Fig. 4

Allosteric site. The allosteric regulatory site of EcKPRS is made up of residues from three different chains of the protein (one chain is colored with green carbon atoms, the second is colored with yellow carbon atoms and numbered with the * symbol, while the third is colored with pink carbon atoms and numbered with the # symbol; oxygen atoms are colored red and nitrogen atoms are colored blue). Binding of the allosteric regulator, ADP (shown here in stick notation with cyan carbon atoms; the position of ADP is modeled from a superposition of EcKPRS with the B. subtilis PRPP synthetase structure, 1DKU), is blocked in EcKPRS by the flexible loop containing residues 101 through 105 (yellow carbon atoms)