Subunit interaction of human chorionic gonadotropin (hCG) with rat ovarian luteinizing hormone (LH)/CG receptor

Structural characterization of the carbohydrates of the rat ovarian luteinizing hormone/chorionic gonadotropin receptor

The numbers and types of oligosaccharide present on the rat ovarian luteinizing hormone (LH)/chorionic gonadotropin (CG) receptor were determined by treating radiolabelled purified receptors with glycosidases and examining the changes in electrophoretic mobility and number of radiolabelled bands on SDS/PAGE. The purified receptor was also transferred to nitrocellulose after SDS/PAGE and probed with digoxigenin-labelled lectins. The following conclusions were drawn: (1) the rat ovarian LH/CG receptor contains at least two complex-type N-linked oligosaccharide chains, of which one is biantennary and the rest multiantennary. (2) The N-linked chains terminate in either unsubstituted galactose or sialic acid linked alpha 2-3 or alpha 2-6 to the penultimate galactose. (3) The N-linked oligosaccharides also contain internal poly(N-acetyl-lactosamine) sequences and fucose-linked alpha 1-6 to the proximal N-acetylglucosamine. (4) No O-linked carbohydrate moieties are present on the receptor molecule.