FIG. 7.
Effect of Fis mutations on stimulation of λ phage DNA excision. (A) Schematic diagrams of the λ phage attR region. The top diagram shows the λ phage DNA (thick line) flanked by attL and attR (boxes) and inserted into the E. coli chromosome (thin lines). The attR region is expanded beneath this diagram to illustrate the relative positions of the integrase core region (C and B′) and attR arm binding sites (P1 and P2), as well as the IHF (H1 and H2), Xis (X1 and X2), and Fis (solid box) binding sites. (B) Stimulation of λ phage DNA excision by WT or mutant Fis. The data are based on PFU/ml values obtained from RJ1765 in the presence of WT or mutant Fis and are averages from at least three independent assays; the error bars indicate standard deviations. (C) There was not a general correlation between the relative λ phage DNA excision activities and Kd values obtained from in vitro binding to the λ attRnat site. Use of Kd values for the λ attRpd site did not improve the correlation (not shown).