FIGURE 4.

A structural model for PAR binding to CHFR. A, model of the binding of a two-adenine-containing fragment of PAR bound to the PBZ motif of CHFR (light blue). The PAR is shown as a ball-and-stick model and is colored as follows: yellow, carbon in adenine groups; white, carbon in ribose groups; blue, nitrogen; red, oxygen; orange, phosphorus. The side chains of the residues that contact PAR are labeled according to the part of PAR they contact (i.e. Ade site 1 or 2 or phosphate (P)), shown as sticks and colored as follows: dark blue, core aromatic residues; cyan, other residues that contact adenine in site 2; orange, residue that contacts phosphate linker. See also supplemental Movie S2. B, schematic diagram to illustrate the contacts between the PAR model and the PBZ of CHFR. C, binding curves derived from surface plasmon resonance data show the reduced binding of CHFR mutants relative to WT.