FIG. 6.

DNase I footprint of the IHF binding site within the tpl promoter region. The EcoRI-PstI fragment from pUC19-tpl was labeled with ³²P at the 5′ end as described in Materials and Methods. The DNA was treated with DNase I in the presence (lanes 3 to 7) or absence (lane 2) of IHF. The concentration of DNA was 0.7 nM in each reaction mixture. The concentrations of IHF were as follows: lane 3, 9 nM; lane 4, 18 nM; lane 5, 36 nM; lane 6, 72 nM; lane 7, 144 nM. Lane 1 contains the A+G sequence. The region protected by IHF is indicated to the right. The protected sequence reads from the 5′ end (bottom) toward the 3′ end (top) as shown in Fig. 1.