Possible binding site of thyrotropin binding inhibitor immunoglobulin (TBII) on the thyrotropin (TSH) receptor, which is different from TSH binding site.
A synthetic decapeptide, P-194, which has the sequence No. 103 to 111 of hTSH receptor structure with an additional N-terminal tyrosine, did not bind TSH nor affected its receptor binding and thyroid stimulating activity. Preincubation of P-194 with sera from thyroid patients caused a significant decrease in TBII activity in almost all 12 TBII positive sera and an increase of thyroid stimulating activity in 3 of 7 Graves' IgG studied. In addition, [125I] P-194 bound to serum IgG fraction from thyroid patients with a positive correlation with TBII (N = 35, r = 0.509, p less than 0.01). The P-194 portion may be, at least a part of, TBII binding site distinct from the TSH binding site on the TSH receptor.
Piraphatdist
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2nd Division of Internal Medicine, Kyoto University, Faculty of Medicine, Japan.
Sugawa
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Inoue
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Enomoto
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Mori
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Imura
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D000818:Animals; D001323:Autoantibodies / Q000378:metabolism*; D001665:Binding Sites; D002462:Cell Membrane / Q000378:metabolism; D006801:Humans; D018828:Immunoglobulins, Thyroid-Stimulating; D007700:Kinetics; D009842:Oligopeptides / Q000138:chemical synthesis; D011989:Receptors, Thyrotropin / Q000276:immunology* / Q000378:metabolism; D013552:Swine; D013959:Thyroid Diseases / Q000276:immunology / Q000378:metabolism; D013961:Thyroid Gland / Q000276:immunology* / Q000378:metabolism; D013972:Thyrotropin / Q000378:metabolism*
D001323:Autoantibodies; D018828:Immunoglobulins, Thyroid-Stimulating; D009842:Oligopeptides; D011989:Receptors, Thyrotropin; D013972:Thyrotropin