Overview of GST dimer structure and substrate binding. (a) A ribbon/surface representation of a typical GST subunit (Z. mays GSTF1, pdb 1BYE), with the amino-terminal domain in green, the linker region in red, the carboxy-terminal domain in blue and the protein surface in gray. A glutathione conjugate of the herbicide atrazine in ball-and-stick representation is shown binding at the active site; the GSH-binding site (G site) is highlighted in yellow and the hydrophobic site (H site) is highlighted in blue. (b) A ribbon/surface representation of the ZmGSTF1 homodimer oriented with the amino-terminal domains at bottom left and top right and the subunits in blue and purple. The atrazine-glutathione conjugates are shown in ball-and-stick representation, bound at the active site of each subunit. The dimer is formed by a ball-and-socket interaction between the amino- and carboxy-terminal domains of the different subunits (see text for further details); the deep cleft between subunits is characteristic of phi GSTs.