Nucleotide and deduced amino acid sequences of GSTO2 gene of F. hepatica. The start and stop codons are indicated in bold and “*”. The conservative cysteine residues are shown by a box, while the GST_N and GST_C regions are indicated by underline and wave, respectively. The α-helicals, β-strands, glutaredoxin active site and glutathione-binding residues are marked in shadow, red and italic, respectively.

Comparisons of the amino acid sequence of GSTO2 protein of F. hepatica with other trematode GSTO. The red shadow indicates that the sequence consistency is 100%, while similar residues are shown as blue box. Fh: Fasciola hepatica (AFX98104.1); Fg: Fasciola gigantica (JX157881.1); Sm: Schistosoma mansoni (AAO49385.1); Cs: Clonorchis sinensis (KX163089.1).

Identification of rGSTO2 protein of F. hepatica by SDS-PAGE and western blot. (A) Lane M, protein marker; lane 1, Sonicated supernatant of cultures after transformation of E. coli with the empty pET-28a plasmid; lane 2, lysate precipitation of rGSTO2 after induction for 6 h; lane 3-6, lysate supernatant of rGSTO2 at 2, 4, 6 and 8 hours induced by IPTG. (B) Lane M, protein marker; lane 1, purified rGSTO2 protein. (C) Lane M, protein marker; lane 1 and lane 2 were loaded with rGSTO2 protein and then incubated with sheep anti-F. hepatica sera or normal sheep serum, then incubated with HRP-conjugated rabbit anti-sheep IgG. (D) Lane M, protein marker; lane 1 and lane 2 were loaded with rGSTO2 protein and then incubated with mouse anti-rGSTO2 IgG or naïve mouse serum, respectively, and then incubated with HRP-conjugated goat anti-mouse IgG.