FIG. 5.

DNA binding patterns of wild-type Xis (A), XisE19A (B), and XisE40A (C). The specific DNA fragments contained the Xis and FIS binding sites, X1-X2-F. The band indicated by an arrow in panel A corresponds to a specific Xis-DNA complex. Nonspecific DNA contained the Int arm-type sites P′1, P′2, and P′3 in place of the Xis and FIS binding sites. The flanking sequences of nonspecific DNA were the same as those of the specific DNA fragment. The final concentration of labeled DNA in each reaction was 1 nM. Nonspecific competitor DNAs were absent from the reactions. Electrophoresis was performed at room temperature. A contaminating fragment migrating slower than free DNA is believed to be single-stranded because it was not retarded by the nonspecific DNA binding mutants.