title: Calmodulin-stimulated phosphorylation of 17 beta-estradiol receptor on tyrosine.
abstract: The calf uterine 17 beta-estradiol receptor is a phosphoprotein. Phosphorylation-dephosphorylation of the receptor is controlled by a cytosol receptor kinase that activates the hormone binding and by a nuclear phosphatase that inactivates this binding. This report concerns the nature of the 17 beta-estradiol receptor kinase. Highly purified calf uterus 17 beta-estradiol receptor preinactivated by the nuclear phosphatase was used as substrate of the purified receptor kinase. Ca2+ and calmodulin stimulate both the kinase-dependent activation of the hormone binding and 32P incorporation from [gamma-32P]-ATP into the receptor. Maximal stimulation of hormone binding activation requires 1 microM Ca2+ and 0.6 microM calmodulin. Fifteen micromolar trifluoperazine is the lowest concentration that will prevent completely Ca2+-calmodulin stimulation of the kinase. The receptor is phosphorylated by the receptor kinase exclusively on tyrosine. Phosphorylation of proteins on tyrosine is a rare event implicated in hormone-induced cell growth and cell transformation.
mesh_terms: D000818:Animals; D002147:Calmodulin / Q000494:pharmacology*; D002417:Cattle; D002467:Cell Nucleus / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004789:Enzyme Activation; D004958:Estradiol / Q000378:metabolism*; D005260:Female; D007700:Kinetics; D010749:Phosphoprotein Phosphatases / Q000302:isolation & purification / Q000378:metabolism; D010766:Phosphorylation; D010768:Phosphoserine / Q000032:analysis; D010769:Phosphothreonine / Q000032:analysis; D019000:Phosphotyrosine; D011494:Protein Kinases / Q000302:isolation & purification / Q000378:metabolism; D011959:Receptors, Estradiol / Q000302:isolation & purification / Q000378:metabolism*; D011960:Receptors, Estrogen / Q000378:metabolism*; D014443:Tyrosine / Q000031:analogs & derivatives / Q000032:analysis; D014599:Uterus / Q000378:metabolism
chemical_list: D002147:Calmodulin; D011959:Receptors, Estradiol; D011960:Receptors, Estrogen; D010769:Phosphothreonine; D010768:Phosphoserine; D019000:Phosphotyrosine; D014443:Tyrosine; D004958:Estradiol; D011494:Protein Kinases; D010749:Phosphoprotein Phosphatases