Carbohydrate moiety of Plasmodium falciparum glycoproteins: the nature of the carbohydrate-peptide linkage in the MSP-2 glycoprotein.
Metabolic labelling of Plasmodium falciparum parasites with [3H]GlcN, [3H]Man, [3H]Gal and [3H]ethanolamine, and subsequent purification by SDS-PAGE of the labelled material provided effective labelling of the MSP-1, 195 kDa, and MSP-2, 42-53 kDa, glycoproteins. Reductive beta-elimination of the MSP-2 released from the gel consisted of glycopeptides containing labelled sugars. Processing of the eliminated components and identification of the sugar residues demonstrated the presence of N-acetylglucosaminitol and N-acetylgalactosaminitol amongst other labelled sugars. Reductive beta-elimination with sodium hydroxide-sodium borotritide-borohydride showed the presence of glucosaminitol and alanine in the hydrolysis products. The MSP-2 was retained on solid phase wheat-germ agglutinin and was released from the lectin by treatment with GlcNAc. Upon treatment with O-glycanase the MSP-2 glycoprotein released labelled amino sugar, and derived oligosaccharides on treatment with exoglycosidases released labelled components corresponding to the metabolically incorporated sugars. Labelled Gal was incorporated into the MSP-2 glycoprotein using [3H]UDP-Gal and galactosyltransferase. The galactosylated glycoprotein released labelled Gal upon treatment with beta-galactosidase. The results of the present study suggest that the carbohydrate chains of the MSP-2 glycoprotein are attached to the protein backbone via GlcNAc- and GalNAc-serine/threonine in O-glycosyl linkage and the glycoprotein has terminal GlcNAc and Gal residues. The carbohydrate moieties of MSP-2, glycoprotein consist mainly of short chains linked to the protein core.
Khan
A H
AH
Institute of Biochemistry, University of Balochistan, Quetta, Pakistan.
Qazi
A M
AM
Hoessli
D C
DC
Torred-Duarte
A P
AP
Senaldi
G
G
Qazi
M H
MH
Walker-Nasir
E
E
Nasir-ud-Din
D000818:Animals; D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D002241:Carbohydrates / Q000032:analysis*; D002845:Chromatography / Q000379:methods; D006023:Glycoproteins / Q000737:chemistry* / Q000378:metabolism; D006031:Glycosylation; D010963:Plasmodium falciparum / Q000737:chemistry* / Q000378:metabolism; D011233:Precipitin Tests; D015800:Protozoan Proteins / Q000737:chemistry* / Q000378:metabolism
D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002241:Carbohydrates; D006023:Glycoproteins; D015800:Protozoan Proteins; C103348:msp2 protein, Anaplasma marginale