Science · 1990 · 153 citations · 16 references
Life SciencesEndocrinologyMolecular BiologyHormone BiochemistryReproductive EndocrinologyReproductive PhysiologyGonadal HormonesHormone Binding ProteinsHormone ReceptorsHormone StructurePituitary HormonesThyroid EndocrinologyAmino AcidsGlycoprotein HormonesHormone Receptor Binding DomainsHormone Receptor Binding ProteinsInsertionsLuteinizing Hormone ReceptorsThyroid Hormone Binding ProteinsThyroid Hormone Receptors
Thyrotropin (TSH), luteinizing hormone (LH), and chorionic gonadotropin (CG) are structurally related glycoprotein hormones, which bind to receptors that share a high degree of sequence similarity. However, comparison of the primary amino acid sequences of the TSH and LH-CG receptors reveals two unique insertions of 8 and 50 amino acids in the extracellular domain of the TSH receptor. The functional significance of these insertions were determined by site-directed mutagenesis. Deletion of the 50-amino acid tract (residues 317 to 366) had no effect on TSH binding or on TSH and thyroid-stimulating immunoglobulin (TSI) biological activities. In contrast, either deletion or substitution of the eight-amino acid region (residues 38 to 45) abolished these activities. This eight-amino acid tract near the amino terminus of the TSH receptor appears to be an important site of interaction for both TSH and TSI.
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