Molecular weight analysis of the major polypeptides and glycopeptides of Toxoplasma gondii

A soluble and an insoluble fraction of ultrasonicated Toxoplasma gondii (RH strain) tachyzoites were prepared by ultracentrifugation. The insoluble parasite fraction was solubilized by incubation in 1% sodium deoxycholate (DOC). The molecular weights (m.w.) of the polypeptides in the fractions were determined by sodium dodecyl sulphate (SDS) - polyacrylamide gel electrophoresis (PAGE). After comparison with the m.w. of the polypeptides of appropriate controls the soluble Toxoplasma fraction contained at least 9 parasite polypeptides with m.w. of 20K, 22K, 23K, 29K, 66K, 69K, 90K, 98K and 133K and the insoluble parasite fraction contained at least 8 Toxoplasma derived polypeptides with m.w. of 28K, 41K, 43K, 49K, 53K, 61K, 70K and 80K. The presence of glycosylated polypeptides was detected by incubation of sliced gels with |¹²⁵I| Concanavalin A (Con A). The soluble Toxoplasma fraction contained no major glycopeptide bands while the insoluble parasite fraction contained at least 3 glycosylated polypeptides of Toxoplasma origin with m.w. of 29K, 53K and 123K.