FIG. 6.

PRPP binding site in the crystal structure of PurR-cPRPP. The phosphate and pyrophosphate groups of cPRPP bind as expected. The flexible loop is above cPRPP in this view. Structural elements that change in response to cPRPP binding, the flexible loop and Arg160, are drawn in cyan for the free PurR structure. Side chains are also shown for invariant residues Asp203, Asp204, and Lys140, which contact cPRPP. The Arg160 side chain is from the second subunit of the dimer. This figure was prepared with DINO (DINO: Visualizing Structural Biology [2002] http://www.dino3d.org).