Binding to R 1881 (methyltrienolone) of proteins from human benign prostatic hypertrophy

Cytosol of human benign prostatic hypertrophy bound to R 1881 in a high affinity manner. Most of the protein which bound to R 1881 was recovered in the precipitate of a 0-30% saturation of ammonium sulfate, and was eluted in the void volume on a Sephadex G-200 column. The binding of cytosol to R 1881 was more inhibited by progestins than by dihydrotestosterone and estradiol-17 beta. The binder therefore seemed to be different from dihydrotestosterone-binding protein. The R 1881-binding component extracted from the nuclei by 0.4M KCl bound also to dihydrotestosterone in a high affinity manner. Cytosol prelabeled with R 1881 was bound to the nuclei in a nonsaturable process, and the extraction pattern of R 1881 by 0.4M KCl from the nuclei was almost identical to that in the case of dihydrotestosterone as the ligand. These results suggested that a part of the cytosolic protein which bound to R 1881 entered the nuclei where it bound to nuclear such components as dihydrotestosterone-binding protein.