FIG. 6.

NarL insulates pnrf from the effect of IHF III. The figure shows measured β-galactosidase activities of JCB387 cells carrying pRW50 containing different nrf promoter fragments. The pnrf53 and pnrf53/Δ87 fragments contain upstream pnrf DNA from positions −209 and −87, respectively, and all fragments end at position +131 (see Fig. 1). The p124Gp123C substitutions disrupt the IHF III site. Cells were grown aerobically and anaerobically in minimal salts medium, and nitrite was added to a final concentration of 2.5 mM where indicated. β-Galactosidase activities are expressed as nmol of ONPG hydrolyzed min⁻¹ mg⁻¹ dry cell mass. Each activity is the average of three independent determinations. The numbers in parentheses indicate x-fold increases observed due to nitrite.