286
Carbohydrate Antigens
Gal
Gal
Glc
Cer
GlcNAc
Fuc
b
1-3
a
1-4
Le
a
Gal
Gal
Glc
Cer
GlcNAc
Fuc
b
1-4
a
1-3
Le
x
(SSEA-1)
Sialyl Le
x
Gal
Gal
Glc
Cer
GlcNAc
Fuc
b
1-3
a
1-4
Fuc
a
1-2
Le
b
Gal
Gal
Glc
Cer
GlcNAc
Fuc
b
1-4
a
1-3
NeuAc
a
2-3
(a) Lewis system
Lec - 1
l
Gal
Gal
Glc
Cer
GlcNAc
b
1-3
b
1-3
b
1-4
b
1-1
Gal
Gal
GlcNAc
Gal
Gal
Cer
GlcNAc
GlcNAc
b
1-4
b
1-3
b
1-6
Lec - 2
Gal
Gal
Gal
Fuc
Gal
Glc
Cer
GlcNAc
GlcNAc
GlcNAc
b
1-3
a
1-3
b
1-4
b
1-6
i
Gal
Gal
Gal
Cer
GlcNAc
GlcNAc
b
1-4
b
1-3
(b) I and i antigens
Fig. 5
Schematics of blood group substances I, i, and Le series. This diagram
illustrates the rigid conformation of various terminal chain possessing
oligosaccharides. Some sugar chains represented here have had
α
(1
2)linked
fucosyl residues added to create the terminal branches of the human blood group
substances. (a) Lewis (Le) sugar series. (b) I and i sugar chains.
Le
a
to E-selectin was thus attributed to fa-
vorable electrostatic interactions between
the charged sulfate group and the selectin
molecules. Close packing between fucose
and galactose residues might be a ma-
jor cause of this conformational rigidity.
Such conformational rigidity is also seen
in other blood group substances.
Understanding the conformational flex-
ibility or rigidity of oligosaccharides is
important for the rational design of drugs,
vaccines, and other biological reagents
using
carbohydrate
molecules.
Recent
recognition of a conformational epitope
of a sugar chain as an effective vacci-
nation against meningococcal infections
highlights this concept. Meningococcal
meningitis is a severe childhood dis-
ease
that
often
results
in
signiFcant
disability or death. Two major etiologi-
cal agents of meningitis are the group
B
meningococci
and
capsular
type
K1
Escherichia coli
. The virulence of these
organisms is attributable to structural
mimicry between their common
α
(2–8)-
polysialic acid capsular polysaccharide and
human tissue
antigens. This property
allows the bacteria to evade immune
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