The hydrophobic mannoside Man alpha 1-6Man alpha 1-S-(CH2)7-CH3 acts as an acceptor for the UDP-Gal:glycosylphosphatidylinositol anchor alpha 1,3-galactosyltransferase of Trypanosoma brucei.
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-PO4-6Man alpha 1-2Man alpha 1-6Man alpha 1-4GlcN alpha 1-6myo-inositol, which is conserved in all GPI anchors, and a unique alpha Gal side chain attached to the 3-position of the alpha Man residue adjacent to the alpha GlcN residue. Here we report that trypanosome membranes can catalyse the transfer of Gal from UDP-Gal to the hydrophobic thioglycoside Man alpha 1-6Man alpha 1-S-(CH2)7-CH3. Characterization of the galactosylated products by electrospray mass spectrometry, exoglycosidase digestion and periodate-oxidation studies revealed that the major product was Man alpha 1-6(Gal alpha 1-3)Man alpha 1-S-(CH2)7-CH3. 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 alpha 1,3-galactosyltransferase.
Pingel
S
S
Physiologisch-chemisches Institut, Universität Tübingen, Federal Republic of Germany.
Field
R A
RA
Güther
M L
ML
Duszenko
M
M
Ferguson
M A
MA
D000818:Animals; D002240:Carbohydrate Sequence; D002851:Chromatography, High Pressure Liquid; D002855:Chromatography, Thin Layer / Q000379:methods; D005690:Galactose / Q000378:metabolism; D005700:Galactosyltransferases / Q000378:metabolism*; D017261:Glycosylphosphatidylinositols / Q000378:metabolism*; D013058:Mass Spectrometry / Q000379:methods; D008969:Molecular Sequence Data; D013865:Thioglycosides / Q000302:isolation & purification / Q000378:metabolism*; D014346:Trypanosoma brucei brucei / Q000201:enzymology*
D017261:Glycosylphosphatidylinositols; C095087:Man alpha1-6Man alpha1-S-(CH2)7-CH3; D013865:Thioglycosides; D005700:Galactosyltransferases; C037959:beta-D-galactosyl-N-acetylglucosaminylglycopeptide alpha-1,3-galactosyltransferase; D005690:Galactose