Characterization of nontransformed and transformed androgen receptor from rat submandibular gland

Abstract

Rat submandibular gland cytosol contained androgen receptor which had a single class of specific binding and an apparent dissociation constant of (1.1–1.2) · 10 −9 M. The process of transformation was investigated by a slightly modified minicolumn method in which the transformed receptor complexes were separated from the nontransformed receptor and meroreceptor. 10 mM ATP or pyrophosphate at 0°C induced transformation of androgen receptor as did heat or salt treatment. 20 mM of sodium molybdate completely inhibited transformation that resulted from ATP, heat or salt treatment. The nontransformed androgen receptor complexes sedimented at 8 S and eluted at 250–260 mM KCl from DEAE-Sephacel, and its molecular weight was found to be 220 000 on Sephacryl S300 gel chromatography. On the other hand, the transformed androgen receptor complexes sedimented at 4.1–4.3 S (ATP or KCl treatment) or 3.5–3.8 S (heat treatment) and eluted at 60–80 mM KCl from DEAE-Sephacel. The molecular weight of the transformed androgen receptor complexes was 80 000–85 000 (ATP or KCL treatment) or 70 000–80 000 (heat treatment). These results suggest that the transformation of androgen-receptor complexes from rat submandibular gland was induced by subunit dissociation and that salt bridges may be involved in the subunit interaction.