The variant surface glycoproteins (VSGs) of Trypanosoma brucei are attached to the plasma membrane via a glycosylphosphatidylinositol (GPI) membrane anchor, This anchor contains the core sequence ethanolamine-PO4-6Mana1-2Mana1-6Mana1-4GlcNa1-6myo- inositol, which is conserved in all GPI anchors, and a unique aGal side chain attached to the 3-position of the aMan residue adjacent to the aGlcN residue. Here we report that trypanosome membranes can catalyse the transfer of Gal from UDP-Gal to the hydrophobic thioglycoside Mana1-6Mana1-S-(CH2)7-CH2. Characterization of the galactosylated products by electrospray mass spectrometry, exoglycosidase digestion and periodate-oxidation studies revealed that the major product was Mana1-6(Gala1-3)Mana1-S-(CH2)7-CH2. The similarity of this product to part of the mature VSG GPI anchor suggests that the thioglycoside is able to act as an acceptor for the trypanosome-specific UDP-Gal-GPI anchor a1,3-galactosyltransferase.
|Number of pages||6|
|Publication status||Published - 1 Jan 1995|