Figure 4.

Bijvoet difference Fourier maps of the D101L Co²⁺-, Fe²⁺-, and Mn²⁺-HDAC8-M344 complexes (left to right, respectively), calculated with X-ray diffraction data collected at the cobalt edge (7.725 keV), iron edge (7.120 keV), and the copper K_α (8.048 keV) demonstrating the binding of Co²⁺, Fe²⁺, and Mn²⁺, respectively (contoured at 9σ, 4σ, and 4σ, respectively). Anomalous data collected using copper K_α radiation can include signal from Co²⁺, Fe²⁺, or Mn²⁺, but excludes Zn²⁺. In the Fe²⁺-substituted enzyme, uninterpretable difference density is evident (red peak, contoured at 3σ) and may reflect incomplete changes in the metal coordination polyhedron. Protein atoms are color coded as follows: carbon (protein, yellow; ligands, green), oxygen (red), nitrogen (blue). Water molecules are represented as red spheres.