A histidine substitution confers metal binding affinity to a Schistosoma japonicum Glutathione S-transferase

Glutathione S-transferases (GSTs) are multifunctional enzymes that are used as fusion tags on recombinant proteins in mammalian and Escherichia coli expression systems. We recently found that the Schistosoma japonicum GST ( SjGST) displays weak Ni 2+ ion binding affinity. Glu26 and His79 were assumed to be its Ni 2+ binding sites based on the structure of the 26-kDa Clonorchis sinensis GST. To enhance SjGST Ni 2+ binding affinity, Glu26 was mutated to His. SjGST-E26H was expressed and purified at a high concentration of imidazole to a higher purity than wild type SjGST. In addition, human biotin protein ligase fused to SjGST-E26H was purified with a immobilized Ni affinity column.