Partial purification and properties of the TSH receptors from human thyroid plasma membranes

Human thyroid plasma membranes were solubilized with 0.5% Triton X-100 and TSH receptors were purified by using DEAE-Sephadex, Con A and TSH affinity chromatography. A TSH binding activity was bound to DEAE-Sephadex equilibrated with 0.05 M sodium acetate, pH 6.3, 0.2% Triton X-100 and was eluted by a linear gradient of 0.1 M to 1.0 M ammonium acetate, pH 6.3. Eighty-five percent of the activity was absorbed to Con A Sepharose and was eluted with 0.5 M alpha-methyl-D-mannoside, 0.05 M sodium acetate, pH 6.0. Seventy-five per cent of the TSH binding capacity could be absorbed to TSH-affinity column and was eluted with 0.1 M glycine-HCl, pH 3.0. By sequential application of the above procedures, more than 100-fold purification of the receptor activity was attainable. [125I]TSH binding of this fraction was inhibited by addition of unlabelled TSH in a dose-dependent manner. Scatchard analysis gave a curvilinear plot with a high affinity association constant of 0.72 X 10(9)M-1. By using Ultrogel AcA 34 gel filtration, the molecular size of the hormonereceptor complex was estimated to be 180 000.