FIG. 2.

IHF III activates FNR-dependent transcription at pnrf. The figure illustrates measured β-galactosidase activities of JCB3884 (narL narP) cells carrying pRW50 and containing different nrf promoter fragments. The pnrf433, pnrf53, and pnrf53/Δ87 fragments contain upstream pnrf DNA from positions −302, −209, and −87, respectively, and all fragments end at position +131 (see Fig. 1). Substitutions were introduced into the pnrf53 fragment to disrupt the DNA binding sites Fis II (p175G), CRP II (p153G), IHF III (p124Gp123C), and IHF II (p104p103C). Cells were grown aerobically or anaerobically in minimal salts medium, and 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.