Structure of the glycosylphosphatidylinositol membrane anchor glycan of a class-2 variant surface glycoprotein from Trypanosoma brucei

Angela Mehlert, Julia M. Richardson, Michael A. J. Ferguson

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    Abstract

    The neutral glycan fraction of the glycosylphosphatidylinositol (GPI) membrane anchor of a class-2 variant surface glycoprotein (VSG) from Trypanosoma brucei was isolated following aqueous hydrogen fluoride dephosphorylation and nitrous acid deamination of the purified glycoprotein. The neutral glycans were fractionated by high-pH anion exchange chromatography and gel-filtration and six major glycan structures were solved by a combination of one and two-dimensional NMR, composition analysis, methylation linkage analysis and electrospray-mass spectrometry. The glycans were similar to those previously described for class-1 VSGs, in that they contained the linear trimannosyl sequence Man alpha 1-2Man alpha 1-6Man and a complex alpha-galactose branch of up to Gal alpha 1-2Gal alpha 1-6(Gal alpha 1-2)Gal, but most also contained an additional galactose residue attached alpha 1-2 to the non-reducing terminal mannose residue and about one-third contained an additional galactose residue attached beta 1-3 to the middle mannose residue. The additional complexity of the class-2 VSG GPI glycans is discussed in terms of a biosynthetic model that explains the full range of mature GPI structures that can be expressed on different VSG classes by the same trypanosome clone. (C) 1998 Academic Press Limited.

    Original languageEnglish
    Pages (from-to)379-392
    Number of pages14
    JournalJournal of Molecular Biology
    Volume277
    Issue number2
    DOIs
    Publication statusPublished - 27 Mar 1998

    Keywords

    • Trypanosome
    • Glycosylphosphatidylinositol (GPI)
    • VSG
    • Glycoprotein
    • Galactosyltransferase

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