FIGURE 9.

The proposed alternative substrate-binding site. The substrate (ball-and-sticks, green C atoms) was docked at the location where a GOL molecule (magenta) is present universally in all presented crystal structures. Note that the carbamoyl moiety of the substrate partially overlaps with the GOL position. The reaction intermediate, DHMP (ball-and-sticks, gray), bound in the catalytic center is shown to visualize the structural proximity of the two sites. Dashed black lines indicate possible hydrogen bonds with Asp194, His198 and Glu248. The surfaces of the two dimer-forming protein subunits are color-coded red and blue.