FIG. 5.

ori binding properties of RepB. (A) Competition EMSA with the 200-bp ori fragment as the probe and different amounts of nonspecific competitor salmon sperm DNA (SS DNA). (B) Determination of the minimal amount of RepB required for binding. Different amounts of RepB (5 to 1,000 ng) were added. The molar concentration of RepB in the assay mixture containing 1,000 ng of RepB is indicated in parentheses. The binding obtained with 1 μg of pAB1 extract is shown for comparison. (C and D) Effects of different concentrations of KCl on complex formation by purified RepB and pAB1 extract. In the case of pAB1 extract the extent of complex formation was deliberately maintained at a low level in order to test rigorously the salt resistance of the complex.