Biophysical characterization, crystallization, and solution of the first crystal structure of the 28 kDa-Schistosoma bovis glutathione transferase

Glutathione S-transferase (GST) is a potential therapeutic drug target against helminthic diseases. This essential enzyme prevents oxidative stress by inhibiting the toxic build-up of xenobiotics in the worm during human host infection. Schistosoma schistosome manifests two GST isoforms, namely the 26- and 28-kDa GST, which exhibit contrasting substrate specificities within the worm. This study was designed to explore the structural and functional relationships of Schistosoma bovis 28 kDa-GST (Sb28GST) through crystallographic studies. The 1Chloro-2,4-Dinitrobenzene-Glutathione assay revealed that the enzyme was catalytically active. The secondary structural content confirmed that Sb28GST follows a canonical GST fold, mostly alpha -helical. Extrinsic 1-anilinonaphthalene-8-sulfonic acid substitution revealed buried hydrophobic clefts within the enzyme. Sb28GST was purified by immobilised metal affinity chromatography. Crystal structures of Sb28GST were determined for the un-ligated enzyme (resolution = 2.3 angstrom, Rfactor = 21.68 %). The crystals belonged to the monoclinic space group P21, which accommodated two biological molecules in the asymmetric unit with the unit -cell parameters of a = 54.133, b = 77.086, c = 54.015 angstrom and beta = 93.15 Computational modelling studies predicted the catalytic propensity of 8ALS may vary from that of 1OE8 by differences in the molecular dynamic trajectory, especially at the dimer interface of this obligate dimeric enzyme.