The beta-subunit of human choriogonadotropin interacts with the exodomain of the luteinizing hormone/choriogonadotropin receptor and changes its interaction with the alpha-subunit.
Human CG (hCG) consists of a common alpha-subunit and a hormone-specific beta-subunit. Similarly, its receptor is also composed of two domains, an extracellular N-terminal half (exodomain) and a membrane-associated C-terminal half (endodomain). hCG initially binds the exodomain of the receptor after which the resulting hCG/exodomain complex is thought to interact with the endodomain. This secondary interaction is considered responsible for signal generation. Despite the importance, it is unclear which hormone subunit interacts with the exodomain or the endodomain. As a step to determine the mechanisms of the initial and secondary interactions and signal generation, we investigated the interaction of the hormone-specific beta-subunit in hCG with the receptor's exodomain. A photoactivable hCG derivative consisting of the wild-type alpha-subunit and a photoactivable beta-subunit derivative was prepared and used to label the exodomain. The analysis and immunoprecipitation of photoaffinity labeled exodomain demonstrate that the beta-subunit in hCG makes the direct contact with the exodomain.
Hong
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SH
Department of Molecular Biology, University of Wyoming, Laramie 82071-3944, USA.
Ji
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IH
Ji
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TH
D001345:Autoradiography; D001665:Binding Sites; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000737:chemistry / Q000378:metabolism*; D003432:Cross-Linking Reagents; D003460:Crystallization; D004229:Dithiothreitol; D004591:Electrophoresis, Polyacrylamide Gel; D015292:Glycoprotein Hormones, alpha Subunit / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D007163:Immunosorbent Techniques; D007457:Iodine Radioisotopes; D008958:Models, Molecular; D019920:Photoaffinity Labels; D011974:Receptors, LH / Q000737:chemistry / Q000378:metabolism*; D012995:Solubility; D014466:Ultraviolet Rays
D018997:Chorionic Gonadotropin, beta Subunit, Human; D003432:Cross-Linking Reagents; D015292:Glycoprotein Hormones, alpha Subunit; D007457:Iodine Radioisotopes; D019920:Photoaffinity Labels; D011974:Receptors, LH; D004229:Dithiothreitol