragment by trypsin. The sedimentation velocities of both estradiol binding fragments increased after reaction with the MAB 13H2. The same antibody identified the denatured fragments on Western blots. The N-terminal 21 amino acid sequence was obtained from the 17 kDa peptide which corresponds to amino acids 303-323 of the human receptor with four amino acids exchanged. This indicates that the ligand binding site resides in the N-terminal 17 kDa portion of domain E.