A structure for the porcine TSH receptor

Affinity purified, detergent-solubilised porcine TSH receptors have been crosslinked to a 125I-labelled photoactive derivative of TSH and analysed by gel electrophoresis, gel filtration and sucrose density gradient centrifugation. Our studies suggest that the porcine TSH receptor is made up of a hydrophilic A subunit with an Mr about 45000 linked to an amphiphilic B subunit (Mrapprox. 25 000) by a disulphide bridge(s). The A subunit forms the binding site for TSH on the outside of the cell membrane. The B subunit appears to penetrate the membrane and form the site for interaction with adenylate cyclase either in the lipid bilayer or close to the cytoplasmic surface of the membrane.