A DNA-binding fraction of mouse kidney 3-ketosteroid reductase: comparison with androgen receptors.

Since approximately 1% of 3-ketosteroid reductase (which metabolizes dihydrotestosterone (17 beta-hydroxyl-5 alpha-androstan-3-one] to 5 alpha-androstane-3 alpha, 17 beta-diol or 5 alpha-androstane-3 beta, 17 beta-diol) from mouse kidney cytosol adheres to DNA under conditions that allow virtually complete androgen receptor binding, these two DNA-binding activities were compared in cytosol extracts of mouse kidney and hypothalamus-preoptic area. This DNA-binding fractions of 3-ketosteroid reductase was distinguished from androgen receptor in several ways: (1) its pattern of elution from DNA-cellulose with steps of increasing NaCl concentration differed from that for receptors from wild-type kidney; (2) it was influenced differently by the mutation Tfm, both in level and in DNA-cellulose elution pattern; (3) in mouse kidney cytosol it was relatively stable at moderate (25 degrees C) temperatures which rapidly inactivated ligand-free androgen receptors in the same cytosols; (4) the DNA-binding was not proportional to androgen receptor levels between two wild-type tissues, the hypothalamus-preoptic area and kidney. By these criteria, a simple relationship of androgen receptors and a DNA-binding fraction of 3-ketosteroid reductase activity is unlikely.