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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!
Glycosylphosphatidylinositol Anchors Represent the Major Carbohydrate
Modification in Proteins of Intraerythrocytic Stage Plasmodium
(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.
T. Shantha Raju

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