FIG. 6.

Phosphorylation of NarL by membrane-associated NarX-phosphate. Membrane-bound NarX was first phosphorylated as described in Materials and Methods. To monitor NarX autophosphorylation prior to the addition of NarL, 10-μl samples were taken at 30 s after the addition of ATP to the reaction mixture and transferred to tubes containing 4 μl of gel loading buffer. At 35 s after the addition of ATP (arrows), 1 μl of NarL phosphorylation buffer (A) or 1 μl of NarL protein (B) was added to the reaction mixture.