Progesterone Receptor System of Hen Oviduct

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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).