N-linked glycans in Plasmodium

Shantha Raju sraju at gene.COM
Wed Mar 12 17:40:28 EST 1997


In contrast to that observation, in a recent report in JBC, the authors
indicated the presence of N-linked oligosaccharides in Plasmodium. I
appended the abstract below for the info. As the authors claim, there
seems to be a lot of contraversy in the field. I think this paper adds
to that contraversy rather than clearing it. Hence someone working in
the field should do the real structural work!
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Glycosylphosphatidylinositol Anchors Represent the Major Carbohydrate
Modification in Proteins of Intraerythrocytic Stage Plasmodium
falciparum*
(Received for publication, May 17, 1996, and in revised form, October
24, 1996)
D. Channe Gowda=!, Priyadarshan Gupta, and Eugene A. Davidson
>From the Department of Biochemistry and Molecular Biology, Georgetown
University Medical Center, Washington, D. C. 20007
The nature and extent of carbohydrate modification in intraerythrocytic
stage Plasmodium falciparum pro-teins have been controversial. This
study describes the characterization of the carbohydrates in
intraerythro-cytic P. falciparum proteins and provides an overall
picture of the nature of carbohydrate modification in the parasite
proteins. P. falciparum strains were meta-bolically labeled with
radioactive sugar precursors and ethanolamine at different developmental
stages. The in-dividual parasite proteins separated on
SDS-polyacryl-amide gels and whole parasite cell lysates were analyzed
for the carbohydrate moieties. The results established the following: 1)
glycosylphosphatidylinositol (GPI) an-chors represent the major
carbohydrate modification in the intraerythrocytic stage P. falciparum
proteins; 2) in contrast to previous reports, O-linked carbohydrates are
either absent or present only at very low levels in the parasite; and 3)
P. falciparum contains low levels of N-glycosylation capability. The
amount of N-linked car-bohydrates in whole parasite proteins is ;6%
compared with the GPI anchors attached to proteins based on radioactive
GlcN incorporated into the proteins. The glycan cores of multiple
parasite protein GPI an-chors are all similar, consisting of
protein-ethanol-amine- phosphate-(Mana1-2)6Mana1-2Mana1-6Mana1- 4GlcN.
The fourth Man residues distal to GlcN of the GPI anchor glycan cores
contain unidentified substituents that are susceptible to conditions of
nitrous acid deami-nation. This unusual structural feature may
contribute to the reported pathogenic properties of the P. falcipa-rum
GPI anchors.
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T. Shantha Raju



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