Fig 7. Fis binding to Fis-A7 site upstream of the lapA gene.

(A) Protection of the lapA upstream DNA against DNase I cleavage by Fis binding on the sense and the antisense strands. Lines at the right side of the panels indicate the regions protected by Fis from DNase I cleavage at the positions -744 to -768 on the sense strand and -745 to -769 on the antisense strand corresponding to Fis-A7. (B) Gel shift assay of the Fis binding to the lapA promoter DNA containing the wild-type Fis binding site Fis-A7 and mutated site Fis-A7mut. 2 × 10¹⁰ molecules of radioactively labelled PCR products containing Fis-A7 and Fis-A7mut sites were used for Fis binding. Fis was outcompeted from Fis-DNA complex with unlabelled PCR product containing the Fis binding site (LF2) or a PCR product without Fis binding site (RF1). Arrows point to different dissociation of Fis from radioactively labelled DNA in favour of binding unlabelled Fis-specific DNA. Added unlabelled DNA was calculated in molecules. 0.46 μM Fis was used in each reaction mixture except mixtures without Fis in lanes 2 and 12.