trans

240 TRYPANOSOMATID CARBOHYDRATES
Crithidia fasciculata lipoarabinogalactan(LAG)
[Ara1,2] ~8 -[Galβ1-3] 12 -Galβ1-3Galβ1-3Gal f β1-3Manα1-3Manα1-4GlcNα1-3-Inos-PO 4 -Ceramide
PO 4
αGlc
FIGURE 10.6
Structure of lipoarabinogalactan (LAG) from Crithidia fasciculata.
is [Ara p 1-2] x -[Gal1,3] n -Gal(1,3) Gal(1,3)Gal f
(1,3)Man(1,3)Man(1,4)GlcN(1,6)-inositol
phosphoceramide. The unusual D-Ara p has
been found in E. schaudinni and the LPG of
Leishmania. Earlier studies reported the presence
of soluble arabinogalactan (Gorin et al.,
1979), but purification procedures used at the
time probably resulted in hydrolysis of the
molecule at the galactofuranose residue. Thus,
the soluble glycan probably corresponds to the
lipid-anchored lipoarabinogalactan reported
by Schneider and colleagues.
Interestingly, sialic acid-bearing glycoconjugates
have been identified on the surface of
Crithidia, although the structures of these molecules
are unknown. The presence of sialoglycoconjugates
in Crithidia growing in sialic
acid-free chemically defined medium suggests
that the residues are synthesized de novo and
not transferred from existing glycoconjugates
by a trans-sialidase, as observed in other
trypanosomatids.
FURTHER READING
Ferguson, M.A.J. (1997). The surface glycoconjugates
of trypanosomatid parasites. Philos. Trans.
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Ferguson, M.A.J. (1999). The structure, biosynthesis
and functions of glycosylphosphatidylinositol
anchors, and the contributions of trypanosome
research. J. Cell Sci. 112, 2799–2809.
Ilg, T. (2000). Proteophosphoglycans of Leishmania.
Parasitol. Today 16, 489–497.
Ilg, T., Handman, E. and Stierhof, Y.D. (1999).
Proteophosphoglycans from Leishmania promastigotes
and amastigotes. Biochem. Soc. Trans.
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Ilgoutz, S.C. and McConville, M.J. (2001). Function
and assembly of the Leishmania surface coat.
Int. J. Parasitol. 31, 899–908.
Mengeling, B.J., Beverley, S.M. and Turco, S.J. (1997).
Designing glycoconjugate biosynthesis for an
insidious intent: phosphoglycan assembly in
Leishmania parasites. Glycobiology 7, 873–880.
Sacks, D.L. (2001). Leishmania–sand fly interactions
controlling species-specific vector competence.
Cell. Micro. 3, 189–196.
Sacks, D. and Kamhawi, S. (2001). Molecular aspects
of parasite–vector and vector–host interactions
in leishmaniasis. Annu. Rev. Microbiol. 55,
453–483.
Schenkman, S., Eichinger, D., Pereira, M.E.A. and
Nussenzweig, V. (1994). Structural and functional
properties of Trypanosoma trans-sialidase. Annu.
Rev. Microbiol. 48, 499–523.
Turco, S.J., Spath, G.F. and Beverley, S.M. (2001). Is
lipophosphoglycan a virulence factor? A surprising
diversity between Leishmania species. Trends
Parasitol. 17, 223–226.
BIOCHEMISTRY AND CELL BIOLOGY: PROTOZOA