A. Steady state PII uridylylation state in the absence of glutamine (filled bars) and in the presence of 10 mM glutamine (unfilled bars). PII was at 36 µM, his-tagged altered HD-AA UTase/UR was at 0.8 µM, and the altered D107N UTase/UR was present at 0.8 µM, 2.4 µM, 4 µM, 5.6 µM or 7.2 µM to provide the indicated ratios of enzymes. B. Glutamine signaling by reconstituted UTase/UR-PII cycles containing combination of enzymes. PII was present at 36 µM in all reactions. ■, reactions contained 0.5 µM his-tagged HD-AA UTase/UR and 2 µM D107N UTase/UR. ●, reactions contained 0.5 µM his-tagged UTase/UR (UQ5516) and 2 µM D107N UTase/UR.