Figure 2.

(A) Octahedral binding of Ni²⁺ (green sphere) in PARP1, with 2.2 ± 0.1 Å coordination distances. Red spheres represent water molecules. The anomalous density is contoured at 5σ. (B) Active site of the hPARP1c/MC2050 complex. The inhibitor (magenta) is overlaid with F_o – F_c omit density contoured at 3σ. (C and D) Binding mode of MC2050 in the active site of hPARP1c. (E) Structural overlay of PARP complexes with the inhibitors olaparib (green, 5DS3), rucaparib (orange, 4RV6), niraparib (yellow, 4R6E), and MC2050 (magenta). The NAM-binding site is indicated by the red dashed circle.