Structural characterization of the major glycosylphosphatidylinositol membrane-anchored glycoprotein from epimastigote forms of Trypanosoma cruzi Y-strain.
We have investigated the structure of the glycosylphosphatidylinositol (GPI) anchor and the O-linked glycan chains of the 40/45-kDa glycoprotein from the cell surface of the protozoan parasite Trypanosoma cruzi. This glycoconjugate is the major acceptor for sialic acid transferred by trans-sialidase of T. cruzi Y-strain, epimastigote form. The GPI anchor was liberated by treatment with hot alkali, and the phosphoinositol-oligosaccharide moiety was characterized and shown to have the following structure. [formula: see text] Unusually the glucosamine was 6-O-substituted with 2-aminoethylphosphonate, and 2-aminoethylphosphonate was also present on the third mannose residue distal to glucosamine, partially replacing the ethanolamine phosphate. The beta-eliminated reduced oligosaccharide chains showed that two novel classes of O-linked N-acetylglucosamine oligosaccharide were present. The first series had the structures Galp beta 1-3GlcNAc-ol; Galp beta 1-6(Galp beta 1-3)GlcNAc-ol; and Galp beta 1-2Galp beta 1-6(Galp beta 1-3)GlcNAc-ol, whereas the other series had a 1-4 linkage to N-acetylglucosaminitol and had structures Galp beta 1-4GlcNAc-ol, Galp beta 1-6(Galp beta 1-4)GlcNAc-ol, and Galp beta 1-2Galp beta 1-6(Galp beta 1-4)GlcNAc-ol. We have also investigated the kinetics of in vitro sialylation of these O-linked oligosaccharides by the T. cruzi transsialidase and have shown that incorporation of one molecule of sialic acid hinders entry of a second molecule when two potential acceptor sites are present.
Previato
J O
JO
Departamento de Microbiologia Geral, Universidade Federal do Rio de Janeiro, Brazil.
Jones
C
C
Xavier
M T
MT
Wait
R
R
Travassos
L R
LR
Parodi
A J
AJ
Mendonça-Previato
L
L
D000818:Animals; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D002241:Carbohydrates / Q000032:analysis; D004591:Electrophoresis, Polyacrylamide Gel; D008401:Gas Chromatography-Mass Spectrometry; D017261:Glycosylphosphatidylinositols / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D008562:Membrane Glycoproteins / Q000096:biosynthesis / Q000737:chemistry* / Q000302:isolation & purification; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000737:chemistry* / Q000302:isolation & purification; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D010716:Phosphatidylinositols / Q000378:metabolism; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism; D015800:Protozoan Proteins / Q000096:biosynthesis / Q000737:chemistry* / Q000302:isolation & purification; D014349:Trypanosoma cruzi / Q000378:metabolism*
D002241:Carbohydrates; D017261:Glycosylphosphatidylinositols; D008562:Membrane Glycoproteins; D009844:Oligosaccharides; D010716:Phosphatidylinositols; D015800:Protozoan Proteins; D010727:Phosphoric Diester Hydrolases; D043265:Phosphatidylinositol Diacylglycerol-Lyase