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 UTase/UR (UQ5516) was at 0.5 µM, and the altered D107N UTase/UR was present at 0 µM, 0.5 µM, 1 µM, 2 µM or 3 µM to provide the indicated ratios of enzymes. B. Glutamine signaling by a reconstituted UTase/UR-PII cycle containing a combination of his-tagged UTase/UR (UQ5516) (0.5 µM) and the altered D107N UTase/UR (3 µM). PII was present at 36 µM.