Characterization of the E26H Mutant Schistosoma japonicum Glutathione S-Transferase.

Glutathione-S-transferase, such as that of Schistosoma japonicum (sjGST) belongs to the most widely utilized fusion tags in the recombinant protein technology. The E26H mutation of sjGST has already been found to remarkably improve its ability for binding divalent ions, enabling its purification with immobilized metal affinity chromatography (IMAC). Nevertheless, most characteristics of this mutant remained unexplored to date. In this study, we performed a comparative analysis of the wild-type and the E26H mutant sjGST by using in vitro as well as in silico approaches. We confirmed that the sjGST(E26H) protein exhibits significantly increased affinity for binding nickel ions as compared to the wild-type. In addition, we proved that the sjGST(E26H) can be purified efficiently either with glutathione- or immobilized metal ion-affinity chromatography, even in consecutive purification steps. The human retroviral-like aspartic protease 1 (ASPRV1) conjugated with the sjGST(E26H) fusion tag was also successfully purified by using both of these affinity chromatographic approaches. Our studies revealed that the E26H mutant sjGST can be used as a versatile affinity tag because the modified protein retains the kinetic features of the wild-type and its affinity towards glutathione, while can be purified efficiently by IMAC, as well.