Effect of deglycosylation on the structure and hormone-binding activity of the lutropin receptor.
Affinity-purified rat ovarian lutropin (LH) receptor is a single 90 kDa polypeptide which binds to immobilized lectins, indicating that the receptor is a glycoprotein [Keinänen, Kellokumpu, Metsikkö & Rajaniemi (1987) J. Biol. Chem. 262, 7920-7926]. In the present study the glycoprotein nature of the rat ovarian LH receptor was investigated in order to determine the contribution of the glycan moiety to receptor's size and hormone-binding properties. Treatment of the 125I-labelled purified LH receptor with neuraminidase and peptide N-glycosidase F resulted in a decrease in size of LH receptor from 90 kDa to 79 kDa and 62 kDa respectively, as assessed by SDS/polyacrylamide-gel electrophoresis. Endo-alpha-N-acetylgalactosaminidase treatment did not affect the electrophoretic mobility of the intact or neuraminidase-treated LH receptor. Subjecting the membrane-bound LH receptor to similar enzymic treatments followed by ligand blotting showed that the 79 kDa and 62 kDa forms are capable of specific hormone binding. Furthermore, intact and peptide N-glycosidase F-treated membranes bound 125I-labelled human choriogonadotropin with similar affinities. These data suggest that molecular mass of the polypeptide backbone of the LH receptor is 62 kDa. The receptor contains N-glycosidically linked oligosaccharide chains with terminal sialic acid residues, with little or no O-linked oligosaccharide. N-Linked carbohydrate is not required for specific high-affinity hormone binding.
Keinänen
K P
KP
Department of Anatomy, University of Oulu, Finland.
D000581:Amidohydrolases; D000818:Animals; D006063:Chorionic Gonadotropin / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D006026:Glycoside Hydrolases; D006596:Hexosaminidases; D008970:Molecular Weight; D009439:Neuraminidase; D043524:Peptide-N4-(N-acetyl-beta-glucosaminyl) Asparagine Amidase; D051381:Rats; D011974:Receptors, LH / Q000302:isolation & purification / Q000378:metabolism*; D048809:alpha-N-Acetylgalactosaminidase
D006063:Chorionic Gonadotropin; D011974:Receptors, LH; D006026:Glycoside Hydrolases; D006596:Hexosaminidases; D009439:Neuraminidase; C482722:NAGA protein, human; D048809:alpha-N-Acetylgalactosaminidase; D000581:Amidohydrolases; D043524:Peptide-N4-(N-acetyl-beta-glucosaminyl) Asparagine Amidase