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

TY - JOUR

T1 - Structure of the glycosylphosphatidylinositol membrane anchor glycan of a class-2 variant surface glycoprotein from Trypanosoma brucei

AU - Mehlert, Angela

AU - Richardson, Julia M.

AU - Ferguson, Michael A. J.

PY - 1998/3/27

Y1 - 1998/3/27

N2 - 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.

AB - 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.

KW - Trypanosome

KW - Glycosylphosphatidylinositol (GPI)

KW - VSG

KW - Glycoprotein

KW - Galactosyltransferase

U2 - 10.1006/jmbi.1997.1600

DO - 10.1006/jmbi.1997.1600

M3 - Article

SN - 0022-2836

VL - 277

SP - 379

EP - 392

JO - Journal of Molecular Biology

JF - Journal of Molecular Biology

IS - 2

ER -