PURIFICATION AND CHARACTERIZATION OF THE BOVINE PITUITARY LUTEINIZING-HORMONE-RELEASING HORMONE M(R)60000 BINDING-PROTEIN

Luteinizing hormone releasing hormone (LHRH) regulates the release of luteinizing hormone and follicle stimulating hormone from the pituitar y. This process takes place through interaction with high affinity mem brane receptors. In addition LHRH inhibits the growth of several cance r cell lines through the interaction with M(r) 60000 LHRH receptors. H ere we describe the purification to homogeneity of the M(r) 60000 bovi ne pituitary LHRH binding protein in amounts allowing N-terminal seque ncing and peptide mapping. The procedure describes solubilization of l uteinizing hormone releasing hormone receptors from homogenized bovine pituitaries in an active form by using the detergent Triton X-114. Th e receptors were retained in the Triton X-114 phase during temperature -dependent phase separation. Preparative phase separations were perfor med directly on solubilized bovine pituitary extracts. SDS-PAGE of the purified LHRH receptor after LHRH-immobilized affinity chromatography showed the presence of a single band with M(r) 60000. Partial sequenc ing of this band after trypsin digestion of gel pieces revealed unknow n sequences with a possible homology to other receptors including some G-protein coupled receptors.