Studies on the purification of Entamoeba histolytica antigens by gel filtration. I. Some physicochemical properties of the isolated fractions

Abstract

Aqueous extracts, prepared from Entamoeba histolytica (DKB strain) grown at 37 °C in TTY medium with Crithidia sp., were chromatographed on Sephadex G-200 and G-100 gels equilibrated with 0.15 M phosphate buffer, pH 7.2. Seven fractions were obtained, the molecular weights of which ranged from 650 000 to [Formula: see text]. The absorption spectra of either the whole amoebic extract or the first two fractions from the G-200 column were in the region of 280 mμ. The protein to carbohydrate ratio of the whole undialyzed amoebic extract was 2.6:1, which changed to 17:1 after dialysis, indicating a considerable loss of carbohydrate. The whole amoebic extract when subjected to disc electrophoresis resolved into 26 protein bands while the fractions, in addition to having contaminants from the preceding peaks, also contained their own characteristic protein bands. The first two fractions contained, as determined by disc electrophoresis and isoelectric focusing, a variety of different anionic proteins. The isoelectric pH of the first fraction was 5.8 to 6.0 and that of the second ranged between 4.5 and 6.4.