Biosynthesis of a variant surface glycoprotein of Trypanosoma brucei. Processing of the glycolipid membrane anchor and N-linked oligosaccharides.

J. D. Bangs, T. L. Doering, P. T. Englund, Gerald Warren Hart

Research output: Contribution to journalArticle

Abstract

The variant surface glycoprotein (VSG) of the ILTat 1.3 variant of Trypanosoma brucei has two asparagine-linked glycan moieties, as well as a phosphatidylinositol glycan membrane anchor. We have investigated the structure and processing of each of these oligosaccharides through analysis of the intact protein and of glycopeptides. Processing has been examined by comparing glycan structures purified from an immature intracellular form (58 kDa) of VSG with those of the mature form (59 kDa) found on the parasite surface. We find exclusively high mannose oligosaccharides (Man4-7-GlcNAc2) at Asn-432 in both the immature 58-kDa and mature 59-kDa forms. In contrast, the "core" oligosaccharide of Asn-419 (Man3-GlcNAc2) appears to be nearly quantitatively processed to a complex biantennary structure [Gal-GlcNAc-Man)2-Man-GlcNAc2) during VSG maturation. The asparagine-linked structures at Asn-419, but not those at Asn-432, are resistant to endo-beta-N-acetylglucosaminidase H within 30 s of biosynthesis. This suggests possible novel and selective mechanisms for glycosylation in African trypanosomes. Finally, we show that the carboxyl-terminal glycolipid is galactosylated (3-4 residues) relatively late in VSG biosynthesis. Phosphatidylinositol glycans have been identified on a growing number of eukaryotic membrane proteins. This report provides a direct demonstration of the processing of such a glycolipid anchor following its attachment to protein.

Original languageEnglish (US)
Pages (from-to)17697-17705
Number of pages9
JournalJournal of Biological Chemistry
Volume263
Issue number33
StatePublished - Nov 25 1988

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Trypanosoma Variant Surface Glycoproteins
Trypanosoma brucei brucei
Glycolipids
Biosynthesis
Membrane Glycoproteins
Anchors
Oligosaccharides
Membranes
Glycosylphosphatidylinositols
Asparagine
Processing
Polysaccharides
Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase
Glycosylation
Trypanosomiasis
Glycopeptides
Mannose
Membrane Proteins
Parasites
Proteins

ASJC Scopus subject areas

  • Biochemistry

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Biosynthesis of a variant surface glycoprotein of Trypanosoma brucei. Processing of the glycolipid membrane anchor and N-linked oligosaccharides. / Bangs, J. D.; Doering, T. L.; Englund, P. T.; Hart, Gerald Warren.

In: Journal of Biological Chemistry, Vol. 263, No. 33, 25.11.1988, p. 17697-17705.

Research output: Contribution to journalArticle

Bangs, J. D. ; Doering, T. L. ; Englund, P. T. ; Hart, Gerald Warren. / Biosynthesis of a variant surface glycoprotein of Trypanosoma brucei. Processing of the glycolipid membrane anchor and N-linked oligosaccharides. In: Journal of Biological Chemistry. 1988 ; Vol. 263, No. 33. pp. 17697-17705.
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