Crystal structures of 26kDa Clonorchis sinensis glutathione S-transferase reveal zinc binding and putative metal binding

•We determined the crystal structures of CsGST and D26H mutant.•Asp26, His79 of CsGST coordinate a zinc ion.•The CsGST–D26H mutant coordinates a zinc ion through four histidine residues.•The zinc ions mediate molecular contacts in the crystal. The crystal structures of CsGST in two different space groups revealed that Asp26 and His79 coordinate a zinc ion. In one space group, His46 of an adjacent molecule participates in the coordination within 2.0Å. In the other space group, Asp26, His79 and a water molecule coordinate a zinc ion. The CsGST–D26H structure showed that four histidine residues – His26 and His79 from one molecule and the same residues from a symmetry-related neighboring molecule – coordinate a zinc ion. The coordinated zinc ions are located between two molecules and mediate molecular contacts within the crystal.