Cloning of the LH/CG receptor implications for a unique G-protein coupled receptor.

The proteins encoded by the rat and porcine luteinizing hormone (LH)lchorionic gonadotropin (CG) receptor cDNAs appear to be unique members of the G -protein-coupled receptor family. Although they have the characteristic seven transmembrane domains, the LH/CG receptors have relatively low homology to other members o f this family, do not have a G-protein-coupling domain corresponding to that of the a-adrenergic receptor, and contain an unusual long extracellular domain. Experience in the molecular dissection of this receptor family will help guide investigation of the LHICG receptor's functional domains. Further studies are needed to clarify the origin and significance of the various mRNA species hybridizing on Northern blot analyses. Finally, the rat and porcine receptor cDNAs should permit cloning of the human LH/CG receptor, as well as cloning of the thyroid-stimulating hormone and follicle-stimulating hormone receptors.