FIG. 5.

Effects of ATP and tyrosine on DNase I footprinting by TyrR and cAMP-CRP. The DNA used in each case was 1 nmol of a ³²P-labeled EcoRI-PstI fragment from pUC19-tpl. The label was at the 5′ end (see Materials and Methods). The presence (+) or absence (−) of other compounds added to each tube are shown at the top of the figure. When present, TyrR was included at a final concentration of 100 nM, except in lane 7, when the TyrR concentration was 50 nM. The concentrations of other additives were as follows: ATP, 0.2 mM; l-tyrosine, 0.2 mM; CRP, 50 nM; cAMP, 100 μM. The segments protected by TyrR (boxes A, B and C) and cAMP-CRP are indicated to the right. Lane M, A+G standards.