The membrane-bound 17β-estradiol dehydrogenase of porcine endometrial cells: Purification, characterization and subcellular localization

Abstract

The membrane-bound 17β-estradiol dehydrogenase of porcine endometrial cells was purified to homogeneity as judged by SDS-PAGE and silver staining of a single 32 kD band. A second, more hydrophobic product of the purification protocol contained additional bands at 45 and 80 kD. The 17β-estradiol dehydrogenase activities of both products exceeded those for 17-one reduction by more than 260-fold. Activities of 3α-, 3β- and 20α-dehydrogenases were absent in either fraction. Polyclonal and monoclonal antibodies raised against the 32 kD protein and the more hydrophobic product precipitated the enzymatic activity and reacted with the 32 and 80 kD bands, but not with the 45 kD band in Western blots. The subcellular localization of the enzyme was studied in sections of intact cells and of isolated organelles using gold sol coated with F(ab′) 2 fragments of monoclonal antibody F1. Gold particles were found exclusively over cytoplasmic vesicles of 120–150 nm diameter with electron-dense contents.