Binding pocket of ADPR in the NUDT9-H domain presented from different orientations. A and B show the side (A) and top view (B) of the ADPR-binding model in the NUDT9-H domain. The positively and negatively charged residues are colored in blue and red, respectively. (C) The whole view of the binding pocket of ADPR in the NUDT9-H domain. Critical residues for binding are labeled in green.