A UNIQUE MULTIFUCOSYLATED -3GALNAC-BETA-1-]4GLCNAC-BETA-1-]3GAL-ALPHA-1- MOTIF CONSTITUTES THE REPEATING UNIT OF THE COMPLEX O-GLYCANS DERIVED FROM THE CERCARIAL GLYCOCALYX OF SCHISTOSOMA-MANSONI
Kh. Khoo et al., A UNIQUE MULTIFUCOSYLATED -3GALNAC-BETA-1-]4GLCNAC-BETA-1-]3GAL-ALPHA-1- MOTIF CONSTITUTES THE REPEATING UNIT OF THE COMPLEX O-GLYCANS DERIVED FROM THE CERCARIAL GLYCOCALYX OF SCHISTOSOMA-MANSONI, The Journal of biological chemistry, 270(29), 1995, pp. 17114-17123
The entire surface of the cercarial stage of the human blood fluke Sch
istosoma mansoni is covered by a 1-mu m thick, highly immunogenic, fuc
ose-rich glycocalyx (GCX). Using strategies based on enzymatic, chemic
al, and mass spectrometric analysis, we have defined the structures of
the major glycans released by reductive elimination from GCX. They co
mprise a heterogeneous population of multifucosylated complex oligosac
charides with the following nonreducing terminal sequences: +/- Fuc al
pha 1 --> 2Fuc alpha 1 --> 3GalNAc beta 1 --> 4GlcNAc beta 1 --> 3Gal
alpha 1 --> 3 (up arrow) +/- Fuc alpha 1 --> 2Fuc alpha 1 --> 2Fuc alp
ha 1 STRUCTURE 1 Our structural data suggest that these tri- to pentaf
ucosylated epitopes are carried on type 1, R-->Gal beta-1-->3GalNAc, a
nd type 2, R-->Gal beta 1-->3(R-->GlcNAc beta-1-->6)GalNAc, core struc
tures via repeat units of (3GalNAc beta 1-->4(Fuc alpha 1-->2Fuc alpha
1-->2Fuc alpha 1--3_GlcNAc beta-1-->3Gal alpha-->)(n)), where it is m
ainly 0 and 1, and all sugars are in the pyranose form, The proposed s
tructure represents the first instance where an alpha-galactosylated b
eta-GalNAc(1-->4)-beta-GlcNAc sequence occurs as a repeating unit in a
glycoprotein. It is also unique in being substituted with oligofucosy
l appendages. The unusual oligosaccharide structures described here, p
articularly the potentially immunodominant oligofucosyl moieties, are
most likely responsible for the known potency of GCX in modulating var
ious immune responses including complement activation, B cell mitogene
sis, and delayed type hypersensitivity in schistosomiasis.