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BO NILSSON, SAUL W. ROSEN, BRUCE D. WEINTRAUB, DAVID A. ZOPF, Differences in the Carbohydrate Moieties of the Common α-Subunits of Human Chorionic Gonadotropin, Luteinizing Hormone, Follicle-Stimulating Hormone, and Thyrotropin: Preliminary Structural Inferences from Direct Methylation Analysis, Endocrinology, Volume 119, Issue 6, 1 December 1986, Pages 2737–2743, https://doi.org/10.1210/endo-119-6-2737
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Abstract
The carbohydrate components of combined asubunits of urinary hCG and human pituitary LH (hLH), FSH (hFSH), and TSH (hTSH), each derived from the intact hormone, were studied by direct sugar analysis and methylation analysis. The methods provide a complete survey of the structural elements contained in the complex sugars associated with these glycoproteins, but do not establish the sugar sequences or anomeric configurations of glycosidic bonds. By analogy to N-linked oligosaccharides that occur in many glycoproteins, the data suggest distinct structural features for carbohydrates of asubunits combined with β-subunits. hCGα contains biantennary asparagine-linked chains terminated by either NeuAcα2- 3Galβ1- or GlcNAcβ1-2 Manαl- and lacks fucose. hTSHα contains biantennary chains with the same termini as hCGa plus terminal R-O-4GalNAc and a fucosyl residue linked α1–6 to the inner GlcNAc residue of the N-linked chitobiosyl core. hLHα may contain some high mannose chains, but primarily contains biaritennary chains terminated by NeuAcα2-3(6)Galβl-, GlcNAcβ1-, GalNAc-1-, R’-O-6GlcNAc-l-, and R“-0-2Man-lplus a fucosyl residue linked al-6 to the inner GlcNAc residue of the N-linked chitobiosyl core. hFSHα contains more complicated structures that probably include a bisecting GlcNAc residue linked β1-4 to a 3,6-di-O-substituted core mannosyl residue, and terminal NeuAca2-3Galβ1-4(±Fucal-3)GlcNAc-l, Galβ1–4(±Fucal-3)GlcNAc-l-, R’“-O-GalNAc-l-, and GalNAc-1. In addition, the presence of 2,4-di-O-substituted mannose in hFSHa indicates that it contains triantehnary chains. The identities of the R; R’, R“, and R’“ groups were not determined, but recent studies of glycoprotein hormones suggest that they may be sulfate groups. Our results demonstrate differential glycosylation of virtually identical polypeptide hormone α-subunits produced in the same organ or perhaps even in the same cell. {Endocrinology 119: 2737-2743,1986)
