title: Thyroxine-binding globulin: specificity for the hormonally active conformation of triiodothyronine.
abstract: The conformational requirements for binding of triiodothyronine to thyroxine-binding globulin were investigated with triiodothyronine analogs having restricted rotation at the ether bond. Although it has been reported that the predominant conformation of triiodothyronine carries the 3' iodine in a position proximal to the phenylalanine ring, the analog for the distal, hormonally active orientation of the 3' iodine is more effective in displacing triiodothyronine and thyroxine from thyroxine-binding globulin. The lower binding affinity of thyroxine-binding globulin for triiodothyronine as compared to thyroxine may be explained by specificity of the binding site for the less abundant conformation of triiodothyronine.
mesh_terms: D006801:Humans; D007456:Iodine Isotopes; D011485:Protein Binding; D011487:Protein Conformation; D012712:Serum Globulins; D013975:Thyroxine-Binding Proteins; D014284:Triiodothyronine / Q000378:metabolism
chemical_list: D007456:Iodine Isotopes; D012712:Serum Globulins; D013975:Thyroxine-Binding Proteins; D014284:Triiodothyronine