Oct 15, 1989

Site-specific processing of the N-linked oligosaccharides of the human chorionic gonadotropin alpha subunit

The Journal of Biological Chemistry
M BielinskaI Boime

Abstract

Two forms of the gonadotropin alpha subunit are synthesized in placenta and in human chorionic gonadotropin (hCG)-producing tumors: an uncombined (monomer) form and a combined (dimer) form. These forms show differences in their migration on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The slower migration of the monomeric form on sodium dodecyl sulfate-polyacrylamide gel electrophoresis has been attributed to a different glycosylation pattern. Previous studies demonstrated different roles of each of the two alpha N-linked glycosylation sites (Asn-52 and Asn-78) in secretion of the uncombined subunit and the biologic activity of hCG dimer. To assess the influence of formation of dimer on the processing pattern at the individual sites, we characterized the N-linked oligosaccharides of monomer and dimer forms of recombinant human choriogonadotropin alpha subunit. Two approaches were employed. First, site-directed mutagenesis was used to alter the two N-linked oligosaccharide attachment sites, thus allowing the expression of alpha subunits containing only one glycosylation site. Second, tryptic glycopeptides of the wild-type subunits were examined. Concanavalin A (ConA) binding and sialic acid content indicated that t...Continue Reading

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Mentioned in this Paper

Asparagine
Structure-Activity Relationship
SDS-PAGE
Proteins, Recombinant DNA
Neoplasms
High Pressure Liquid Chromatography Procedure
Protein Glycosylation
Glycoprotein Hormones, alpha Subunit
Sialic Acids
Xicil

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