Fig. 2. Expression and analysis of recombinant TgSODB2. (A) Schematic of constructs used in this study including two E. coli N-terminally histidine-tagged (His) expression constructs: hisrSOD^26-287 contains the presequence (PS) and the SOD domain, and his-rSOD^85-287 consists of the SOD domain alone. An arrow denotes the approximate position of cleavage of his-rSOD^26-287 by an endogenous E. coli protease. (B) Coomassie Blue-stained SDS-PAGE gels showing insoluble (insol) and soluble (sol) fractions of E. coli expressing his-rSOD^26-287 and his-rSOD^85-287 and final purification of his-rSOD^85-287 (pure). The open arrowhead denotes the position of his-rSOD^26-287 in the insoluble fraction; closed arrows denote the position of his-rSOD^85-287 in the soluble fraction of induced cells. (C) SOD activity assay using native gel electrophoresis. A 12.5% polyacrylamide gel was first stained for SOD activity (see Materials and Methods) and then stained with Coomassie Blue. Light areas indicate regions of SOD activity: 10 µg E. coli FeSOD (positive control), 10 µg purified rSOD^85-287 showing strong dismutase activity, and 15 µg purified recombinant T. gondii MIC5 (negative control).