The strong hydrophobic domain of the activated estrogen receptor of porcine uterus.

Basic estrogen receptor (ER) molecule (vero-ER) of porcine uterus, which was previously shown to be the activated ER necessary to translocate from the cytoplasm into the nucleus, possesses a strongly hydrophobic nature. The strong hydrophobicity of vero-ER was concealed through binding with ER-binding factors (ERBFs). Vero-ER lost its strong hydrophobicity and its capability to bind with ERBFs after limited proteolysis by endogenous protease. The strong hydrophobic domain of vero-ER, indispensable for the nuclear translocation, was assumed to be located near the binding site with ERBFs.