FIG. 7.

Pulse-chase of phosphorylated NarX. NarX, in the presence or absence of 10 mM KNO₃, was phosphorylated with radiolabeled ATP for 120 s, at which time (arrows) HEPES buffer (to a final concentration of 50 mM) or nonradiolabeled ATP (to a final concentration of 1.03 mM) was added. Aliquots were collected at the indicated time points and mixed with gel loading buffer to stop the reaction. The amount of NarX-phosphate at 120 s (when cold ATP or 50 mM HEPES was added) was estimated by extrapolating from the previous data point. All reactions were carried out at 4°C. Symbols: ⧫, with KNO₃, chased with HEPES; ●, with KNO₃, chased with cold ATP; ◊, without KNO₃, chased with HEPES; ○, without KNO₃, chased with cold ATP.