title: Ligand-induced change in sedimentation behavior of human progestin receptors.
abstract: We determined the effect of ligand binding on the sedimentation behavior of cytosolic progestin receptors in human uterine leiomyomata, normal endometria and myometria. When cytosols were prelabeled with the tritiated progestin R5020, 4.4S and 7-8S receptors were demonstrated in all three uterine tissues; with postlabeling of fractionated gradients, 4.4S and 9-10S receptors were present. Sodium molybdate (20 mM) blocked the ligand-induced conversion of 9-10S to 7-8S receptors. The relative amount of 7-8S receptor increased with increasing amounts of ligand and time of incubation with ligand (up to 5 hrs); the amount of 9-10S receptor decreased with time. These data indicate that ligand binding to human uterine progestin receptors induces a change from a 9-10S to 7-8S form of receptor. Since molybdate blocks transformation of receptors and the ligand effect on receptor sedimentation, ligand binding to 9-10S receptor and the consequent conversion to 7-8S receptor may be a step preceding transformation of progestin receptors.
mesh_terms: D002499:Centrifugation, Density Gradient; D055598:Chemical Phenomena; D002621:Chemistry; D003600:Cytosol / Q000378:metabolism; D017886:Durapatite; D004717:Endometrium / Q000378:metabolism; D005260:Female; D006801:Humans; D006882:Hydroxyapatites; D007889:Leiomyoma / Q000378:metabolism; D008024:Ligands; D009215:Myometrium / Q000378:metabolism; D011397:Promegestone / Q000378:metabolism; D011479:Protamines; D011980:Receptors, Progesterone / Q000187:drug effects / Q000378:metabolism*; D014594:Uterine Neoplasms / Q000378:metabolism
chemical_list: D006882:Hydroxyapatites; D008024:Ligands; D011479:Protamines; D011980:Receptors, Progesterone; D017886:Durapatite; D011397:Promegestone