FIGURE 5.

Substrate-binding sites of PcGSTO1 and HsGSTO1-1 (10). Top, stereo view of the hydrogen bond network formed by the active site residues around GSH in PcGSTO1. The schematic trace of the polypeptide main chain is suggested in cyan (thioredoxin-like domain) and purple (α-helix domain). Middle, PcGSTO1 electrostatic surface (blue, positive charge; red, negative charge) of PcGSTO1 in the region of GSH (shown as sticks). Left panel, calculated with all the residues observed for monomer A in the crystallographic model (Glu³⁸–Asp³⁵¹); middle panel, calculated without the N-terminal coil (i.e. with residues Tyr⁷⁸–Asp³⁵¹); right panel, same as previous but without Arg¹⁵⁵. Bottom, HsGSTO1-1 active site compared with PcGSTO1. Left panel, electrostatic surface calculated for the HsGSTO1-1dimer, in the region of GSH (shown as sticks). Right panel, stereo view of the accessible surface of HsGSTO1-1 (gray) in the region of GSH (green), superimposed to the PcGSTO1 active site containing the GSH (blue sticks). Residues Tyr²²³, Tyr³²⁶, and His³³⁰ fill the pocket defined by Board et al. (10) as the HsGSTO1-1 active site. Residues in cyan and in orange form a second and a third layers of residues that almost close the PcGSTO1 active site.