Structural basis for catalytic activity of a silkworm Delta-class glutathione transferase

► We determined the crystal structure of Delta-class GST from Bombyx mori (bmGSTD). ► Secondary and tertiary structures are highly conserved in bmGSTD. ► bmGSTD is stabilized by a hydrophobic lock-and-key motif. ► We determined crucial residues for glutathione binding by site-directed mutagenesis. ► Our study reveals possible catalysis mechanisms in glutathione conjugation of bmGSTD.