Progesterone Receptor System of Hen Oviduct

Abstract

The cytoplasmic progesterone receptor (PR) system of hen oviduct was shown to be similar to the cytoplasmic estrogen receptor (ER) system of cow uterus described previously. A molecule (sedimentation coefficient, 4.5S; Stokes radius, 45 A; molecular weight, 84,000) designated as native “4S” PR was the sole native component which bound specifically with progesterone. Native “4S” PR was easily modified by a cytoplasmic enzyme to give a partially proteolyzed PR (sedimentation coefficient, 4.5S; Stokes radius, 34 A; molecular weight, 63,000) designated as modified “4S” PR. Modified “4S” PR dissociated in the presence of 0.4 M NaSCN to give a fragment (sedimentation coefficient, 2.9S; Stokes radius, 22 A; molecular weight, 26,000), which reassociated into modified “4S” PR when NaSCN was removed. The presence of a cytoplasmic protein component (Stokes radius, 50A; molecular weight, 140,000) designated as “8S” PR-forming factor [(“08S” PR)-FF], which specifically binds with native “4S” PR to form “8S” PR (sedimentation coefficient of 8.OS) was indicated. (“SS” PR)-FF was dissociated in the presence of 0.4 M KCI into subunits designated as com ponent A (Stokes radius, 36 A; molecular weight, 56,000) and component B (Stokes radius, 17.5 A; molecular weight, 13,000). Component A bound with native “4S” PR to give “5S” PR (sedimentation coefficient, 5.3S), and was further designated as “5S” PR-forming factor [ PR)-FFJ. Component B formed a hexamer (Stokes radius, 46 A; molecular weight, 78,000) under hypotonic (low salt) conditions, which bound with native “4S”PR to give “6S” PR (sedimentation coefficient, 6.3S). The hexamer of component B was designated as “6S” PR-forming factor [“6S”PR)-FF]. (“8S” PR)-FF was estimated to be a 1:1 complex of (“SS” PR)-FF and (“6S” PR)-FF. “4S” PR was dissociated from “8S” PR, “6S” PR, and “5S” PR in hypertonic (0.4 M KCl) buffer. (“5S” PR)-FF, (“6S” PR)-FF, and (“8S” PR)-FF were designated as progesterone receptor binding factors (PRBFs).