Figure 5.

ValA overlay with closed and open DHQS structures. Shown are ribbon diagrams of an unliganded, open DHQS (blue, PDB entry 1NRX), a CBP-bound, closed DHQS (cyan, PDB entry 1DQS), and ValA (purple), all overlaid on the basis of their NAD⁺-binding domains. Pale hues are used for the NAD⁺-binding domains and NAD⁺ and dark hues for the metal-binding domains. For the sake of clarity, only select secondary structure elements of the metal-binding domain are shown along with the three zinc-ligating residues (sticks) and the zinc (gray sphere). The active site side chain that does not align well between DHQS (Arg264) and ValA (Arg277) is colored green for both structures, and the alternate equivalent ValA residue (Arg278) is colored orange. The fact that other open DHQS structures, such as those of TtDHQS (PDB entry 1UJN) and HpDHQS (PDB entry 3CLH), are up to 5° different in domain orientation compared with AnDHQS (PDB entry 1NRX) does not alter the conclusions of this analysis.