Crystallographic survey of active sites of an unclassified glutathione transferase from Bombyx mori

► The crystal structure of bmGSTu has been determined with a resolution of 2.1 Å. ► Bound glutathione could be localized at the G-site. ► Recombinant bmGSTu catalyzed transfer of glutathione to a synthetic GST substrate. ► Val55, Glu67, and Ser68 in the G-site are catalytically important. ► The H-site shows unique features that may have relevance to pest control.