title: Rat ovarian lutropin receptor is a transmembrane protein. Evidence for an Mr-20,000 cytoplasmic domain.
abstract: Membrane topography of the rat ovarian lutropin receptor was studied by two different approaches. Ovarian membrane preparation, labelled with 125I-labelled human choriogonadotropin in vivo, was subjected to extensive chymotryptic digestion. The soluble and membrane-bound radioactive complexes were cross-linked with glutaraldehyde, and analysed by SDS/polyacrylamide-gel electrophoresis and autoradiography. Chymotrypsin solubilized 70-75% of the radioactivity as Mr-96,000, Mr-74,000 and Mr-61,000 complexes, and decreased the size of the membrane-bound 125I-labelled human choriogonadotropin-receptor complex from Mr 130,000 to Mr 110,000. The Mr-110,000 complex was not observed when 0.1% Triton X-100 was present in the proteolytic digestion. Enrichment of inside-out-oriented plasma-membrane vesicles by concanavalin A affinity chromatography increased by 70% the fraction of radioactivity that remained in the membrane fraction after chymotrypsin treatment. Chymotrypsin also diminished the size of the membrane-bound unoccupied receptor from Mr 90,000 to Mr 70,000, as detected by ligand (125I-labelled human choriogonadotropin) blotting. These results suggest that the lutropin receptor is a transmembrane protein with a cytoplasmic domain of Mr 20,000 that is sensitive to proteolytic digestion in the inside-out-oriented plasma-membrane vesicles.
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D002846:Chromatography, Affinity; D002918:Chymotrypsin; D003593:Cytoplasm / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D008024:Ligands; D008565:Membrane Proteins / Q000378:metabolism*; D010053:Ovary / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D011974:Receptors, LH / Q000378:metabolism*
chemical_list: D008024:Ligands; D008565:Membrane Proteins; D011974:Receptors, LH; D002918:Chymotrypsin