Expression and Characterization of a Sigma-Class Glutathione S-transferase of the Oriental Migratory Locust, Locusta migratoria manilensis (Meyen)

A cDNA encoding a sigma-class glutathione S-transferase of the locust, Locusta migratoria manilensis (LmGSTsl), was cloned by reverse transcriptase-polymerase chain reaction. The 830 bp-long cDNA encoded a 615 bp open reading frame (204 amino acid polypeptide), which exhibited the structural motif and domain organization characteristic of GST sigma-class. It revealed 59, 57, 57, and 56% identities to sigma-class GSTs from Blattella germanica, Gryllotalpa orientalis, Nasonia vitripennis, and Pediculus humanus corporis, respectively. A recombinant protein (LmGSTsl) was functionally expressed in Escherichia coli cells in a soluble form and purified to homogeneity. LmGSTsl was able to catalyze the biotranslation of glutathione with l-chloro-2,4-dinitrobenzene, a model substrate for GSTs, as well as with/?-nitro-benzyl chloride. Its optimal activity was observed at pH 8.0 and at 30°C. Incubation for 30 min at temperatures below 50°C scarcely affected the activity. The I50 of reactive blue (RB) was 18.5 umol L-1. In the presence of 0.05 mmol L-1 ethacrynic acid (ECA), LmGSTsl showed (81±3)% of the original activities.