Thyrotrophin binding glycoprotein isolated from bovine thyroid.

A butanol-water extraction of bovine thyroid plasma membranes was used to solubilize a thyrotrophin receptor. This method was found to solubilize approximately 12% of membrane proteins and 40% of the binding capacity of thyroid membranes for [125I]TSH. Thyrotrophin binding proteins were further purified 10 times over the butanol-water extract and 70 times over the plasma membranes by means of chromatography on DEAE-cellulose and AcA-54 Ultrogel columns. Purified fractions were found to be glycoproteins containing galactose, mannose, galactosamine, glucosamine and sialic acid. A minute amount (6.0 micrograms per sample) of two glycoprotein fractions obtained after chromatography on AcA-54 Ultrogel caused about 50% inhibition of [125I]TSH binding to thyroid plasma membranes. This inhibition was due to specific interaction between thyrotrophin and isolated glycoproteins.