FIG. 2.

NarX-phosphate accumulation is stimulated by either nitrate or nitrite. Autophosphorylation of membrane proteins from cells lacking the narX expression plasmid (lanes 1 to 3) or harboring the narX expression plasmid and IPTG induced (lanes 4 to 6) is shown. Additions to the phosphorylation assay were as follows: lanes 1 and 4, 10 mM KCl; lanes 2 and 5, 10 mM KNO₂; lanes 3 and 6, 10 mM KNO₃. Reactions were performed at 20°C for 30 s prior to the addition of gel loading buffer. Numbers on the left are molecular masses in kilodaltons.