Unmasking a new recognition signal for O-linked glycosylation in the chorionic gonadotropin β subunit

Vicenta Garcia-Campayo, Tadashi Sugahara, Irving Boime

Research output: Contribution to journalArticlepeer-review

9 Scopus citations

Abstract

hCGβ subunit is distinguished among the other members of the family of the glycoprotein hormones by the presence of four serine O-linked oligosaccharide units in the last 25 amino acids. This carboxy terminal peptide (CTP) influences the intracellular behavior of the subunit and is important for maintaining the biological half-life of hCG. To examine how the O-linked oligosaccharides affect the metabolic behavior of hCG, we generated a CGβ mutant devoid of the native O-linked acceptor sites. An alternative site not used in the native subunit was glycosylated and the structure of this oligosaccharide differed from the wild-type O-linked carbohydrates. This glycosylation occurred at serine 130 in the CTP and in contrast to the wild type O-linked oligosaccharides, sialic acid is a major component of the alternatively linked carbohydrate. The data show that deleting the native acceptor sites exposes a new site for O-glycosylation and promotes a differential intracellular processing of the β subunit. These results support the hypothesis that the CTP participates in the folding of the newly synthesized subunit, which is manifested by the post-translational changes reported here.

Original languageEnglish
Pages (from-to)63-70
Number of pages8
JournalMolecular and Cellular Endocrinology
Volume194
Issue number1-2
DOIs
StatePublished - Aug 30 2002

Keywords

  • CTP
  • Gonadotropin
  • O-Glycosylation
  • Structure-function

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