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Y’VONNE R. JONES-BROWN, CHOU Y. WU, BRUCE D. WEINTRAUB, SAUL W. ROSEN, Synthesis of Chorionic Gonadotropin Subunits in Human Choriocarcinoma Clonal Cell Line JEG-3: Carbohydrate Differences in Glycopeptides from Free and Combined α-Subunits, Endocrinology, Volume 115, Issue 4, 1 October 1984, Pages 1439–1445, https://doi.org/10.1210/endo-115-4-1439
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Abstract
The glycoprotein hormone hCG and its free asubunit are secreted by the clonal choriocarcinoma cell line JEG-3. Free hCGα has a larger apparent mol wt (22,000–24,000) than the combined hCGα (18,000–19,000) obtained by dissociation of the hCG secreted by these cells. Techniques developed for the specific isolation and purification of the free and combined hCGα forms and for the preparation of glycopeptides from these subunits have permitted detection of the incorporation of d-[3H]glucosamine ([3H]GlcN) and l-[3H]fucose into both asubunit forms. Relative to their [3SS]methionine content, 2.3-fold more [3H]GlcN and 6-fold more l-[3H]fucose were incorporated into free hCGα than into combined hCGα. Analyses of [3H]GlcN glycopeptides prepared from free and combined hCGα indicate that the 22,000- to 24,000-dalton subunit form contained more [3H]GlcN and 27% more of the GlcN metabolite Nacetylneuraminic acid than the 18,000- to 19,000-dalton hCG asubunit, than both hCGα forms contained two major N-linked oligosaccharide chains differing primarily in their NeuAc content, and that most of the [3H]GlcN was incorporated as GlcN or metabolites of GlcN other than N-acetylneuraminic acid. These studies provide direct chemical evidence of a higher content of carbohydrate in the larger free α-subunit form. (Endocrinology115: 1439–1445, 1984)
