ROLE OF CELL-SURFACE CARBOHYDRATES IN MALARIA

Metabolic labelling of Plasmodium falciparum malarial parasites with [ H-3]-glucosamine, [H-3]-galactose, [H-3]-mannose, [H-3]-ethanolamine a nd [H-3]-myristic acid and subsequent purification in SDS-PAGE yielded , amongst other proteins, the 195 KDa glycoprotein, which is the major merozoite surface antigen. Reductive B-elimination of the glycoprotei n in the gel released labelled sugars. Processing of the reaction prod ucts and acid hydrolysis of the derived sugars suggested the presence of N-acetylglucosaminitol, N-acetylglucosamine and other components. A cid hydrolysis of the labelled glycoprotein and examination of the pro ducts by chromatography indicated the presence of glucosamine, galacto se, mannose, ethanolamine and myristic acid. The 195 KDa glycoprotein was adsorbed by wheat germ agglutinin and desorbed with N-acetylglucos amine. Labelled galactose was incorporated in the glycoprotein by trea tment with [H-3]-UDP-galactose and bovine milk galactosyl transferase. The externally glycosylated glycoprotein released labelled galactose on treatment with B-galactosidase. The carbohydrate chains in the 195 KDa glycoprotein are linked to the protein core through O-glycosyl lin kage and N-acetylglucosamine and serine residues are involved in the l inkage region.