FhGST-S1 was amplified via PCR using the following primer pair: rFhGST-S1 forward primer, 59 GGAATTCCATATGGA-CAAACAGCATTTCAAGTT 39;rFhGST-S1 reverse primer, 59 ATAAGAATGCGGCCGCCTAGAATGGAGTTTTTGCAC-GTTTTTT 39. Restriction enzyme sites (in bold type and underlined) for NdeI (forward primer) and NotI (reverse primer) were included so that the entire ORF could be directionally cloned into the pET23a (Novagen) vector. Recombinant protein was produced in Escherichia coli BL21(DE3) cells (Novagen).