Activation of the chick oviduct progesterone receptor by heparin in the presence or absence of hormone.
Activation (transformation) of the chick oviduct progesterone receptor was found to be induced at 0 degrees C by heparin free in solution as well as by chromatography on a column of heparin linked to acrylamide/agarose. The transformed molecule displayed properties of the activated form of [3H]progesterone-receptor complex obtained by heat treatment or by high ionic strength: smaller size (s20,w = 3.9 S, Stokes radius = 5.2 nm), lower rate of dissociation (t 1/2 approx. 50 h at 0 degrees C compared with approx. 20 h for the 'native' form) and increased binding to phosphocellulose. In all cases, molybdate was an effective inhibitor of transformation and stabilized a large 'native' form (s20,w = 7.9 S, Stokes radius = 7.6 nm). Transformation by neither KCl nor heparin depended on the presence of ligand bound to the receptor, and the properties of the receptor molecule produced by treatment of ligand-free receptor with high ionic strength or with heparin were identical with those of the activated progesterone-receptor complex, demonstrating that receptor activation can be obtained experimentally in the absence of hormone. Our data are compatible with a model in which activation implies separation of the 4 S units, which compose the approx. 8 S 'native' form.
D000818:Animals; D002499:Centrifugation, Density Gradient; D002645:Chickens; D005260:Female; D006493:Heparin / Q000494:pharmacology*; D066298:In Vitro Techniques; D007700:Kinetics; D046911:Macromolecular Substances; D008982:Molybdenum / Q000494:pharmacology; D009994:Osmolar Concentration; D010057:Oviducts / Q000378:metabolism*; D011189:Potassium Chloride / Q000494:pharmacology; D011374:Progesterone / Q000378:metabolism*; D011980:Receptors, Progesterone / Q000187:drug effects / Q000378:metabolism*
D046911:Macromolecular Substances; D011980:Receptors, Progesterone; D011374:Progesterone; D011189:Potassium Chloride; D008982:Molybdenum; D006493:Heparin