title: Cholera toxin interactions with thyrotropin receptors on thyroid plasma membranes.
abstract: Unlabeled cholera toxin inhibits [125I]thyrotropin binding to thyrotropin receptors on thyroid plasma membranes. Maximal inhibition by cholera toxin does not exceed 40%, whereas unalbeled thyrotropin completely inhibits [125I]thyrotropin binding to these same membranes. Kinetic analyses of the binding data are compatible with the view that the cholera toxin decreases the number of receptor sites available to thyrotropin and that the mechanism by which the cholera toxin inhibits [125I]thyrotropin binding to these receptor sites involves both competitive and noncompetitive elements.
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D001667:Binding, Competitive; D002417:Cattle; D002462:Cell Membrane / Q000201:enzymology / Q000378:metabolism; D002771:Cholera; D005732:Gangliosides / Q000378:metabolism / Q000494:pharmacology; D007700:Kinetics; D011487:Protein Conformation / Q000187:drug effects; D011956:Receptors, Cell Surface; D013961:Thyroid Gland / Q000378:metabolism* / Q000648:ultrastructure; D013972:Thyrotropin / Q000378:metabolism*; D014118:Toxins, Biological / Q000378:metabolism*
chemical_list: D005732:Gangliosides; D011956:Receptors, Cell Surface; D014118:Toxins, Biological; D013972:Thyrotropin; D000262:Adenylyl Cyclases