CHARACTERIZATION OF A SMALL VARIABLE SURFACE GLYCOPROTEIN FROM TRYPANOSOMA-VIVAX

Several biochemical properties of a variant surface glycoprotein (VSG) from the parasite Trypanosoma (Duttonella) vivax have been determined . ILDat 2.1 VSG is approximately 40 kDa in size making this the smalle st trypanosome VSG described to date. The glycolipid anchor of ILDat 2 .1 VSG is resistant to treatment with T. brucei-derived phospholipase C and data based on lectin affinity chromatography, incorporation of r adiolabelled sugar and treatment with endoglycosidase H suggest that t he T. vivax VSG bears little carbohydrate. cDNA to ILDat 2.1 VSG mRNA has been cloned and the encoded protein sequence includes the N-termin al amino acid peptide sequence derived from native VSG. The molecular weight of the VSG predicted from the translated cDNA sequence is simil ar to that of the native molecule and in support of the biochemical da ta it is devoid of sites for N-linked glycosylation. Examination of th e deduced ILDat 2.1 VSG protein sequence reveals that it is most simil ar to T. congolense VSGs in the distribution of Cys residues and like the former it does not contain any of the defined VSG C-terminal domai n types. However, unlike T. congolense VSGs it does not readily fit in to the currently described VSG N-terminal domain types. Our studies su ggest that ILDat 2.1 VSG is distinct from any of the previously charac terized VSGs.