A 62 kDa protein functions as estrogen receptor activation factor (E-RAF) in the goat uterus.

Goat uterine estrogen receptor activation factor, a 62 kDa protein existing in three molecular forms, E-RAF I, E-RAF IIA and E-RAF IIB, has been purified to homogeneity. The three forms are immunologically identical, but differ among themselves in their molecular Stokes radii and the sedimentation coefficients. The purified protein combines with the 4 S receptor-estrogen complex of the rat uterine cytosol to produce a 5 S receptor species. The E-RAF IgG cross-reacts with the nuclear 5 S receptor of the rat uterus but not with the cytoplasmic 4 S receptor. The E-RAF competes with the 5 S receptor for the DNA binding sites.