A SIMPLE PURIFICATION OF PROCYCLIC ACIDIC REPETITIVE PROTEIN AND DEMONSTRATION OF A SIALYLATED GLYCOSYL-PHOSPHATIDYLINOSITOL MEMBRANE ANCHOR

The procyclic acidic repetitive protein is the major cell-surface glyc oprotein of the insect-dwelling procyclic forms of the Trypanosoma bru cei species of African trypanosomes. The glycoprotein contains an acid ic Glu-Pro repeat domain, a glycosyl-phosphatidylinositol membrane anc hor and a putative asparagine glycosylation site. In this paper we des cribe a rapid purification scheme for this glycoprotein, using solvent extraction and hydrophobic interaction chromatography, and a partial characterization of the glycosylphosphatidylinositol membrane anchor. The carbohydrate composition of the anchor is extremely unusual; it co ntains on average nine GlcNAc, nine Gal and five sialic acid residues. This is the first description of such a heavily substituted and negat ively charged anchor. A comparison between the trypanosome procyclic s urface and the Leishmania promastigote surface is also presented.