Structural relationships between the chick oviduct progesterone receptor A and B proteins.
The chick oviduct contains two distinct forms of the progesterone receptor, termed progestophilins A (Mr = 79,000) and B (Mr = 117,000). Although these two hormone-binding proteins differ significantly in physico-chemical characteristics, a good deal of similarity exists between these two molecules. Thus, both proteins display identical hormone-binding kinetics and steroid specificity. The hormone-binding fragments obtained after the action of an endogenous oviduct Ca2+-activated protease are indistinguishable as analyzed by gel filtration chromatography. Both the A and B proteins are capable of binding to DNA-cellulose, although they elute at very different salt concentrations when subjected to gradient elution. In spite of these similarities all attempts to demonstrate the conversion of progestophilin B to A or to show a common precursor to both have been unsuccessful. Therefore, either the A and B receptor proteins are separate products of closely related genes or the conversion of one form to another occurs very rapidly either in vivo or in vitro.
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002645:Chickens; D003600:Cytosol; D004247:DNA / Q000378:metabolism; D004789:Enzyme Activation; D005260:Female; D007700:Kinetics; D008970:Molecular Weight; D010057:Oviducts / Q000378:metabolism*; D010447:Peptide Hydrolases / Q000378:metabolism; D011374:Progesterone / Q000378:metabolism; D011487:Protein Conformation; D011980:Receptors, Progesterone / Q000302:isolation & purification / Q000378:metabolism
D011980:Receptors, Progesterone; D011374:Progesterone; D004247:DNA; D010447:Peptide Hydrolases; D002118:Calcium